Note: Descriptions are shown in the official language in which they were submitted.
BACKGROIJND OF TE-IE INVENq'ION
l'he present invention relates to optical character
recognition systems and more particularly to an optical
character recognition system which is far less expensive than
those available in the prior art and which is adaptable to
read a wide variety of data formats without requiring the
intercession of a specially trained programmer.
Op-tical character recognition machines are currently
being utilized to read information from original documents
directly into data processing and communication systems. Such
machines eliminate the need for key-to-tape and key-to-disk
eguipment for purposes of data entry since the optical
character recognition machine itself converts the printed data `
into Language suitable for use by the data processor or i~
lS~ computer. ~ j
A typical document to be read by optical character
s~ recognition machine comprises a form having specific
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delineated regions in which data is entered, either by a
typewriter or by hand print. Th~e lines defining the reglons
~20 in which data is to be entered on the form, as welI as
instructions appearing on the form to facilitate use of the
form, is not to be read by the machlne in most cases. In
; order to render this material invisible to the optical
~ ~ I
~ character recognition machines of the prior art, it has been
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25~ ~ necessary to devise special programs which instruct the machine
to only scan predetermined fields in which data is known to be
located. There are at least two severe disadvantages associated
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wi-th this specialized programming approach. For one thing,
the machine mus~ be specially programmed for each different
form because the data format on different forms varies. In
other words, in order to assure that the machine reads only
data, a special program must be devised each time the data
format is changed. This procedure requires a specially
~rained programmer who must be familiar with both the format
to be employed and the particular operation of the processing
circuitry within the machine. For another thing, these
specialized programs provide relatively little leeway for
recognizing data which is not located precisely in the manner
expected by the program. This problem is particularly dis-
tressing in the case of printed forms in which the blank form
has been shifted even a fraction of an inch from the edge of
the page relative to that position which is expected by the
program. Under such conditions, with~the data not in position
as expected by the program, the charaaters cannot be recognized
~ and the document must be rejected by the machine.
; In addition to the problems described above, many
prior art optical character recognition machines are not -
capable of recognizing spaces between characters so that data
which had been spaced on the source document is bunched
together by the machine and rendered difficult to interpret.
Still another problem inherent in many prior art
optical character recognition machines relates to their
1nability to accommodate data lines which are inadvertently
skewed relative to the document page. For example, if the
source document, when typed, was not oriented properly in the
typewriter, a data line may be skewed on the page. Moreover,
in the course of typing, or even hand printing, adjacent
characters are often vertically mis-positioned relative to the
other characters in the line. Under such circumstances the
prior art optical character recognition machines have limited
or no capability of recognizing the skewed or mis-aligned
characters.
It is therefore an object of the present invention
to provide an inexpensive optical character recognition machine
which is readily adaptàble to a variety of data Eormats without
requiring the intercession of a specialized programmer having
knowledge of the internal workings of the machine.
It is another object of the present invention to
provide an optical character recognition machine which is
capable of automatically adjusting the position of a document
in the machine in order that inadvertently mis-positioned data
can be sought and properly positioned so as to be read by the
machine.
It is another object of the present invention to
~provide an optical character recognition machine which is
capable of recognizing individual characters mis-aligned
vertically relative to other characters in a line and which
is capable of accommodating a significant degree of skew in
a line of da-ta being read.
; It is still another object of the present invention
to provide an optical character recognition machine which
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recognizes spaces between characters as such and provides
space character codes to main-tain proper orientation between
` data.
It lS a general object of the present invention to
provide an inexpensive optical character recognition machine
having an extremely flexible data format capacity and which
is not hampered by the aforementioned disadvantages inherent
in prior art optical charac-ter recognition machines.
SUMMARY OF THE INVENTION
In accordance wit~i the principals of-the present
invention an optical character recognition machine is automatically
programmed to accept a particular data format by first processing
a format conditioning document which instructs the machine as to
the locations of data fields on data documents to be read. In
this sense the machine is self programming since each run of
data is preceded by a conditioning document~ Two possible format
modes are disclosed. In a vertical format mode the format
conditioning document includes only a column of line position
marks located on the left hand margin of the document, each
mark designating the location of a data line on the data documents
to be read. Spacing from line to line may vary and all lines
deslgnated by the conditioning document are read on each data
document. In the horiziontal format mode the conditioning
document contains both the vertical format marks in the left
~5 hand margin and horizontal ield delineators within each line
designated by a vertical format mark. ~A predetermined character
designates the beginning of each delineated data field and
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defines the pitch and font for that field. A second pre-
determined character designates the location of the end of
the data field. Only those locations corresponding to the
designated data fields are read on the data documents. Areas
S between the designated Eields are invisible to the machine.
Each line may have a different field length, and the number of
fields may differ from line -to line. With this approach special-
ized programminy by highly skilled personnel is eliminated.
The system includes a line position analysis circuit
which monitors the position of each data sample relative to the
photo-sensitive detecting array. The position of each sample
is utilized ~ predict the position of the next sample so that
a data line which is skewed relative to the data document page
can be tracked during successive samples by the recognition
circuitry. Moreover, if a character or line is found to be
off center in the array relative to the position predicted by
the conditioning document, the document position is automatically
stepped relative to the optical scanning equipment until the
line or character is properly centered in the array.
The system includes an operation mode which requires
no attention by an operator. In thls mode documents which are
not processed because of failure to recognize one or more
characters, are placed in a reject stack or bin. At a later
time the operator, at his or her convenience, can reprocess
these documents and perform any required correction procedure.
An automatic re-scan feature is also provided to permit re-scan
over any line having an unrecognized character. If all
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characters ar~ not recognized on the first scan, the document
page is adjusted to place -the line in the center of the photo-
cell array and the line is re-scanned. If any characters are
not recognized a~ter re-scan, additional re-scans are auto-
maticalLy made with the detec-tion sensitivity adjusted upon each
re-scan. If after a predetermined number of re-scans,
characters are still not recognized, the operator is alerted
to make keyboard corrections. In this mode the machine
automatically displays the unrecognized character to permit
keyboard entry by the operator.
The document transport path is characterized by a
common driving cylinder, driven by a step motor, the cylinder
being arranged to drive two pairs Oe transversely spaced
capstans from th~ same driving cylinder surface. By employing
the common drivé cylinder the possibility of inadvertent skewing
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of a document by the driving mechanism is significantly minimized.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and still further objects, features and
advantages of the present invention will become apparent upon
consideration of the following detailed description of specific
embodiments thereof, especially when taken in conjunction with
the accompanying drawings, wherein:
FIGURE 1 is a functional block diagram of the control
logLc portion of the optical character recognition system of
the present invention;
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FIGURE 2 is a functional block diagram of the recognition
circuitry portion of the optical character recognition system of
the present invention;
FIGURE 3 is a partially diagrammatic front view in plan
of the document picker mechanism employed ln the present invention;
FIGURE 4 is a partially diagrammatic side view in plan
of the document elevator mechanism employed in the present
invention;
FIGURE 5 is a partially diagrammatic front view in
plan of the document transport path employed in the present
invention;
FIGURE 6 is a broken top view in plan of the transport
path of Figure 5;
FIGURE 7 is a schematic diagram of the pneumatic
controls employed in the present invention;
: FIGU Æ 8 is a schematic diagram of the master timing
circuit for the system of the present invention;
FIGURES 9 through 13 are schematic diagrams of the
clrcuitry asoociated with the manual controls of the present
invention;
FIGURES 14 and 15 are schematic diagrams of the master
program counter and associated~control logic employed in the
,
: : system of the present invention;
~ ~ FIG~RES 16 through 25 are schematic diagrams of the
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~25 read and format program counters and associated program control
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~ gic employed in the system o~ the present invent1on;
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FIGURES 26 through 33 are schematic diagrams of the
scan counter, memory data multiplexer circuitry, and associated
control logic employed in the system of the present invention;
FIGURE 34 is a schematic diagram of the diagnostic
control panel employed in the system of the present invention,
FIGURE 35 is a timing diagram illustrating the operating
cycles of the system memory unit,
FIGURES 36 through 42 are schematic diagrams of
add:itional control logic associated with the memory data multi-
plexer circuits employed in the present invention;
FIGURES 43 through 48 are schematic diagrams of the
memory address multiplexer and associated control logic
employed in the system of the present invention;
FIGURE 49 is a timing diagram illustrating the time
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relationship between various signals generated and employed in
the Recognition Circuits of the present invention;
FIGURES 50 through 53 are schematic diagrams of
addltional control loglc associa~ted with the memory address
multiplexer of the present invention;
~ FIGURES 54 through 63 are schematic diagrams of the
~ ff ~ control circuits associated with the memory unit of the present
f ~ invention:
FIGURES 64 and 65 are schematic diagrams of the memory
unit employed~in the system of the present invention;
FIGVRES 66 through 72 are schematic diagrams of the
line position analysis circuitry employed in the system of the
present invention;
.
FIGURES 73 and ~4 are schematic diagrarns of the
interface control logic employed in the system of the present
invention;
FIGURES 75 through 79 are schematic diagrams of
the interface between a magnetic tape unit and the system of
the present invention;
FIGURES 80 through 82 are schematic diagrams of the
interface between the system of the present invention and
keyboard and printer units;
FIGURE 83 is a schematic diagram of a control panel
connector board employed in the system of the present invention;
FIGURE 84 is a schematic diagram of the document
advance counter and associated control logic employed in the
: system of the present invention;
FIGURE 85 is a schematic diagram of the mechanism
connector board employed in the system of the present invention;
; FIGURE 86 is a schematic diagram of the control and
indicator panel employed in the system of the present invention;
. FIGURES 87a through d are schematic diagrams of the
~20 mechanism control panel employed in the system of the present
invention;
FIGURE 88 is a schematic diagram of the scan mirror
motor employed in the system of the present inventlon;
FIGURES~89 through 92 are schematic diagrams of the
25~ quantizer-multiplexer clrcuits employed in the system of the
present invention;
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FIGURE 93 is a schematic diagram of the thirteen
columns of shift registers employed in the recognition circuitry
of the system of the present invention;
FIGURE 94 is a schematic diagram of the details of a
single shift register column employed in the circuit of
Figure 93;
FIGURE 95 is a schematic diagram of an ampli~ier
employed in shift register columns of Figure 94;
FIGURE 96 is a schematic diagram of a decoder and
control logic employed in the recognition circuitry of the
present invention;
FIGURE 97 i5 a schematic dlagram illustrating the
inter-relationship between the shift register columns and
the individual character recognition masks~employed in the
system of the present invention,
FIGURES 98 through 103 are schematic diagrams of the
best match detector circults employed in~the system of the
present invention;
: FIGURES 104 through 108 are schematic diagrams of the
column counter:and~window generator circuits employed in the
system of the present lnvention;
FIGURES 109 through lI8 are schematic diagrams of the
best match store circuits employed in the system of the
:
; present invention; and
FIGURES 119 through 124 are schematic diagrams of the
data control circuits for the recognit~ion circuitry of the
system of the present invention.
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DESCRIPTION OF PREFERRED EMBODIMENTS
I. GENERAL
The optical character recognition system described
herein is part of the same system described in U.S. Patent
Serial No. 3,812,459 issued to John H. MacNeill and Ronald
R.Willey on May 21, 1974, entitled "Improved-OPtical Scan
Arrangement for Optical Character Recognition Systems", and
assigned to the same assignee as the present application.
That patent is concerned with the optical components
employed in an optical character recognition system, the present
application relates to the document handling mechansim, system
control logic, and character recognition circuitry for the same
optical character recognition system. Numerous references made
herein to the optical components of the system relate to the
components in the aforesaid United States Patent 3,gl2,459.
In order to facilitate signal tracing between the
numerous schematic diagrams disclosed herein, each component
bears a reference numeral in which the first digit or digits
correspond to the figure number in which the element or component
is found and the last two digits identify that component or
element in the-figure. An input signal received by an element
bears a parenthesized reference number designating the element
or component from which that signal originated. Likewise an
output signal from an element or component bears the reference
numeral of the component or element receiving that signal.
In this manner, signals and logic operations can be traced from
schematic to schematic and, more particularly from element to
element. The one exception to this approach relates to timing
signals TPA, TPB, TPC, TPD, TPE, and TPF which originate in the
circuit of Figure ~ and are utilized throughout the system
without bearing source or destination reference designation.
Particular voltage levels are not specified herein
unless necessary to an understanding of the system operation.
For ease in reference, however, a convention is employed in which
logic one constitutes a relatively high or positive voltage
whereas logic zero constitutes a relatively negative or ground
voltage.
The drawings disclose the entire system for purposes
of the present application, and signal tracing from drawing to
drawing will provide those of ordinary skill in the art with a
complete understanding of all functions capable of performance
by the system. To facilitate an understanding of the inventive
concepts of the present application, the approach employed herein
in describing the system is to describe in detail only those
portions of the system which relate to the inventive functions,
whereas conventional eunctions and operations performed by the
system are not described in detail. Consequently, while
substantially all of the illustrated components bear reference
numerals, only those components which relate to the inventive
function are described in detail. The description itself is
segmented into four major sections: General Operation (in the
present section); Mechanism Operation; Control Logic Operation;
and Recognition Circuit Operation. These ma~or sections are
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further subdivided into sub-sections in which the various
operations are described in detail.
It will be understood by those skilled in the field
of optical character recognition systems that the present
system approach can be utilized in the recognition of
substantially any standardized font or print. For purposes of
facilitating the present description, however, only the
recognition of OCR-A font is described in detail. The system
capacity to recognize other fonts, including Farrington 7B or
hand written characters, is referred to in passing to the extent
necessary to illustrate the flexibility of the system.
Referring specifically to Figure 1 of the accompanying
drawings, the control logic of the present system is illustrated
in functional block diagrammatic form. Before proceeding with
the detailed description of the Figure 1 block diagram, it is
beneficial to bear in mind that the control logic, in effect,
includes circuitry for performing three distinct programs. These
are: (1) the master program, which is primarily responsible for
document handling in the mechanism; (2) the load format program,
which is performed during specific steps of the master program
; and which is responsible for setting up the system in response to
a format document so that data on documents to be read can be
quickly located and processed, and (3) the read program, which
is performed during specific master program steps and which
2S is responsible for processing data recognized by the system and
effecting various functions required in response to the non-
recognition of data.
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The blocks illustrated in Figures 1 and 2 include
parenthesized designations of the figures in which detailed
circuitry for those blocks may be found.
Mechanism block 101 relates to that portion of the
system which physically handles and stacks documents to be
processed. Operation of this portion of the system, and its
interrelation with the rest of the control logic, is best
described in terms of a transport test mode which is simply a
mode in which documents are transported through the mechanism
to test the mechanism operation. When the start switch and
transport test switch are actuated at control panel 110, the
master program is initiated at the master program counter 103.
Under the control of the master program the document feed shoe
lowers into the document input hopper toward the top document
in the stack. If the top document is below the downward reach
;~ of the feed shoe, the input hopper elevator is automatically
actuated until the top document contacts the feed shoe. When
such contact is made the feed shoe is automatically raised with
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the top document secured thereto by means of suction. Upon being
raised to a predetermined height, the document is delivered
forwardly toward the transport path (or document track) entrance.
When the feed shoe reaches its maximum forward position a first
set of transversely-spaced pinch rollors is actuated to couple
the document to a step motor having as lts primary function the
stepping of the document through the read station where it may
; be scanned by the optical scanning equipment. The document is
released by the feed shoe approximately~30 milliseconds after
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the pinch rollors are activated to assure that the pinch rollors
engage the document before feed shoe release. The feed shoe is
then returned to its rest position.
Actuation pulses are fed to the document feed step
motor to advance the document along the transport path. A
document skew test station is located in the transport path
prior to the read station. The skew station comprises three
photocells arranged in a line transversely to the transport
direction. Only two photocells are actuated, depending upon the
width of the document being transported. If a wide document
is employed, only the inboard and outboard photocell sensors
are active; if a narrower document is employed, the inboard and
intermediate photocells are active. When one of the active photo-
cells senses the document in the transport path, subsequent
steps of the step motor are counted until the second active
photocell senses the document. If the count exceeds a predetermined
count, for example two, the document is considered skewed relative
;~ ~ to the transport path and is to be rejected instead of attempting
to read data from that document. If the count between skew
sensor actuations is below the predetermined count, there is no
skew error and the document is stepped further along the transport
~ path.
I ~ Just down~tream of the read station along the transport
path there is a second set of pinch rollors which is actuable
to engage the document to the document advance step motor. A
photo-sensor associated with this set of pinch rollors automatically
actuates these pinch rollors when a leading edge of the document
16
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has reached this point of the transport path. It is this second
set of pinch rollors which controls stepping of the document
through the read station until the trailing edge of the document
has passed through the read station.
The first and second set of pinch rollors engage
respective capstans or drive cylinders which are all driven by a
common main drive cylinder rotated under the control of the
document advance step motor. The use of a common main drive
cylinder for the capstans eng~ged by both sets of pinch rollors
assures that all drive points for the document are controlled
from a common driving source and thereby minimizes the possibility
of document skewing occasioned by the driving source.
Continuing with the description of the test transport
` mode, the document advance motor continues to step the document
15 ~ along the transport path~ When the trailing edge of the document
passes the skew test station, the system counts ~urther steps
of the step motor until a predetermined number is reached,
this number being sufficient to make sure that the trailing edge
~;~; of the document passes through the read station. When this
20 ~ count is reached an end of document condition is determined and
a reject pinch rollor is actuated which engages the document
to continuously driven belts which feed the document into an
appropriate stacker bin. These functions described above are
controlled by the mechanism block 101, mechanism connector
board 102, master program counter 103, and document advance
control 107 illustrated in Figure 1.
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Lifting of the uppermost document and delivering same
to the transport path proceeds in the same rnanner for the format
load and read modes as in the test transport mode. Departure
f~om the procedure in the test transport mode occurs in the
other modes once the document leading edge reaches the skew
sensor station without detection of a skew error. In the
subseq~lent description, the load format mode is discussed first,
followed by the read mode.
In the load format mode a format conditioning document
is processed by the system and indicates where data fields in
subsequent documents are to be found. Characters located outside
the fields designated by the format conditioning document are
invisible to the system: that is, characters located outside
the designated flelds are simply not processed or stored by the ~ :
system. The load format mode may be a vertical format mode in
.
which the format conditioning document simply comprises a
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vertical column of one or more marks or specified characters,
each designating the location of a line in which data is to be
found in succeeding documents. In this vertical format mode,
the system reads any and all data on an entire line which has
been designated by the format conditioning document.
Alternatively, the load fo~mat mode may be a horizontal format
mode wherein the conditioning document contains both vertical
format and horizontal field designations. On the horizontal
format conditioning document the column of vertical format
markings is present to designate the lines in following documents ~ `
on which data is to be found. In addition speclfic characters
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designating the start and termination o~ data fields on each
data line are provided. Areas between the designated fields
on a data line are invisible to the machine. Every line may
have a different field specified and the number of fields may
differ from line to line.
Assume operation in the vertical format load mode.
Once reaching the skew sensor station without having been
rejected because of a skew error, the document is stepped one
step at a time, with each step being approximately .020 inch.
After each step the optical scanning equipment scans the line
located at the read station. Data, if any, received at photo-
diode array 201 (Fig. 2) is quantized into sixty serial bits on
the MUXSD line by quantizer and multiplexer 202. These sixty
bits represent sixty elements of a vertical slice of a scanned
line on a document. That is, as the optical scanning equipment
scans across the line at the read station, successive vertical
slices, each sixty elements or photo-diodes high, are detected
by the recognition circuits (Fig. 2). If the optical equipment
views a portion of a character, the one or more photo-diode
elements see a black segment which is manifested as a logic
one or high level in the corresponding blt of the sixty bit
serial data stream supplied by the quantizer multiplexer
202. The absence of a character segment is sensed as a
white detected by the particular elements in the photo-diode
2S array, and this white is mani~ested as a logic zero in the serial
data stream. This data stream is applied to the line position
analysi circuitry 118 which, in vert1cal load format, looks
for six blacks or logic one~ in a row to signify that a format
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; mark has been detected. As the data is fed serially to the line
position analysis circuitry 118, this circuitry counts successive
zeros (i.e. white spots detected at the array) preceding and
immediately following the six ~r more consecutive black spots
signifying a vertical format mark. The purpose of this is to
determine when the format mark is centered vertically in the
array. If the number of white spots above the format mark is
greater than the number of white spots below the format mark,
the mark is low in the array and the line position analysis
circuits commence to advance the document one more step, after '~
which another analysis is made. This analysis for detecting ~ , '
centering of the mark is continued until the mark is in fact
centered. While this is occurring the document advance counter ''
counts the numb,er of steps which the document has been advanced
:'
`from the top of the document to the centering of the first
detected mark. This count in the document advance counter 107 ~ '
is then connected through the memory data multiplexer 116 to , '
the vertical format portion of the memory module ll9 under the
' control of the memory address multiplexer 117 and the memory
control circuits 115. The document is then advanced a pre- '
determined number of steps and line position analysis is repeated
until another mark is detected and centered. The number of
steps between successive detected vertical format marks is
stored in the memory module 119 in similar fashion to permit the
i system to properly position subsequent documents so that each
data line may be scanned. When the trailing edge of the document
passes the skew station the system recognizes an end of document
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condition and a special character signifying this condition is
stored in the next vertical format section of memory 119 to
indicate tha-t no further lines are to be found on documents
being read. The line position analysis circuitry 118 performs
numerous other functions during other operating modes, but
during load format operation its primary function is mark
centering as described above. From the foregoing it will be
seen that successive sections of the vertical format portion of
memory module 119 contain the locations of successive lines on
each document at which data to be read appears.
During vertical load format the document advance
counter 107, as mentioned above, keeps track of the spacing
between successive lines containing data fields. The document
advance counter is a seven bit counter and is therefore
capable of registering 128 steps. Since it is possible that
two successive lines of data are separated by more than 128
steps, it is necessary to incorporate a flag into the memory
along with the count of 128, each time a larger spacing occurs
between data lines. This flag signifies to the system, during
the read mode, that the document should be advanced 128 steps,
after which the next incremental count should be retrieved from
memory to control further document stepping. If the following
number in the vertical format portion of the memory is zero,
the system interprets this as an indication that the end of
document has been reached and no further lines of data are
present in the document.
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When the processing of the vertical format conditioning
document is completed, the vertical format conditioning document
is rejected from the mechanism and placed in a stack. The next
document in the stack can then be read according to the format
delineation designated by the conditioning document. Actually,
the mas-ter program is arranged to automatically proceed to the
read program operation upon receiving the next document after
the format conditioning document has been processed. During the
read program operation the system pulls successive numbers from
the vertical format section of the memory, advances the step
motor according to these numbers, and reads the data on the
appropriate lines of the document.
The memory data multiplexer unit 116 controls the
entry of ~our data sources into memory module 119. One source
is the document advance count from document ad~ance counter
107. A second source is the recognition data received from
the data control unit 208 in Figure 2, which data corresponds
to the character recognized by the recognition circuits. A
third data source is the data entered from the keyboard and
printer interface 104. The fourth data source is the horizontal
scan position count which is generated within the memory data
multiplexer circuitry and therefore does not appear as an
input source in Figure 1. The memory module 119 itself is
divided into three portions: one portion receives data coming
from the recognition circuits or the keyboard; another portion
receives vertical format data; and the third portian receives
horizontal format data. For each memory address portion there is a
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different address counter provided. The memory address multi-
plexer 117 includes a data address counter, a vertical format
address counter, and a horizontal format address counter.
Depending upon the nature of the write cycle, the memory
S address multiplexer 117 and memory data multiplexer 116 control
entry of information into the proper portion of memory module
119. Actual multiplexing is accomplished at the multiplexer
circuits 116 and 117; however control signals for operating the
multiplexer circuits originate in the memory controls circuitry
115. The memory controls circuits designate to the memory
module ll9 and to the multiplexer circuits the nature of the
memory cycle (i.e. vertical format entry, horizontal format
entry, data entry, etc.) to be performed. In the vertical
format load mode, after an address is written into memory,
the vertical format address counter is incremented. When the
memory cycle is complete the document is advanced and
another line position analysis is performed to look for the next
vertical format mark. When this mark is centered the document
advance counter contents aFe entered into the memory address
designated by the current count in the vertical format address
counter. When the end of the document is reached, the document
;~ advance counter is reset and an additional memory write cycle
is initiated wherein all zeros are entered into the next vertical
format location of the memory.
There are eighty six memory positions in the vertical
format section of memory. As the vertical format load mode
proceeds, the system continuously monitors the number of
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vertical format words which have been entered into memory. If
the number of vertical format entries reaches 86, the system
interprets this as a format error. Theoretically, if the
longest document is fourteen inches in length, and if six lines
per inch is the most dense spacing permissible, only eighty four
vertical format marks can possibly be detected. Thus, if
eighty six marks are detected, a malfunction, such as a double
pulsing of the address counter, etc., has occurred and an
error is registered.
In the case of the horizontal format load mode, the
system looks for vertical format marks and centers such marks
in the same manner as is done in the vertical format load mode.
However, upon centering each vertical format mark, the line
corresponding to that mark is scanned by the optical scanning
system for the purpose of detecting beginning and end of
field characters. Scanning is effected by energizing the
cIutch and brake coils of the scan motor, thereby coupling
the mirror cam to the motor to permit the mirror to inltiate
scan. There is an aperture in the cam which controls the
beginning of line (BOL) photocells. When the cam is at its
home position (l.e. looking at the left hand edge of the paper),
the BOL photocell detects a light through the cam aperture.
After the clutch and brake are energized, the cam moves
approximately 7 to 10 after which the aperture de-energizes
the BOL photocell. This 7 to 10~basically defines the left
hand margin reference point on the document page. When the
BOL photocell is turned off, the horizontal scan position counter
in the data multiplexer circuit 116 begins counting timing
24
,
pulses provided at the rate at which vertical slices or samples
of characters are registered at the photo-diode array during
a scan. The scan motor is synchronized with the basic system
clock so that the BOL photocell may serve as a reference point
from which horizontal position of characters can be measured~
During a scan in the horizontal format mode the system
awaits recognition by the recognition circuitry of a
specific beginning of field character. Upon recognition of
such character, the horizontal scan count corresponding to its
horizontal scan position is written into the horizontal format
portion of the memory. In addition the lower order bits of the
recognized character are written into the same portion of the
memory. Scanning continues until a second and subsequent
characters are detected and recognized, the scan position and
low order bits of the~e characters also being written into the
memory. The first character represents the beginning of a
horizontal field; the second character represents the end of
that field. Subsequent characters represent beginning and end
o~ field markers in alternation, it being possible to place
substantially any number of fields in a line. If an odd number
o~ field characters are recognized a format error is indicated,
since each field must have a beginnlng and end of field
character. After all of the fields have been registered the
document is advanced until the next vertical format marX is
detected and centered~ Before the system actually begins
looking for the next vertical format line, the document is
stepped a sufficient number of steps to remove the previous
' ~ ' .
,',
r
.
', ,' :
.. , : , , ,, . . . :
' ,, , '' " . . " ~' ' ' ' " ', ~ . ' , '
vertical format mark and associated line out of the array.
When this is done the ~ocument is stepped one step at a time
and a line position analysis is performed at each step to
look for the vertical format mark. In this manner each line,
and the fields on each line,are recognized and their locations
stored in the memory to permit the system to look only for
these fields when reading a document.
As successive data fields are detected on the horizontal
format conditicning document, their positions are stored
successively in the horizontal format portion of memory. The
address of the next available section of the horizontal format
portion of memory is continually maintained in a separate
register so that when the horizontal format conditioning docurnent
has been completely processed, this separate register has stored
therein the address of the next available section of the
horizontal format portion of memory. During the read mode,
as the location of each data field is retrieved from memory,
the address of that section of the memory from which the data
field location is retrieved is compared against the contents
of the special register. In this manner the system is able
to automatically determine when the last data field has been
read from a document.
As mentioned above, when a character representing the
beginning of a data field is detected during a scan, the lower
order of bits of that character as recognized are stored in the
horizontal format portion of memory. Actu~lly there are two
low order bits of the recognized ch~racter so stored~ These
26
.. . ~, ,
two bits are utilizecl to specify the font to be utilized for
characters which will be read in that field. The two bits
provide a combination of four different conditions, thereby
permitting four different fonts to be specified, Naturally the
number of bits can be increased if desired so that the system
may be programmed to recognize substantially any number of
fonts. In addition, the beginning of field character utilized in
the conditioning document is selected in accordance with the
font -to be used in the field identified by that character.
Moreover two bits may be stored at the end of the field count
to designate the pi-tch (characters per inch) of the utilized
font; of course the particular beginning of field character em-
ployed would be coded to represent pitch. For example, the OCR-A
font may be provided at l~ pitch or 8 pitch, so that the stored
bits from the recognized character distinguish to the system
which pitch is being used in the designated fields. In the
vertical format load mode, the control panel format switch
identifies which font is to be u-tilized during a reading mode.
Considering now the read mode for documents which
.
have been preceded by a vertical format conditioning document,
;~ each document to be read is picked and delivered to the transport
path as described in relation to the test transport mode. The
document is stepped through the read station in acaordance with
;the vertical format data stored in the vertical format portion
of memory 119. Specifically, the first vertical format
information stored in the memory represents the number of
~; ~ steps required to advance the document, from the top of the
:
27
~Q~3~7
document, to place the first line to be read at the read station
of the transport path. This is done automatically, with the
characters being processed in the manner described subsequently
in relation to Figure 2. When the line has been completely
S processed the document is automatically stepped by the number
of steps indicated in the nex-t section of the vertical format
portion of memory, whereupon the next line to be read on the
docurnent is automatically positioned at the read station. The
actual operation carrying out this function is as follows.
After a line is to be read (or when the leading edge of the
document reaches the skew station), the count stored in the
next section of the vertical format portion of memory is
withdrawn from the memory and placed in the memory output data
register in memory address multiplexer 117. The ones complement
of that count is preset into the document advance counter 107.
The document advance motor is then stepped, with the document
advance counter contents being incremented upon each step, until
the count in the document advance counter 107 is all ones. At
~ this point the document has been advanced the required number
of steps to bring the line to be read to the read station.
When this line reaches the read station the clutch and brake
for the scan motor are eneryized to move the cam and mirror to
begin scanning. The recognition circuits begin operating, and
upon recognizing data, supply data to the memory data multiplexer
along with memory write commands.
If a character is not recognized the system generates
a character substitution code, which as described herein is the
28
31~
ciode for an underline. Thè underline code and the read error
flag are placed in the data memory position corresponding to
the character location at which the unrecognized character was
found. The system automatically places the horizontal scan
count, corresponding to the location of the unrecognized
character, immediately adjacen-t the error flag in the data
memory~
The recognition circuits continue to recognize or
not recognize characters as the line is scanned. In the system
as de~cribed, there are eighty four positions for recognized
characters in each line; theoretically there should be only
eighty characters on an eight inch l~ne at the maximum pitch.
When the scanning mirror reaches the right hand margin of the
paper the read enable mode terminates. If at this ti~e fewer
than eighty four write commands have been received from the
recognition circuitry, the memory controls unit 115 automatically
:, . : .
generates memory fill characters which are stored in memory -
to fill the eighty four posltions on the memory line.
After the line has been read and the memory fill cycle
has been completed, the system determines if a read error flag
flip-flop has been set during the scanning of the line, indicating
that an unrecognized character was found during the previous
scan. If the flip-flop is not set, indicating that a line has
been completely recognized, that line is automatically transferred
out o~ the memory module to the output device (printer, tape,
~ 4~',f While data is being transferred to the output device
the control logic automatically steps the document to the next
,.. .... . .
29
'
. . .
.. . ... . . . . , . :. . .. .
:; ' : ~ . . :
. - . . . . .. .
9~7
line according to the vertical format information stored in
memory. Depending on the speed of the outpu-t device the scanning
mirror may be back at the left hand margin of the document before
the output data of the previous line has been completely trans-
ferred to the output device, in which case the system waits
until the output data has been completely transferred.
I f one character or more has not been recognized in a
scanned line, a complete re-scan of that line is performed. If
all of the characters in the line are recognized during the
re-scan, operation proceeds as described above with the line of
data transferred to the output device. If a character is still
not recognized after the re-scan, the threshold level of the
output amplifiers from the photo-diode array is adjusted to
render these amplifiers more sensitive. A second re-scan is
then performed and if all characters are recognized the data
is transferred to the output device as with a normally recognized
line. If again there is an unrecognized character in the re-scan
c~
line, the threshold level of the array amplifiers is P~ again.
This adjustment of the threshold level of the array amplifiers
permits lightly printed characters to be more readily recognized.
Specifically, gray spots on the document wQuld tend to be
recognized more as black rather than white as the threshold
~; of the ampli~iers is increased. In the system as described as
many as four re-scans at adjusted threshold levels of the
amplifiers may be effected. Importantly, in those re-scans
in which the threshold level is adjusted, the recognized data
from previous scans is not disturbed; rather, the stored
unrecognized character flags are sought and their scan location
determined. When the scan mirror is placed at the scan location
of the unrecognized charac-ter, a read enable condition is
initiated. Importantly however the read enable relates only
to those characters which have not,been recognized previously.
IE all of the characters are recognized after four or fewer re-
scans the system proceeds as previously described.
If there is still at least one character that is not
recognized after four re-scans- at adjusted levels of the array
amplifiers, there are three possible alternatives which can
be pre-selected by the system operator. One alternative is
the reject mode which causes the document to be automatically
rejected if there is any character not recognized'after a fourth
re-scan. A second alternative is the error substitution mode
wherein the data for the line is automatically transferred to
the output device with an underline code replacing any un-
recognized character. The third alternative is the error
correction mode wherein the scanning apparatus automatically
returns to the unrecognized character which is then projected
onto a viewing screen for display to the operator. A cursor
mark points to the unrecognized character,on the screen. The
~ ~ operator can then enter directly into the system from keyboard
j : ~
111 the character which has be,en unrecognized by the system.
This data passes through data multiplexer I16 into the memory
25~ ' at the proper character location selected by the memory address
' ~ multiplexer 117. The error flag for that character is then ,~
automatically deactivated and the system continues processing.
31
"
::: - . . . . . . .. .
: .: . '. . '' . . . ., : . ...
:'' ',:,.':" .. - , .' ., . ,. . : .. , '
If more than one unrecognized character is present in a line,
this process is repeated -to permit keyboard entry of each of
the unrecognized characters. Once the last character in the line
has been corrected the system automatically searches through
the memory to make sure that all characters have been recognized
and data is transferred to the outpu-t device.
The line position analysis circuitry 118 also comes
into play during read mode operation. Specifically, this
circuitry is continuously determining whether or not a line is
high or low in the array and approximately how high or low it
is. If a line is determined to be high or low, the document is
stepped forward or backward to try to bring that line as close
to being centered in the array as possible. In addition the
line position analysis circuitry 118 utilizes the position in
the array of a detected character slice to predict the position
in the array of the next character slice.
Operation in the read mode, after a horizontal format
condition1ng document has been processed, lS similar to processing
after a vertical format conditioning document has been processed
insofar as positioning the document relative to the read station
is concerned, Once the first line to be read is positioned at
~- the read station, the first scan count stored in the horizontal
portlon~of memory is retrieved under thè control of the memory
address multiplexer 117. The count is stored ln the horizontal
25~ ~ format ~ield pos~ition register in the memory data multiplexer
116. The scan mirror is then positioned in accordance with the
-
retrieved count, after which the next stored horizontal scan
:
:
,
'~
,. ',. .
.
''' , "'., , : :
~a~4~7 `
'count is retrieved and placed in the same register. This second
retrieved scan count ccrresponds to the end of the field to be
read. A read enable cycle is initiated and continues until the
~ scan count corresponding to the actual mirror position is the same ~-
as the stored scan count corresponding to the end of the data
field. When the read enable cycle is terminated, the next stored
scan count, corresponding to the beginning of the next data field,
is retrieved and stored in the register and the scanning mirror
is positioned accordingly. This positioning of the scan mirror
0 in accordance with the stored scan counts continues until all ~ `
data fields in the line have been read. In the meantime the
recognition circuits supply reeogni~ion data and initiate memory
write cycles to store the data being recognized. As each field
is stored, the data control unit 208 in the recognitlon cireuitry
'S generates an end of field character, which in the system as
deseribed is the tab character. This end of field character is
. ~ , . .
placed in memory to serve as a field separator so that suecessive
data fields can be automatically spaced at the output device.
` Referring specifically to Figure 2 of the accompanying
:~ ~
~0 drawings, the recognition circuitry of the optical character;;~; recognition system are illustrated in functional block form~
~; The basie timing for the recognition circuits is illustratedin the timing diagram of Figure 49. The basic timing for the
recognition circuits Is controlled by the multiplexer counter
~25 loeated in the quantizer and multiplexer 202. The multiplexer
~ eounter defines one timing interval, designated herein as
-~ MUX interval, for each six successive master timing pulses.
'. "
33
:, . : :
/
There are sixty four MUX intervals for each recognition circuit
cycle. During one MUX interval in each sixty four interval
cycle the sixty channels of data detected by photo-diode array
1 201 is sampled and stored in pa~allel in a register in quantizer
and multiplexer unit 202. This data is then transferred in
par~llel to a shift register from which it is shifted out
serially during the remaining sixty three MUX intervals (i.e.
one ~hift per interval) to thirteen columns of shift registers
in unit 203. The thirteen columns of shift registers effectively
) serve to reconstitute the samples or vertical slices of data
characters to permit recognition of these characters by mask
circuitry at unit 204. The mask circuitry comprises weighted
signal lines connected to the various shift register stages
to provide sixty four different output signals, each representing
~; a different character mask. If the character in the thirteen
shlft register columns corresponds to a character for a particular
mask, the output signal from that mask has a higher amplitude
output signal than any other mask output signal. The determina-
tion of the highest level mask output signal is made in the best
!0 match detector 206 which in turn provides a seven bit ASCII code
output signal representing the recognized character. In addition
the best match detector examines the amplitude level o~ the
highest mask output signal and provides a four bit number
representative of that amplitude. At the best match store unit ;
207, the four bit correlation function representing the amplitude
of the highest level mask output signal is quantized into sixteen
levels. If the function i5 at the highest or next highest level,
34
.. : .. . - : .
,- . . . . . .
.
~l~4~ 7
-- the best match store unit considers recognition to have been
successful and the seven bit character code is transferred
through the data control unit 208, along with the OCRW memory
: write command,to the control circuitry for storage in memorymodule 119. If the correlation function falls within the third,
fourth or fifth highest possible levels, recognition is not
automatic; instead, the mask output signal must coincide in
time with a character window generated at the column counter
and character window generator 205. The character window is
0 synchronized to the character spacing for the particular format .
being read and therefore serves to identify those times when a
character should be present for recognition. If no character
dt all is detected within the window lnterval, data control unit
208 generates a space character for storage in memory.unit 119.
If thc four bit correlation function is at the third, fourth or
: fifth highest level and there is no time coincidence with the
` ~ window 1nterval, a non-recognition condition exists and is so
indicated by setting the read error flip flop at data control
~ unit 208 which in turn provides the read error flag (RERF) signal.
0 If the correlatlon function is at the sixth or seventh highest
: level, and this level is maintained at the end of the window
.,`. ~ .
~ interval, a match is detected and the character is stored in
.. . .
~ memory.
. If the correlation function for the character in the .. ~.
'S mask is below the seventh highest level, but a character is in
. fact in the mask, a read error condition is signified by setting
.
~ the read error flip-flop in data control unit 208. As described
:. 35
,
,: .
,
~ ' . .~ . , . . ; ~
. .
~ .
in relation to the control circuits in Figure 1, if the read
error flip-flop is set during a scan, the line is re-scanned
automatically one or more times. :'
I . The individual circuits representing the blocks in
; Figure 2 are described in greater detail hereinbelow at which
time other functions for these circuits are further described.
.~ . .
'
' ' : ~ '
.:
- ' ~ ' ''~
: ,~
: 36
; . , ' ' ' ', ' ' ' ' , :
II. MECI-IANISM
The mechanism portion of the present invention serves
the following functions: automatically raising and lowering
a stack of documents to place the uppermost document of the
stac~ in position t.o be picked and transported to be read;
automatically picking the uppermost document from the stack and
delivering it to a transport path; and automatically transporting
a document along the path so that it may be read and later
delivered to a suitable storage location. The drawings relating
to these functions are Figures 3, 4 and 5.
II (A) . DOCUMENT PICKER
Referring specifically to Figure 3 of the accompanying
drawings, -there is illustrated the essential features of the
picker mechanism of the present invention. A stack 3.01 of
individual documents is placed on a vertically ad~ustable elevator
.~; platform 302. The picker mechanlsm, generally designated by the
~ numeral 300, is located above the document stack and is arranged
i
to dellver the uppermost sheet of the stack to a document trans-
,~ : port path 303. The picker mechanism includes a feed shoe 304
I ~
.~ 20 supported at one end of a horizontally extending hollow support
~rod 305. ~ir passages 306 are defined internally of feed shoe
304 and communicate with the interior of hollow rod 305. A
5.
i` : , :
~, ~ plurality of longitudinally extending openings 307 are defined
in the lower surface of feed shoe 304 and communicate with
25 ~ internal passages 306. The end of rod 305 remote from feed
shoe 304 is selectively connected: to a negative pressure or
''' C:~ Q,~` S
;: : vacuum source which draws air in through ~ ~ 307 and
': :
37
. .,~
, ~
passage 306 and creates a negative pressure at the lower surface
of feed shoe 30~.
An air motor 308 is arranged to selectively translate
a horizontally extending push rod 309 along its longitudinal
axis. A control arm 310 is coupled at 311 to the remote end of
push rod 309. Control arm 310 depends vertically from coupling
311, the latter being a pivotal coupling which permits relative
rotation between control arm 310 and push rod 309. Pivotal
coupling 311 is not fixed to the mechanism frame so that it is
free to translate horizontally as push rod 309 is driven by air
motor 308.
The lower end of control arm 310 is pivotally engaged
to one end of a crank arm 312. The other end of crank arm
312 is secured to rod 305. Control arm 310 extends
somewhat below rod 305 so that control arm 310 and crank arm 312
join at a location below rod 305. Control arm 310 is pivotally
, secured to the mechanism frame at a location 313 intermediate
`~ its remote end. This pivotal engagement 313 permits horizontal
translation of push rod 309 to be reflected as oppositely
directed horizontal translation of rod 305. Specifically, if air
'~ motor 308 translates push rod 309 to the left as viewed in
i Figure 3, control arm 310 is rotated counterclockwise about
pivot point 313. The lower end of control rod 310 is thus
driven to the right and pulls on crank arm 312 which in turn
:~ :
.~ 25 :translates rod 305 to the right.
,~ ~ A ~orizontally extending support arm 314 lS pivotally
~' secured proximate one of its ends to the mechanism frame. The
.
38
:
~'t' J
'
~L~4~
pivotal engagement between the frame and support arm 314
is designated by -the numeral 315. At the opposite end of support
arm 314 there is provided a pin 316 which extends horizontally in
a direction perpendicular to support 314. Pin 316 engages a
- slot 317 defined through the upper end of a vertically disposed
lift arm 318. The lower end of the lift arm is pivotally secured
at 319 to rod 305 at a location intermediate the two ends of
that rod. The intermediate portion of support arm 314 is secured
to the armature of a picker solenoid 320. Solenoid 320 is
arranged so that its armature may be selectively reciprocated
vertically. When armature 321 is released, support arm
314 is pivoted counterclockwise (as viewed in Figure 3)
abo~lt pivot 315. Pin 316 thereby raises lift arm
318 by means of the engagement with slot 317 and causes feed
shoe 304 to pivot upwardly about the remote end of rod 305.
When armature 321 is pulled downward, pin 316 is lowered and
permits lift arm 318 to drop. This lowering of lift arm 318
;~ results in a lowering of feed shoe 304 as rod 305 pivots
I
clockwise about its remote end.
Pin 316 on,horizontal support arm 314 is also arranged
to close a ~icroswitch 322 when armature 321 of picker solenoid
320 is in its extended position. Closure of this switch thus
indicates that picker shoe 304 is raised. Another pin 323 extends
perpendicularly from push rod 309 and is arranged to close a
microswitch 324 when push rod 309 is retracted by air motor 308.
Lift arm 318 carries a switch-closing member 325 which is
,
39
.: ' ;
arranged to close a microswitch 326 when rod 305 is driven to
its extreme right-most position as viewed in Figure 3; this
position corresponds to a feed complete position for feed shoe
304, in which position a document has been delivered to transport
path 303.
Lift arm 318 is sufficiently long to restrict the delivery
stroke for feed shoe 30~ to a s-traightlnJriG~Ilt~i-line~ parallel to
path 303,thereby assuring proper entry of a picked document onto
the transport path 303. As illustrated in Figure 3, the transport
surface of delivery path 303 slopes slightly upwardly from the
entry edge in a downstream direction. The forward edge of the
: lower surface of feed shoe 304 is correspondingly sloped ti.e.
the height of the feed shoe decreases in a forward direction)
so as to promote smooth entry~ of a document onto the transport
path 303 between the two sloped~surfaces. Specifically, the
sloping portion of feed shoe 304 and the entrance of transport
:
path 303 are contoured:such that a document delivered by the
feed shoe contacts the delivery path downstream of the sloping
portion whereupon it is grabbed~by drive rollers as described
:
;~ 20 ~ subsequently in relation to Flgure~5.: A~plurality of vacuum
~ ; ports:or apertures 330 are deflned through;the transport surface- of transport path 303 slightly;upstream of an apex 331 which:defines the break~between the~sloped and flat portions of the
~ transport path.
: 25 : Apertures 330 are~connected to a source of negative
pressure or vacuum~and serve-to detect the presence~of two
documents inadvertently~being delivered to the transport path
':
., .
: 40
'' ~, ' ' ~ :
.: . . . .
by the feed shoe. More particularly, if the feed shoe delivers
only a~single document to the transport path, that document is
delivered downstream of the location of ports 330. A second
document however contacts the sloping portion of the transport
path and blocks air flow being suctioned into ports 330. Its
blockage is sensed in a manner described subsequently and results
in stopping of the document feed process.
Portions of the sloping leading edge of the transport
path, at locations upstream of ports 330, are recessed to define :
flow channels 332. These flow channels communicate with a source
of positive pressure, causing air to flow toward the storage bin
301. This air serves to riffle the documents being lifted by
shoe 304 during delivery of a document to the transport path ~ :
and thereby aids in separating two or more documents which ;.
have inadvertently been lifted by tn~ feed shoe. In this regard
it is to be noted that feed shoe 304 actually makes contact
.with the uppermost document in the stack at a level substantially
~ .
below the leading edge of transport path 303 so t.hat the riffle
air delivered from flow path 332 does not interfere with the
` ~. t ' O QQ~i:~ suction required at ~h~nme~ 307 to lift the uppermost document.
. 1
~ ~. Additional riffle air flows can be employed in relation to
. .,
~ document stack 301 to facilltate separation of individual
:~ : documents an~d alignment of documents relative to the stack and
.
. the transport path 303.
.ii For purposes of understanding the operation of the
mechanism illustrated in Figure 3, it is necessary to point
., out that feed shoe 304 is illustrated in approximately a half
. . O
41
'' '' ', ' , : '.
stroke position such as it would assume in the midst of delivering
a picked document to transport path 303. When the mechanism is
at rest, feed shoe 304 is displaced substantially to the left
of the position illustrated in Figure 3. When at rest, push rod
309 is retracted, drawing pivo-t poi~t 311 to the right and causing
the lower end of control arm 310 to be displaced to the left.
The forward or right-most end of feed shoe 304 in this position
is free to drop into the bin containing document stack 301.
Assuming for the moment that the uppermost sheet in
stack 301 is at a high enough level to permit it to be picked
by feed shoe 304, a typical operation of the mechanism of Figure 3
will be described. First the normally extended armature 321
of picker solenoid 320 is retracted, permitting lift arm 318 to
fall and cause rod 305 to pivot clockwise about its left end
!
15 ~ untll the lower surface of feed shoe 304 contacts the uppermost
document in stack 301. Assuming the vacuum source to be in
~ operation, suction at ~*i~Ym~ 307 in the lower surface of feed
j ~ ~ shoe 304 causes the uppermost sheet in stack 301 to attach to
the lower surface of the feed shoe. An interlock, to be
described subsequently, indicates that a document has blocked
307 and causes picker solenoid 320 to release its armature
321. When the armature is thus extended control arm 318 is
raised to in turn raise feed shoe 304 to a height slightly
.. : :
above the entry point to transport path 303. Air motor 308 is
then operated to extend push rod 309 and thereby pivot control
arm 310 about pivot point 315. Control arm 310 thus drives rod
305 to the right so that feed shoe 304, with a document attached,
42
. . . ~ ,~., -
", , , ",
is -translated over -transport path 303. At the end of the feed
stroke, swit~h-ac-tuation member 325 operates microswitch 326,
resulting in the disengagement of the document from feed shoe
304 so that it may be driven along the transport path in a manner
to be subsequently described. Push rod 309 is then retracted
and feed shoe 304 is returned to its ready position above document
stack 301.
The various interlocks and controls operated in response
; to actuation of switches 322, 324 and 326 are described
subsequently, the present description is concerned only with
- the operation of the mechanism per se.
Since for practical reasons the vertical motion of feed
shoe 304 must be limited, it is necessary to raise and lower
elevator platform 302 to assure that the uppermost document in
stack 301 can be engaged by the feed shoe. In order to
determine when it is necessary to raise platform 302, there is
provided a flange 327 extending from feed shoe 304 and arranged
to block an air-pressurized sensing port 328 when feed shoe 304
is in ltS lowermost position. The back pressure resulting
upstream of port 328 is used, as described subsequently, to
~` provide a control signal for operating an elevator mechanism
which raises and lowers the platform 302.
II (B) . ELEVATOR MECHANISM
The elevator mechanism for ralslng and lowering platform
302 is illustrated diagrammatically in Figure 4 of the accompanying
drawings and is generally designated by the reference numeral 400.
Platform 302 lS supported horizontally by a vertlcally extending
43
'' , ;
-
lift member ~01 which is adapted to slide vertically along
suppor-t memher 402 under the control of a pair of rolling bellows
type air cylinders 403. Only one such air cylinder 403 is
iLlustrated in Figure 4: the other air cylinder is located
on the opposite side of the elevator unit, into the plane of
the drawing, so that raising and lowering forces can be applied
simultaneously and e~ually on both sides. The description of
mechanism 400 which follows relates -to only that side of the
rnechanism which is visible in Figure 4; it being understood
that corresponding parts are provided on the opposite side
(into the plane of the drawing) to simultaneously effect
identical purposes.
Air cylinder 403 includes a push rod 404 which is
secured at its end to an intermediate location along pivot arm
lS 406. One end of pivot arm 406 is pivotally secured to vertical
support 402 and is constrained from vertical movement. The
opposite end of pivot arm 406 is pivotally secured to a control
arm 407 which has one end pivotally secured to lift member 401
~` ~ and its other end pivotally secured to a pivot plate 408.
Plvot plate 408 extends into the plane of the drawing to the
~ other side of the elevator mechanism; plate 408 also extends
- ~ in height to a fixed support member 409 where it is pivotally
:
secured and constrained from either horizontal or vertical
motion.
~ 25 A second lever arm 410 is pivotally secured to support
-~ member 402 at one end and to a second control arm 411 at its
. .
other end. Lever arm 410 is substantially identical to lever
~. :
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44
, . j~'!.,
: '. , : .
' ' ' ' ' , . ' ' .' " ' ,
'' ' '' ' ' ' ,' " " '. ' ~ '
, ....................... . . ' ,
arm 406 except that it is not driven by an air cylinder and is
located above lever arm 406. Control arm 411 is pivotally
secured at one end to lift member 401 at a location substantially
above that at which control arm 407 is pivotally secured. The
other end of control arm 411 is pivotally secured to the top end
of a further plate 412, the other end of which is pivotally
secured to support member 409.
The double Watts linkage mechanism 400 provides a
mechanical advantage which magnifies the displacement of push
rod 404 to provide a greater vertical displacement of lift
member 401 and platform 302. Specifically, as armature 404 is
extended, lever arm 406 tends to rotate in a counterclockwise
direction about its end fixed to support 4020 The resulting
upward force exerted on control arm 407 tends to pivot that
control arm in a clockwise direction about its end secured to
pivot plate 408. The end of control arm secured to lift member
401 tends to raise the lift member and platform 302. Pivot plate
408 swings outwardly (i.e. counterclockwise) about its point of
attachment to support member 409 as lift member 401 is raised.
A similar operation ensues for lever arm 410, control arm 411
and pivot plate 412. Specifically, as lift member 401 is
. .
raised by control arm 407, control arm 411 tends to pivot
in a clockwise direction about its point of securement to pivot
- plate 412. The pivoting action of control arm 411 however is
constrained by a lever arm 410 to follow a similar pivot path
to that followed by control arm 407. Pivot plate 412, in
accommodating the pivoting action of control arm 411, tends
~O~ 7
to swing outwardly (i.e. clockwise) a~out its point of attachment
to support member 409.
Lowering of the elevator mechanism proceeds in an
~ inverse manner upon retraction of push rod 404 by air cylinder
~03. Specifically, as push rod 404 is retracted, lever arm 406
tends to rotate in a clockwise direction about its end fixed to
support member 402. A resultant downward force is exerted on
control arm 407 which pulls lift member 401 downwardly and imparts
a slight counterclockwise rotation to control arm 407. In
) accommodating the downward movement of the lift member, pivot
plate 408 swings inwardly (i.e. counterclockwise) about its
point of attachment to support member 409. The lowering of
lift member 401 tends to rotate control arm 411 about its end
secured to pivot plate 412, the pivoting of controL arm 411
; being constrained by lever arm 410. Pivot plate 412 swings
inwardly to accommodate the motion of control arm 411.
The double watts linkage arrangement for elevator
mechanism 400 is a low friction device which utilizes low
tolerance parts. Amplification factors depend on locations
~D of pivot points but typically are on the order of 4 to 1.
' ` ~ ,: '
II(C). DOCUMENT TRANSPORT PATH ~;
The transport path 303 referred to in relation to
Figure 3 is illu:trated in detail in Figures 5 and 6 of the
; accompanying drawings. The purpose of the transport path is to
properly position a document in order that successive lines of
. :'
. , ~ , ' :
,
46
.'~ ~ ' ,.
.' , '' ' ' '., , ' . ' , , , , , ~il'
-,, , :
.
.
47
text may be scanned and read, and then to eject the document
into either of two storage bins. The transport path is
essentially flat throughout most of its length; however, the
document entrance section slopes upwardly toward the downstream
end of the track until reaching apex 331. As described
previously, feed shoe 304 functions to deliver a document to
the transport path such that the document first contacts the
transport path in the region of apex 331 and downstream of double
document sensing ports 330. To continue the transporting motion
of the document along the transport path from the point of deliv-
ery by the feed shoe, a pair of transversely spaced capstans or
drive rollers 501 is provided. These drive rolIers are posi-
tioned such that their peripherles are oriented substantially
tangentially to the plane of the transport path at a loctation
substaDtially at apex 331. Both the drive rollers 501 are
frictionally driven by the same cylinder 503 which is driven
by step motor 500 to advance the document in small increments
on the order o~ .02 inches per step. Cylinder 503 has a
constant diameter throughout its length (i.e. - into the plane
~ of the drawing in Figure 5) so that both drive wheels 501 are
driven at the same speed. The use of a common drive for both
transversely spaced drive wheels S01 signifi~cantly minimizes
the possibility of a document becoming skewed while being
transported along the transport path. A second set of drive
~S wheels 504 is transversely~spaced ln a manner identical to
47
a~
~L~)4'~7
drive wheels 501 and communicate tangentially with the trans-
port path surface at a location somewhat downstream of drive
wheels 501. Drive wheels 504 are also both driven by master
~rive cylinder 503 so that all drive wheels 501 and 504 are
driven at the same speed.
Drive wheels 501 can only drive a document along
the transport path when respective pinch rollers 505 are
positioned in peripheral engagement with the drive wheels.
Pinch rollers 505 are selectively translatable into engagement
and out of engagement with drive wheels 501 under the control
of solenoid 506. Likewise, pinch rollers 507,under the control
of solenoid 508, are positionable to render drive wheels 504
capable of imparting forward motion to a document along the
transport path.
Three pairs of drive wheels 509, 510 and 511 are
successively spaced longitudinally along the transport path.
These drive wheels are rendered operative by respective pinch
roller pairs 512, 513 and 514, respectively, which are in turn
controlled by respective solenoids 515, 516 and 517. The
}unction of drive wheel pairs 509, 510 and 511 is to rapidly
eject a document from the transport path after the document
i ~ .
- has been scanned and read by the system. To this end, drive
~ wheels 509, 510 and 511 are driven relatively rapidly at the
.. . . . .
same speed by means of a common motor 518.
A location along the transport path between drive
wheels 501 and 504 is designa~ed as the read station 520,
A line of text material appearing at this location isscanned
-' ' . .
~8
~.. ,.. - .
- , ~ ,",
, ,,. , ' , .' . , ~ ' , . ' , . ,: "
by the optical equipment and processed by the recognition
circuitry. Scanning is in a direction into the plane of the
drawing of Figure 5.
Slightly downstream of drive wheels 501 there are
located three transversely spaced skew detector stations. Each
skew detector station includes an,assembly 521 in which is
loc~ted a light-emitting diode and a photocell. Light emitted
by each light-emitting diode (LED) is directed downwardly toward
a respective prism 522 located in a plane of the transport path.
The transversely spaced prisms 522 serve to reflect light from
the light-emitting diode back toward the photocell in assembly
521 unless the light path between assembly 521 and its corres-
ponding prism 522 is'blocked by a document in the transport
path.
Dep,endinq on the width of a document being read,
two of the three light-operated skew detectors are
rendered ~perative. Although the logic involved in the actual
skew detection is described in greater detall in relation to
the control logic portion of the systems, it should be mentioned
here that the philosophy behind the skew detection is based
on the fact that a straight or unskewed document should block
all of the operative skew detectors simultaneously. If only
one of the skew detectors is blocked it is an indication that
the document is skewed in the transport path and the transport
procedure is automatically stopped. As a practical matter the
system permits step motor 500 to step once between blocking
of first one and then another of the skew detectors; however
if two steps of motor 500 occur between blocking of one skew
.
, ' 49
3~
detector and another, -transport is automatically stopped.
The skew detector thus serves to prevent jam-ups
which might otherwise occur if a skewed document were trans-
ported along the transport path. Of course skewing of a docu-
ment is significantly minimized, as described below, by virtue
of the fact that drive rollers 501 are driven at precisely the
same speed so that no net turning moment is applied to the
document during transport.
The system is arranged so that drive rollers 501
; 10 never drive a document at the same time as drive rollers 504.
To this purpose solenoid 506 is actuated (to thereby engage
drive wheels 501 and pinch rollers 505) when the document is
`~ delivered to the transport path by the feed shoe ~ of
Figure 3, solenoid 508 remains unactuated at this time. The
document is stepped by drive wheels 501 through the read
station 520 and upon reaching drive wheel 504 actuates a
second feed capstan sensor comprising assembly 523 and prism
5240 Assembly 523 is similar to assemblies 521 in that it
contains a light-emitting diode and a photocell; prism 524
is similar to prisms 522 in that it is located in the trans-
port path plane in alignment with the assembly 523. When
the document blocks the second feed drive sensor (as is more
clearly described in relation to the electronics portion of
~ .
the system), solenoid 508 is deactuated resulting in disengage-
ment of pinch rollers 505 from drive wheels 501 and a termina-
tion of the driving capability oE drive wheels 501. After
.
j 50
. ~
' ,' ',........ ' , ,: ~' ' ' , '' ' :'
. .
.. . . . . . .
: . ', . , . - ,: . . . .
. .
r.'~
4~
a short delay, on the order of 30 ms, solenoid 508 is actuated
to bring pinch rollers 507 into engagement with drive rollers
504 so that stepping of the document is continued under the
control oE the drive rollers 504.
A further optical sensing unit is located in the
transport path proximate the first ejection drive wheels 509.
This sensor includes assembly 525 and the prism 526 and provides
an indication to the system that the document has entered the
ejection region of the transport path. This indication is
10 stored in the system to acknowledge the fact that the document
can be rapidly ejected from the transport path when necessary
by actuating solenoids 515, 516 and 517. Such ejection normally
takes place when reading of the document has been completed
however ejection of the document may also be effected under
15 other conditions.
After being ejected from the transport path the
document may be automatically delivered to either a normal
stacker bin 530 or a reject stacker bin 531. The entrance
to the stacker bin section is monitored by a stacker entry
20 detector comprising assembly 527 (LED and photocell) and
prism 528. The stacker entry detector functions to turn off
.. .. .
the transport mechanism in the event of a document jam in
the process of document entry into one of the stacker bins.
Specifically, the time dur~ing which a transported document
blocks the stacker entry detector is monitored in the electronics
` portion of the system. If this time exceeds a predetermined
time interval, a document jam is assumed and do~ument trans-
` port is terminated~ Likewise a photo-sensitive jam detector
51
.' - ' '' , . ' . . ..
'. ' ,.' ' ' ,,',
(including LED and photocell assembly 534 and prism 531) is
located at the entry to normal stacker bin 530 to monitor the
time required for a document to enter the normal stacker bin;
and a detector (including LED and photocell assembly 536 and
S prism 537) is located at the entrance of the reject stacker
bin 531 to monitor the time required for document to enter
the reject bin. I~ the time required for a document to com-
ple-tely enter either bin exceeds a predetermined time, transport
is terminated since a jam is assumed.
A document upon being ejected by drive wheels 509, 510 and
511, is driven into the stacker region by first stacker drive wheel
532. Drive wheel 532 is also driven by motor 518. Downstream
of the stacker region entry detector (assembly 527) and prism
528) there is located a pivotable bifurcated document steering
member 538,whlch,during normal ejection, is positioned in radially
spaced relation from drive wheel 532 so as to guide a document
driven by drive wheel 532 into the normal stacker bin 530.
Member 538 is pivotably controlled by solenoid 539. When the
` latter is actuated, steering member 538 is pivoted counter-
.
clockwise (as viewed in Figure 5) so that the upstream end of
~,
bifurcated steering member 538 pivots into suitably provided
; recesses in the periphery of drive wheel 532 (as indicated
, ~ in dashed lines in Figure 5). In this positlon steerin~ member
'
538~blocks entry of the document into the normal stacker bin
530 and instead steers the document further along the transport
path towards drive wheel 533 which directs the document into
the reject stacker bin 531. Control of solenoid 539 is deter-
mined by the document reject logic described herein in relation
to the electronics portion of the system.
.
52
.
. . : : . , .
.
II (D) . PNEUMATIC CONTROL SYSTEM
The pneumatic controls employed in the system are
illustrated schematically in Figure 7 of the accompanying
drawings. A source of pressurized air (P+) is applied to a
pressure regulator 701 from which it is delivered to the
various controls. One flow path includes a valve 702 which
is opened and closed ~y the solenoid (to be described subse-
quently) which is actuated when it is desired to operate air
cylinder 308 to initiate a feed stroke for feed shoe 304.
Specifically, when a feed stroke is to be initiated, valve
702 is opened and pressurized air flows through flow
restriction 703 to actuate air cylinder 308.
Another path for ~he outflow from regulator 701
includes a pressure isolating flow restrictor 704 connected
in series with a check valve 705 and an actuable valve 706.
~ut~iow from tne actuable valve 7û~ îs divided into two flow
paths which supply respective air cylinders 403 to actuate
the elevator mechanism illustrated in Figure 4. A pressure
tap is connected between flow restrictors 704 and check valve
705 to supply air under pressure to orifice 328 which as
described in relation to Figure 3,is employed as part of a
height sensing arrangement for feed shoe 304. Specifically,
flange arm 327 secured to the feed shoe is lo~tered with the
feed shoe and blocks outflow from orifice 328 when the
shoe has reached its lower limit position. When orifice 328
is unblocked, a portion of the air flow through restrictor
704 is bled off via orifice 328. This creates a relatively
low pressùre at the upstream side of check valve 705, which
.
53
:,
'' '.'' '.' '' '" '
pressure is insufficient to actuate air cylinders 403. In this
condition,therefore,the air cylinders 403 remain unactuated and
the elevator mechanism of Figure 4 remains stationary. When
orifice 328 is blocked by flange member 327, the pressure up-
stream of check valve 705 is increased sufficiently to provide
a significant air flow to air cylinders ~03 and the elevator
mechanism is raised. Valve 706 acts to selectively inhibit
elevator operation under the control of circuitry to be des-
cribed subsequently.
From the foregoing description it is seen that
lowering of the feed shoe 304 into the document bin continues
until such time as the feed shoe encounters the uppermost
sheet of the stack,or flange 327 blocks bleed flow through
orifice 328, whichever occurs first. If the uppermost document
in the stack is encountered before orifice 328 is blocked, the
~ elevator mechanism remains stationary. The uppermost document
; is picked and delivered to the transport path in the manner
to be described subsequently. If on the other hand the bleed
orifice 328 is blocked by ~lange member 327 before feed shoe
304 encounters the uppermost sheet in the stack,air cylinders
403 are actuated to raise the elevator unti~l such time as the
documents in the stack raise the feed shoe suffioiently to
unblock orifice 328. At this time the feed shoe is in
contact with the uppermost document in the stack and this
document is picked and delivered to the transport path.
Still another parallel path for outflow from pres-
sure regulator 701 terminates in a nozzle 707 located ln a
vacuum chamber 708. Specifically, nozzle 707 is directed to
54
Lh,~ ., ~ ~1, . ~
.
.: . . . .
to issue air flow Lnto the funnel-like upstream end of a venturi
tube 709. The region surrounding nozzle 707 and the entrance
to venturi tube 709 is enclosed to define vacuum chamber 708.
The relatively high velocity air issued from nozzle 707 aspirates
air Erom vacuum chamber 708 to provide a relatively low pressure
condition therein. The downstream end of venturi 709 is connected
to supply riffle air to riffle channel 332 located at the
` entrance to the transport path.
Vacuum chamber 708 serves as the vacuum or low pressure
source for the system. A flow passage 710 supplies flow to
~, chamber 708 from either of flow passages 711 or 712, depending on
the position of valve 713. When valve 713 is in the position
illustrated in Figure 7, suction is applied to channel 307 in
the feed shoe 304 via tube 305 to permit the feed shoe to lift
the uppermost document from the stack. A vacuum-actuated switch
~; ~ 8724 is actuated when suction applled to the feed shoe is blocked
by a picked document. This switch actuation enables the feed
shoe to be raised so that the document may be fed to the
transport path.
Valve 713, which is solenoid-controlled in the manner
to be described in relation to the system electronics, may also
be positioned to bring flow passage 712 into flow communication
wlth vacuum chamber 708. Under such circumstances suction is
1~ applied to document level detectors in each of the normal and
1 25~ re~ect stacker bins 530 and 531 via respective flow restrictors
714 and 715; in addition suction is applied via flow restrictor
.
716 to the double documen-t sensing port 330 located proximate
the entry portlon of the transport path.
4~
A vacuum switch is associated with double document
sensing port 330. ~his vacuum operates when suction is
a~>pLied to sensing port 330 and the latter is blocked. Acuation
of the vacuum switch is reflected in the electronics of the
system to stop the feed process. Likewise, vacuum switches are
associated with each of the stacker bin and document level
detectors so that a full stacker bin results in stopping the
v system and prevention of jamming.
"'~i ~ '
'I .
, I .
56
,' ,
III. SYSTEM ELECTRONICS
To facilitate understanding, the description of the
electronics portion of the system is subdivided into two major
sections: the Control Loyic Circuitry and the Character
Recognition Circuitry. The Control I.ogic Circuitry relates to
system timing, storage and utilization of recognized characters.
The Character Recognition Circuitry, as the name implies, receives
data resulting from the optical scanning of a document, recognizes
such data, and provide electronic signals representative of the
recognized data for use by the Control Logic ~ircuitry. In the
following description the Control Logic Circuitry is described
first, followed by the Character Recognition Circuitry. For
ease in understanding, the following description is not
structural such that each sec-tion refers to one specific drawing
figure, rather, the description is structured in relation to
3~ : : i
I different system functions such that each section of the
description involves a number of different drawing figures.
`1 `
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,~ ~
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,
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57
.
,
~ ~4;9~7
III(A). CONTROL LOGIC CIRCUITRY
A.1). TIMING CIRCUITRY
A timing circuit, which generates all timing pulses
for the system, is illustrated schematically in Figure 8 of
the accompanying drawings. The primary timing source is a
crystal-controlled oscillator 801 which provides a series of
pulses at a frequency of 5.898 MHz. The train of master
timing pulses is applied to an eight bit counter 802 which
is wired to a preset logic circuit 803 so as to provide
output pulses at a frequency of 159 KHz with a pulse width
of 2,04 ~ s, Specifically, counter 802 is preset to a count
of 104 and counts to a count of 140 before being preset.
This results in a divide-by-37 operation with the last stage
of the counter remaining high or binary one between the counts
128 and 140. This signal is applied to gate 7801 ih the
magnetic tape interface unit of Figure 78,
The pulses from oscillator 801 are also applied to
flip-flop 804,acting as a divide-by-2 circuit,which applies
pulses at a 2.949 MHz frequency to flip flop 805. During
normal operation flip flop 805 is maintained in the clear
condition by the output signal from the inverter 806 so that
output pulses appear at the Q output terminal of flip flop
. . .
805 at the same frequency as the input pulses applied to
flip flop 805. Inuerter 806 receives the HALF SPEED signal
from ~lip-flop 2531, 2532 during the Error Halt mode. That
is, the half speed operation is initiated during a manual
entry of characters which have not been recognized automat-
ically by the system. At such time the output signal of
58
-' ,: ' . ~ :.' ' . '
inverter 806 removes the clear signal from flip ~lop 805 which
then ac.s as a divide by 2 circuit. Under these conditions the
Q output siynal from flip flop 805 is a train of pulses at a
frequency of 1.475 MHz.
S The Q output signal from flip flop 804 and the Q
signal from flip Elop 805 are applied to NAND gate 807. During
normal operation the CLOCK ou-tput pulses from NAND gate 807
I appear at a frequency of 2.949 MHz. During half speed operation
the output pulse frequency is 1.475 MHz.
Flip flops 808, 809 and 810, and AND gates 811, 812
and 813 are interconnected to provide a divide-by-6 counter
circuit. The counter circuit is preset to start its count at
2 and continues until count 7 before automatically presetting,
thereby skipping counts zero and 1. This counter circuit operates
on the pulses provided by NAND gate 807 and provides pulses
which are utilized by a decoder circuit which includes NAND
` gates 814, 815, 816, 817, 818 and 819. These six NAND gates
i .
\ decode the six respective states of the counting circuit and
provide six corresponding timing pulses TPA, TPB, TPC, TPD~ TPE
and TPF. Each of these timing pulses is also connected to
~ ~ a respective inverter buffer 821 through 826 which provides
; ~ the TPA through TPF pulses. These six-phase master timing
~ ` pulses serve to subdivide consecutive~master timing
I ~ ~ intervals into SIX discrete subintervals, the master timing
~ intervals being repetitive at a frequency of approximately
492 KHz in normal operation and 246 KHz during the half speed
operation mode. The TPA through TPF timing pulses are
170 nanoseconds in duration with a spaclng of 170 nanoseconds
59
. . .
- . , . P.:.'. ~ -. .. ~
': ' . ' ~. ' . . '
..
.' ,
9~47
off time between phases. In other words, the time between the
leading edge of the TPA pulse and the leading edge of the
TPB pulse is 340 nanoseconds.
Four-bit counters 827, 828, 829 and 832 are driven
by timing pulse TPF and operate as.free running countdown cir-
cuits for various timing purposes. The various reference
designations associated with each of counters 827 through 832
rel.ate to Model 74161 manufactured by Texas Instruments, it is
to be understood however that other counters can be connected
to perform the same functions described herein.
NAND gate 833 is driven by timing signals from
counters 827 and 828 and in turn drive~ inverter 834. The
output signal from inverter 834 in turn is applied to AND gate
835 along with the TPF timing pulse to provide a VSCP pulse
on every 64th TPF timing pulse. This VSCP pulse is connected
. : to the circuits of Figure 81 and is utilized in the timing
for interface with demonstration printers.
,:
; The flip flop 836 is connected to counter 829 and
: receives the TPA timing pulses to provide a pulse once during
;~
: 20 every 2048 TPA pulses. Since the TPA pulse repetition rate
is approximately 492 KHz, the Q output signal pulse rate from
flip flop 836 is approximately 240 Hz. This signal is applied
~ to the drive circuits for the scan synchronous motor in
'¦~ Figure 85 where it is divided by four to generate a 60 Hz scan
control signal synchronized with the ~asic master timing
oscillator 801. The scan motor utilized ln the system optics is
'1 :
.
,
: 60
' ~ . 5
~ ~ , ~'' ,' ' , : ' '; ' '
,.'
.
~9~P147
a 900 rpm synchronous hys-teresis motor and is geared down at a
125 to 40 ratio to provide a 4.8 rps rate at the drive shaf-t to
the scan mirror. A single lobe cam is utilized to drive the
scan mirror which therefore also has a rate of 4.8 scan cycles
per second. This is to be compared to the fact that the photo-
cell array in the Character Recognition circuits is sampled
once every 64th TPF pulse. For this scan rate and for the
timing described, the recognition system is able to take 1600
samples per scan cycle. The maximum distance between center
lines of OCR-A characters is 0~055 inch. If, as assumed here,
this distance is divided into eight sample periods, each
sample element which is 0.006875 inch. The cam causes the
mirror to scan a line 8 1/4 inches long. Wlth 0.006875 inch
per sample, this requires 1200 samples and therefore 1200/1600 x
~15 360, or 270 of the cam revolution is required for reading
a line. The remaining 90 are used for transition at the end
of a scan, returning the mirror to the left hand margin of a
document page, and providing a 12 dwell at the left hand
.
margin of the clutch/brake start/stop operation.
Counters 830 and 831 provide resettable timing pulses
for the master and read program counters. The signal ATCL is
a pulse which is generated each time either of the master or
read program counters is advanced, and has the purpose of
resetting counters 830 and 831, as well as flip-flops 1001
l~ ~25 through 1006 in Figure 10. Counters 830 and 831 count the
;1 240 Hz pulses provided by the counter 829. The Qc output
61
.'~', ,., :' '' "
~4~7
terminal of counter 830 is designated TC30 and goes high on
four counts and low on eight counts. This signal is applied
to flip-flop 1004 in F'igure 10, causing signal DL 30 to go
high after eight counts, or approximately 32 ms after the
:
ATCL goes high. The TC3.7 signal from the Q~ output terminal
of counter 831 goes high at 16 counts and low at 32 counts and
sets flip-flop 1006 in Figure 10. The TRC signal provided at
the QD output terminal of counter 831 goes high at 128 counts
and low at 256 counts to set flip-flop 1005 in Figure 10 after
. 10 one second. In addition flip-flops 1001, 1002 and 1003 in
Figure 10 count four TRC pulses so that flip-flop 1003 is set
after 4.0 seconds. These three flip-flops, once set, remain
set unti1 they are cleared by the next ~TCL.
.,
. ~
. ~
`
~,
62
',: ?~
,
- ` ~
47
III(A.2) CON~ROL PANEL AND MANUAL CONTROLS
The control panel illustrated in Figures 86a and 86b,
contains various switches for control of the system and various
display lights for indicating system status. The control panel
con`tains -the following rotary switches which affect the indicated
functions, modes and operations:
Operate Mode Switch 8601 - 3-position, two pole.
l. Error Halt Mode
2. Reject Mode
3. Error substitute Mode
Document Width Switch 8602 - 3-position, two pole.
1. Wide
2. Medium
3. Narrow
Font Style (Format) switch 8603 - 4-position, two pole.
l. Handwriting
2. OCR-A ) Vertical format only
3. Farrington 7B
, 4. Mixed - Horizontal format
.; ~20 ~ Lines per inch switch 8604 - 2-position, two pole.
~; 1. 6 lines per inch
2. 3 lines per inch
The following momentary switches are also on the
control panel: ~
~ 25 Lower Hopper 8605 Re~ect Document 8610
! ~ . Format Load B606
~; Start 8607
63
.i~ .
.
'
Stop 8608
Repeat Line 8609 Clear 8614
The system status indicator lamps are illustrated in
Figure 86b and are lit under conditions corresp~nding to the
nomenclature for the respective driving signals in that Figure.
Each lamp is also actuable by the LAMP TEST signal which permits
the operator to light all lamps to determine if any are burned
out. The driving signals for the lamps are derived from
circuitry in Figure 83.
The connector board for the control and indicator
panel is illustrated in Figures 83a and 83b. To insure correct
operation, signals from the rotary switches in Figure 86a are
stored in latches 8301-8308 during MPSP time of the master
program. MPSP is high when the system is in stop condition and
the master program counter (Flg. 15) is at MPSO. Should the
operator change a switch setting while the s~stem is running, the
unchanged latch output maintains the previously set operating
condition. If any switch is changed when MPSP is low, comparison
circuits 8311 through 8318, which compare the switch settings
:
and latch conditions, operate via gate 8319 to set an Operator
` Error ~lip-~lop comprising NOR gates 8309 and 8310. This
operates circuitr~ in Figure 9 to generate a stop signal which
~ stops the system. The Operator Error indicator lamp is actuated
,l to indicate to the operator that the desired swltch settingshould be made and the start switch re-actuated. The Error
indicator light is reset by the start switch a~d the storage
latches 8301-8308 are restored to the proper switch settings.
ll
- 64
~" :,
The rotary switches 8601-8604 are wired to provide
a binary code output. This binary code is stored in the latches
8301-8308 and is then decoded to provide the desired control
signal. This use of latch circuitry permits a reduction in the
S number of wires required at the control panel.
All signals from the switches are termina-ted with
pull-up resistors to -~5 volts.
The circuit of Figure 83b receives input signals which
represent the various conditicns of the system and which serve
to actuate the various system status lamps. These signals go
through a set of gates and/or inverters and are then applied to
the lamp circuits in Figure 86b. The various input signals are
discussed as they are generated in relation to the master program
` counter description.
Most of the manual control functions are implemented
., .
by circuits in Figure 9. The start-stop circuitry includes
gates 901 and 902, which form a stop flip-flop; flip-flop
~ .
903 is the start flip-flop. Signal PR is a "power on;
~ clear" signal which initially puts the system in the stop
-~ ~ 20 condition.
Operation of the start switch 8607 causes STSW to go
.i .
high and STSW to go low, res;etting the stop flip-flop 901, 902.
Start flip-flop 903 remains in the reset condition so that STR
is high. AND gate 905,with high MPSO aDd STR inputs, provides a
~25 high MPSP signal for setting latches 8301-8308. NAND gate 906,
with MPSP and, the output of the stop flip~flop high, provides
a low SCLR, which is the start clear signal. Gate 907
: , :
. .' ' ' . ' , .
.9~7
effectively "or's" the PWR ON CLR and CLSW (clear switch 8614)
signals to provide PR. PR is "or'ed" with SCLR at gate 908 to
provide signal MCLR which is the master clear signal for the
system. Therefore each time the start switch is operated and
the unit is in the stop condition (STR being high) the system is
set to a clear condition. When the start switch 8607 is released,
STSW goes low and STSW goes high. Gate 904, with STSW low and
a low Erom the stop flip-flop 901, 902, enables the setting of
the start flip-flop 903 at the next TPF clock pulse. With
flip flop 903 set, STR is high and STR is low, thereby inhibit-
ing MPSP and SCLR.
Various stop signals are "or'ed" by Gate 902 to return
the system to the stop condition. These are
SPSW - stop switch 8608 signal through Gate 1301
Label - generation of a tape label prevents the system
from being put into the start condition (signal
from tape lnterface, Fig. 76, via inverter
1302, gate 1301)
FMERSP - Format error; stop (signal from read and
¦ 20 ` format program counter, gate 2101.
, I .. . .
OPRER - Operator Error signal from Fig. 83a.
¦ HE - Detected Document Supply Hopper Empty Signal
.
,~ (from 1401, 1402).
! _ ~
DCERR - Document error indication, which includes
;~ 2S Pick Fail, Document ~am and Skew Error
(from 1403~.
.
.
~ 66
;
, ~ " , ,~. , . ' :
The primary function of the staxt flip-flop 903 is to
enable the Master Program counter (Figs. 14, 15) to advance from
the MPSO to the MPSl state. Once the counter has advanced, the
system follows its normal sequence of operations even though
the start flip-flop may be reset.
Gates 909 and 910 form a flip-flop to control the
elevator valve 706 with signal HRVS HLD via inverter 911 and
driver 8709. When this line is low, elevator valve 706 is ener-
gized and allows the elevator 400 to raise the stack of documents
to be picked. A Hopper Empty (HE), Document Error (DCERR) or a
signal from the lower hopper switch (LWHPSW) during MPSP time,
sets the flip-flop 909, 910 and the HRVS HLD signal goes high.
With the elevator valve de-energized the air holding up the
elevator is allowed to bleed off and the input hopper returns
to its lowest position. When the start switch is operated the
~` MCLR signal from inverter 912 resets flip-flop 910, 911 and
.
~ seals off the bleed valve.
.~
Gates 913, 914 form a flip-flop for format entry
control.~ Operating the format enter switch 8606 to provide
~i 20 signal LFSW during MPSP~sets this flip-flop via NAND
gate 915. It is reset by the PR signal (CLEAR) and by the
master program signal MPS6, which occurs after the conditionlng
document has been completely processed.
.':,
~ ,
~ ~ .
,
' ~ '
67
: .:
: ,~ br~
.7
III(A.3) TRANSPORT PATH CONTROLS
Control over the mechanism protion of the system is
effected at the mechanism panel which is illustrated schematic-
ally in Figures 87a through 87d of the accompanying drawings.
Equipment at the mechanism panel permits control over the follow-
ing: the document picking mechanism; read station document
transport; document eject and output stackers; scan motor and
clutch/brake; photocell sensor stations; switch sensor station;
solenoid control; display mechanism for manual entry of data;'
and pneumatic assembly for air pressure/vacuum system.
The mechanism panel assembly includes a plurality oE
solenoid drivers 8701 through 8709 which are illustrated in
Figure 87a of the accompanying drawings~ These drivers are used
to control various system solenoids and valves illustrated in
-~ 15 Figures 87b and 87d of the accompanying drawings and described
'~ ~in the following paragraphs:
Driver 8701 operates the picker solenoid 320 illus-
trated in Figure 87d. This is the solenoid which selectively
, ~
lowers feed shoe 304 to reach for the next document in document
j 20 stack 301
., ~
Driver 8702 controls the shoe vacuum~valve 713 illus-
,~ trated in Figure 87d. Valve 713 is a solenoid valve which gates
' '1
vacuum from vacuum chamber 708 to the feed shoe 304 via tube
305.~ Suction channels 307 in,the bottom surface of feed shoe
25~ 304 allow the vacuum to;grab the uppermost document in stack 301.
Driver 8703 controls the picker feed valve 702 illus-
trated in Figure 87d. When picker feed shoe 304 has lif~ed
a document and has returned to its highest position, solenoid
valve 702 is energized automatically by virtue of the fact that
68
.
' .', ' , , ,
'
7 `- ~
microswitch 322 is actuated. This permits air pressure from
the air assembly to actuate air cylinder 308 and cause the feed
shoe and the document to move forward toward the transport path.
~ ~ -e,~e ~ ~ z ~
The e~e~qrz~S~ valve 702 permits air pressure to escape from
aiL cylinder 308 and a spring returns the feed mechanism to its
initial position
Driver 8704 controls the first feed solenoid 506
illustrated in Figure 87b. When feed shoe 304 has moved to its
extreme feed position (to the right in Figure 3), microswitch 326
is actuated by member 325. At this time the FFS solenoid 506
is automatically energized to engage the leading edge of the
document between pinch rollers 505 and drive rollers 501, the
latter being driven by the document step motor 500. Solenoid
506 remains energized until the leading edge of the document
is sensed by photocell assembly 523 located at the second set
of pinch rollers 507.
Driver 8705 controls the second feed solenoid 508
illustrated in Figure 87b. The second set of solenoid operated
pinch rollers 507 is`located just downstream of read station
520. When the leading edge of the document passes this set
of pinch roll~rs, photocell assembly 523 automatically energi~es
solenoid 508 and de-energizes solenoid 506. Rollers 507 engage
the document to the drive roIlers 504 and document stepping
continues, under control of the master, read and format programs.
Driver 8706 controls the eject solenoids 515, 516, and
517 illustrated in Figure 87b. After a document has been read,
~; solenoid driver 8706 actua~es the three eject solenoids whichare evenly spaced along the transport path. These solenoids
` operate pinch rollers 512, 513 and 514, respectively, which
~i 69
47
engage the document to spaced belts which are continually driven
by rollers 509, 510 and 511. This moves the document to the
stacking mechanism at which a second set of continually moving
belts is located. These belts are always in contact with the
respective drive rollers. Solenoid 508 is turned off 30 milli-
seconds after the eject solenoids are deactuated.
Driver 8707 controls the stacker select solenoid 539
illustrated in Figure 87b. Solenoid 539 controls document
steering member 538 which is used to steer the documents to
either the normal stacker bin 530 or the reject stacker bin
531. When solenoid 539 is de-energized, the document is steered
into normal bin 530. When solenoid 539 is energized the docu-
ment is steered into reject bin 531. Appropriate timing inter-
locks are provided in order that the steering member 538 cannot
be moved while a document is progressing through thé stacking
mechanism. The steering condition is set before the document
is ejected.
~; Driver 8708 controls the track motor relay 8710 which
; in turn controls the track motor 518, as illustrated in the
I
~, 20 Figure 87b. The eject and stacker drive belts are moving con-
tinuously, driven by an electric motor 518. If a document jam
is detected, relay 8710 is energized by driver 8708 to remove
1 ~
the primary power from motor 518. After the operator has in-
~ vestigated the cause~of the jam and cleared any jammed document,
;~i ~ 25 the next operation starts,which de-energizes relay 8710 and
permits motor 518 to run continuously again.
, ~ : :
Driver 8709~controls the elevator valve 706 illustrated
in the figure 87d. Document stack 301 is raised or lowered by
:
'
o
the elevator mechanism of Figure 4 which is controlled by two
air pistons 403. Valve 706 is an air escape valve which is
closed to prevent bleeding. When valve 706 is closed, the
elevator may be raised by controlled air pressure from the air
assembly as illustrated in Figure 7. This air pressure is
supplied when the feed shoe 304 is lowered to reach for a docu-
ment. If the uppermost document of the stack is too low, the
feed shoe extends far enough down to cause member 327 to block
outlet 328. The resulting back pressure actuates air pistons
403 until the top of the stack of documents raises the feed
shoe and outlet 328 becomes unblocked. A check valve 705 and
solenoid valve 706 prevent air from escaping air pistons 403.
The elevator can only be lowered by de-energizing valve 706
and permitting air to be bled from pistons 403. This is
accomplished automatically under certain conditions,such as
the hopper empty condition. A manual switch is also provided
to permit operator-controlled lowering of the elevator. The
solenoid valve is automatically re-energized when the start
switch is operated.
Control over the document step motor 500 is
illustrated in Figure 87b and 87c. The document step motor,
which controls document advance through read station 520, is
a bifar wound 4-pole step motor. It includes 200 steps per
revolution ti.e., 1.8 per stepl, and the diameter of the
drive capstan is chosen so that each step of the motor advances
the document 0.0208 inches. The motor is bidirectional and
can bé selectively reversed to perform a fine line adjustment when
it is necessary to center a line of data at the read station. The
71
'' ', " " , " ' ' ' ' '' ' ~ . '," ' "' . ~ ' ' "' ' ' ~ ' ', . '
~' " " ',''' ' "" ' ' ~ .', ' ' ' "", ' . " " "' ' '" '" ' ' . ,
9~7
primary step control~is the signal DCMT which is generated a~ .
described in relation to Figure 84. A reverse direction con-
tr~l signal (DOwN-COUNT) is generated during fine line adjustment
as described in relation to Figure 72- These two ~ignals are
5 1 utiliz~d in th~ circuit of Figure 85 to provide the signals
DCSMl, D~'SM2, DCSM3, and DCSM4. These four signal~ actuate
respective drivers 8711, 8712, 8713 and 8714 in Figure 87c
which in turn drive the four poles of step motor 500 as illus-
trated in Figure 87b.
0 The scan clutch 8715 and brake 8716 are illustrated
schematically in the Figure 87d. The mechanical portion of
the scan mechanism comprises a 900 rpm synchronous hysteresis
scan cam motor 8717. The mot~r is~controlled by a permanent
magnet-type clutch~brake assembly, and operates mirror and
~5 lens cams for controlling the positions of the can mirror and
focusing lens in the optical path. The mirror and lens cams
form one assembly which is coupled to the motor 8717 when both
the clutch and brake solenoids 8715 and 8716 are energized,
or is coupled to the main casting through the brake plate when
... 0 . the clutch and brake solenoid are de-energized. When the clutch
and brake solenoids are de-energized permanent magnets in~ure
engagement of the brake plates to the stationary portion of
the assembly and disengagement of the clutch plate from the
moving ~can motor 8717. The clutch~brake ha~ an approximate
'5 electrical energization time of 15 m~ and a de-energization
time of 2 ms. The scan printer speed i8 reduced by a ratio
of 40/125 to obtain the desired angular ~peed for the shaft
of the clutch~brake assembly. Two separate solenoid drivers
72 ~. :
., , . '
9~
1 8718 and 8719 are employed for the clutch solenoid 8715 and brake
solenoid 8716 respectively, but both drivers are actuated by a
common clutch/brake input signal derived as described in
relation to Figure 85.
Solenoid driver 8720 in Figure 87c is employed to
actuate the display mirror solenoid 8721 in Figure 87b. During
an error halt mode (i.e. a manual entry mode) it is desirable to
display any unrecognizable character directly from the document
being read. When an unrecognized character is detected (as
described subse~uently), the system positions the scan mirror in
the optical path to pick up the image of the unrecognizable
character as well as the images of the two adjacent characters.
Solenoid 8721 is then engaged to move a second mirror (see
U.S. Patent 3,872,443, issued November 12, 1974 to John H.
MacNeill, entitled "Visual Display of Unrecognizable Characters
In Optical Character Recognition Machines" and assigned to -
the same assignee as the present application), located
proximate the photo-sensitive array for the characters being
read, to cause the three character images to be displayed -
on the screen for the operator. The operator determines
what the unrecognizable character should be and enters same
through the manually actuated keyboard. The signal which
actuates driver 8720 is designated the CURSOR SHUTTER signal and
is generated in the circuit of Figure 85.
Referring to Figure 87d, the system includes nine light-
sensitive detector assemblies, each including a light emitting
diode (LED-l through LED-9) and nine photo-transistors (Q-l
through Q-9). Eight of these (2 through 9) are identical in
construction, the light-emitting diode and photo-transistor being
.
73
.
.
, . : ,. . ' : . . ' ' '
~4~47
mounted in the same assembly and pointing in the same direction
along parallel paths. These assemblies are then mounted along the
document mechanism, pointed at a prism assembly on the opposite of
the document path. When no document is in the path, light is
emitted by the light-emitting diode and reflected by the prism to
the photo-transistor. Therefore, light crosses the document path
twice when no document blocks a sensing station. When a document
does block a sensing station, the single document effectively
blocks the light twice; that is, the document blocks light emitted
from the light-emitting diode toward the prism, and blocks light
reflected by the prism toward the photo-transistor. This arrange-
ment is very advantageous from an assembly and wiring consideration
and provides a relative large light-to-dark ratio in the photo-
transistor output signal.
The photocell assembly which includes LED-l and photo-
transistor Q-l is employed to sense a window in the driving cam
for the scan mirror. In this case the light-emitting diode LED-l
and photo-transistor Q-l are on opposite sides of the cam.
As illustrated in Figure 87d, light-emitting diodes
LED-l through LED 9 are connected in series between a source of
positive dc voltage and ground. Each of photo-transistors Q-2
through Q-9 are connected to provide appropriate logic signals
to the circuitry in Figure 85 to operate various circuits
illustrated in that Figure. The logic fun~tions effected by
these photo-transistors are described briefly in the following
~ paragraph for ease of ref~rence.
¦ Light-emitting diodes LED-6, LED-7 and LED 8 and photo-transistors Q-6, Q-7 and Q-~ correspond to the three photocell
assemblies 521 proximate the first feed rollers 501 in the
74
:r,~
transport path. These three assemblies are arranged in a line
parallel to the leading or top edge of the document entering the
transport path. They are positioned between the first feed
rollers 501 and read station 520 and are responsible for
detecting skew in a document being entered into the feed path.
Specifically, after the document is picked it is then advanced
; by step motor 500 until it reaches the skew detection station asdetermined by assemblies 521. The document width switch S3 at
the control panel (Fig. 86) permits selection of which skew
station photo sensors are in operation. For very narrow
documents only LED-6 and Q-6 are operative; the other two
assemblies being disabled. For medium width documents LED-7 and
LED-6 and Q-7 and Q-6 are operative. Wide documents utilize
Q-6, Q-8, LED-6 and LED-8.
The skew station photocells perform three essential
functions: detection of the leading edge of the document to
;~ determine the occurrence of picklng failures; testing the
- leading edge of the document for excessive skew; and detection
of the trailing edge of the document in order to generate the
"read complete" signals.
-I Light-emitting diode LED-9 and photo transistor
Q-9 are part of assembly 523 located proximate the second set
I of drive rollers 504 in the transport path. The function of
this assembly is to detect the leading edge of the document
so that solenoid 508 may be actuated and solenoid 506 may be
deactuated. The signal provicled by photo transistor Q-9 is
designated FCBDPC.
Light-emitting diode LED-5 and photo tr~nsistor Q-5
correspond to assembly 525 located just downstream of the first
eject pinch roller 512. When document processing is completed,
the document must be advanced by step motor 500 until the lead-
ing edge of the document reaches assembly 525. When the leading
edge is detected by photo transistor Q-5, the eject solenoids
515, 516 and 517 are energized and solenoid 508 is de-energized.
Photo transistor Q-2 and light-emitting diode LED-2
correspond to assembly 534 at the entrance to the normal
stacker bin 530. Photo transistor Q-3 and light-emitting diode
LED-3 correspond to assembly 536 at the entrance to the reject
stacker bin 531. The signals from these detectors actuate
logic circuitry in Figure 85 which in turn effects the follow-
ing functions: reset the "document in track" flip flop 923, 924
(Figure 9); lnhibit changing of the stacker selector; and
provide an input signal to the "document in reader" lamp.
; 15 The mechanism assembly contains a number of switches
which are automatically actuable during mechanism operation to
monitor and control various functions. These switches are
illustrated in Figure 87d and are described in the following
paragraphs.
The shoe vacuum switch 8724 is a single-pole single-
throw vacuum switch which closes when a document closes the
channels 307 along the underside of feed shoe 30~ to prevent
further aspiration of air by the ~vacuated shoe. Naturally
valve 713 in Figure 7 must be properly positioned so that vacuum
is, in fact, applied to the feed shoe before switch 8724 can
respond to blockage of the feed shoe channels by a document.
Closure of switch 8724 actuate~ the oircuitry in ~igure as to ~e
76
r~ ~.
~9~7
described subsequently.
The feed solenoid switch 322 is a single-pole double-
throw switch which is held actuated (as illustrated in the
Figure 3) when support arm 318 for the feed shoe is at its
normal or raised rest position. When the picker solenoid 320
is energized to lower arm 318 to reach for a document, switch
322 is released. The switch is actuated again when the arm
is raised after a document has been picked. Switch 322 must
then be actuated before the pi ker feed valve 308 can be
actuated to move the feed shoe 304 and document toward the
transport path. Logic for accomplishing these functions in
response to closure of switch 322 is illustrated in Figures
85, 14 and 15 of the accompanying drawings.
; The picker arm forward switch 326 is a single-pole
15 - double-throw switch which is actuated when the picker arm
and feed shoe 304 is in its extreme feed position. Such
-`~ position is indicative that the leading edge of the document
should be engaged by the first set of the pinch rollers in
the transport path; consequently operation of switch 326 is
effected through the circuitry of Figure 85 to operate the
` first feed solenoid 506.
The double document switch 8725 is a single-pole
.. . .
single-throw vacuum switch (referred to in Figure 7) which is
closed when the feed shoe has delivered two or more documents
¦ 25 simultaneously to the transport path. Specifically, switch
¦ 8725 is actuated when sensing port 330 near the leading edge
` of the transport path is blocked, as would occur when the
77
t ,;~ ~,3~
, ' :
bottom of two simultaneously picked documents falls from the
feed shoe as a result of the suction applied to the port 330.
Logic effected by the actuation of switch 8725 is illustrated
in Figure 85.
i
.~ ~
. .
78
. ' ', ',, ' .
III(A.4) MECHANIS~ CONNECTOR soARD
The mechanism connector board schematic is illustrated
in Figure 85 which is subdivided into Figures 85a, 85b, 85c
and 85d. The circuits in these Figures provide direct interface
between the mechanism itself and the controls and logic for
operating the mechanism.
Referring specifically to Figure 85a, NAND gates 8501
through 8509 are provided to operate in accordance with the
state of photo transistors Q-l through Q-9 respectively, of
Figure 87d. Each NAND gate is arranged to provide a binary or
relatively positive output signal when its corresponding
photo transistor is rendered conductive. NAND gates 8507 and
` 8508 also respond to the ND and the MD signals. In this
I regard the MD signal is applied to inverter 8510 before
being applied to NAND gate 8507.
The output signal from NAND gate 8501 is designated
BOL and is utilized in the circuit of Figure 16. This BOL
signal is also inverted by inverter 8511 before being uiilized
in other circuits as indicated in the drawing.
The output signals from NAND gates 8502 and 8503 are
combined in an AND function by applying them together to NAND
gate 8512 and then inverting the output signal from gate 8512
,
be means of inverter 8513. The resulting output signal STG is
a combined indication of the presence or absence of a document
2~ located at the entry to the normal and reject stacker bins
l~ 530 and 531. The status of the picker arm swith 326 is reflected
`I by the state of the picker arm flip ~lop defined by NAND gates
8514 and 8515. The state of the double document switch 8725 is
1,
reflected by the state of inverter 8560. The shoe vacuum switch
8724 and the feed solenoid switch 322 are connected to components
of the circuit in Figure 85d which will be described subsequently.
, 1 80
~, ~,,"p,, ,~
: ' , . ... . ..
' , . ' : ' ' ' ' '
.
III(A.5) MECI~NISM CONTROL LOGIC
Most of the control logic for the mechanism appears
in Figures 9 through 15 of the accompanying drawings and is
functionally interrelated to the manual controls and the master
program counter. The following description is merely a brief
resume of the func-tioning of the logic circuitry, a more de-
tailed description being presented in the section outlining
the master program steps MPS0 through MPS7.
When the system is in the start condition and a
RILN (read line) command signal is received from flip flop
7301, 7302, the master program counter in Figure 15 advances
from MPSO to MPSl. The PAS signal is provided by gate 1304
during the MPSl interval; this signal remains on during the
first 30 ms of the MPS2 interval due to the interaction of the
gates 1303 and 1304. The PAS signal is applied to driver 8702
for the shoe vacuum valve 713, as well as to circuitry in
Figure 85d which generates the PICKER SOL signal to operate
picker solenoid 320. This energization of the picker solenoid
permit: the picker to lower and reach for the document in the
input hopper.
. . 1. ~ ~,
` ~ As illustrated in Figure 85d the input to
il ~
inverter 8517 is connected to vacuum switch 8724 for the feed
shoe. In addition switch 8724 is connected to ~ANI- gate 8518
which drives a one-shot multivibrator 8519. Gates 1404 and
1405 serve to test for closure of vacuum switch 8724 within
¦ ~ four seconds of feed shoe energization. If the switch does
not close within this time the hopper empty flip flop 140~, 1402
l .
is set.
81
i
,
,
~49:~47
As mentioned the circuits in Figure 85d control the
picker mechanism during the MPSl interval. Vacuum switch 8724
for the feed shoe must operate and the solenoid switch 322 must
release to provide proper picker operation. This triggers the
40 ms monostable multivibrator 8519 to delay the release of the
picker solenoid 320 and insure that the vacuum in the feed shoe
has had time to build up and obtain a good grip on the document
being fed. At the end of the 40 ms period of one-shot 8519 the
pickex solenoid is de-energized. When the feed shoe rises,
solenoid switch 322 is reset, allowing the picker feed valve 702
to be energized. The feed shoe moves forward until the picker
arm forward switch 326 is actuated to provide the PAFSM signal
which actuates flip-flop 8514, 8515 in Figure 85a and permits
the master program counter to advance to the MPS2 state.
During the MPS2 interval the flip flop defined by
gates 917 and 918 is set to provide the FFS slgnal to energize
the first feed solenoid 506 via driver 8707. Thirty milliseconds
I after the start of the MPS2 interval the PAS becomes de-energized,
.
~ ~ thereby deactuating shoe vacuum solenoid 713. This also triggers
;; 20 one-shot a519 so that the picker feed val~e 702 is turned off
after 40 ms. This 40 ms interval insures that the vacuum in the
feed shoe has been released so that a document will not be pulled
.
when the picker arm returns to its rest position. Whén the
~ picker arm begins back toward its rest position it releases the
- `~ 25 picker arm forward switch 326, making signal PAF high at the
I' output of gate 8515. This is the signal which~permits the
¦ master program aounter to advance to the MPS3 state.
:1
.,
i 82
' ' :' ~ ', ' ' , , ' ' ' ' ~" ' ' ' ' :
' .
'~ ' ' ,
~IL'Q4a3147
During the MPS3 interval the document is advanced to
the skew sensin~ station. Gates 8401, 8402, 8403, 8404, and
84G5 cooperate to generate the document motor advance pul~e~
-
(DCMT) unti1 either the SKWB or SKER signals go low. The SKWA
5 1 and SKW8 signals are generated in the circuit of Figure 12 in
response to operation of the skew sensor station photocells.
SKWA goes high whenever a document blocks any of the enabled skew
photocells. SKWB goes low whenever the document blocks Q-6 for
narrow documents or all enabléd photo transistors for medium
0 and wide documents. The number of steps of motor 518 required
from the point at which SKWA goes high and SKWB goes low is
a measure of the amount of skew of the top edge of the document.
Gate 8402,and the following circuitry, permits applicaticn of
the DCMT pulses to motor 500 during the MPS3 interval until
.5 siynal SXWB goes low or until the counter 8406, 84~7 detects
a skew error. Gate 8401 enables the counter 8406, 8407 to
count steps from the time SKWA goes high until either SKWB
.
or SKER goes low. If either SKWB or SKER go low, gates 1406
and 1407 operate to permit the master program counter (Figure
~20 15) to advance from the MPS3 state to the MPS4 state~
During the MPS4 interval, te-~ts are made to determine
if a document is left in the track from a previous operation
~` and if the scan m~rror has returned to it~ BOL (beginning of
~ line) position. A test is also made to determine if the docu-
`25 ment advance counter 8406, 8407 has detected a skew error. The
tests are performed in the circuit of Figure 14. Specifically,
NAND gate 1408 responds to a detected skew error by setting the
flip flop defined by gates 1409 and 1410. In most operations,
83
,
:--- - . '. " '
' ~ ~ ' '' . '''':'
~,7
setting of the flip 10p 1409, 1410 actuateq NAND gate 1411 which
in turn operates circuitry in Figure 21 to provide the reject
command (REJCM) signal. The system is in the MPS4 state f~r only
a few microseconds to make these tests and then advances to the
MPSS state. If, in the MPS5 state, the reject co~nmand and the
read complete signals are not present, the system proceeds to
perform a load format or read operation by enabling the respective
load format or read program counter.
If either the read complete or reject command signals
are present during an MPS5 interval, the system automatically
advances to the MPS6 state. The document must be advanced to
the eject enter station during MPS6 if it has not already been
advanced that far during the MPS5 interval. NAND gate 1305
generates the signal to effect this operation, this signal
being applied to gate 8403. Gate 8403 responds by generating
advance pulses DCMT for motor 500 until the top edge of the
~- document blocks the eject photo transistor Q-5. Gate 1411
enables the advance of the master program counter from MPS6
to MPS7 when the ejected document en~ers a stacker throat.
i Gate 1411 requires that the EJEN signal be high, that any
data output sequence be complete (as indicated by the OUT-IN-PRO
signal) and that there be no document~ in the stacker throat
~as indicated by the STG signal).
.
At MPS7 the flip flop defined by gates 919 and 920
is reset. This flip flop controls the second feed solenoid 508.
When flip-flop 919, 920 was set, signal SFS was low and
set flip-flop 1101, 1102 in Figure 11. When flip-flop 1101,
. ,
1102 is set and signal SFS becomes high, g~te 1103 generætes
84
, . . ... . . . . . .
.. . . . .. . . . .
~ 4~
the F~S signal to actuate the eject solenoids 516, 517 and 518.
When a document bl.ocks the entrance to the stacker section of
the mechanism, thereby blocking photo transistor Q-4, the STEN
signal goes low to reset flip flop 1101, 1102 and deactuate the
eject solenoids 516, 517 and 518.
Return of the master program counter from the MPS7
state to the MPS0 state is effected by the gate 1412 after the
trailing edge of the document has passed the skew sensing stationO
'`
:
~ . .
!-
.
' ' ;
,. : :
~ :
!
:85
47
I I I (A . 6 ) MASTER PROGiRAM COUNTER
The master program counter circuit is illustrated in
Figure 15. The circuits which implement the logic necessary
to increment the master program counter are illustrated in Fig.
14. Detailed description of the master program counter is
provided in the form of an outline wherein each step in
the program sequence and the implementing circuits are identi-
fied. The following two paragraphs serve as introduction to
the outline by describing certain general operation.
A program advance or step is initiated by a low signal
on one of the inputs to gate 1413. The output of this gate is
applied to NAND gate 1414. Two inputs to gate 1414 from gates
1415 and 1416 are single-cycle control signals used during
debugging operations; these are always high during normal
operation. Gate 1414 samples the advance signal at TPE time to
set flip-flop 1417, 1418. With this flip-flop set, its output
` is sampled at TPF time by gate 1419 and inverter 1420 to
generate MPCT and MPCT pulses. The MPCT (Master Program Counter
Toggle) pulses go to the thrée bit master program counter formed
by flip-flops 1501, 1502 and 1503. The outputs of this counter
go through gates 1504, 1505, and 1506 to a three-bit to eight-
output decoder 1507. Gates 1504, 1505, and 1506 are used during
a read test mode to force a count of 5 into the decoder. Flip-
-
flop 1417, 1418 is reset by TPA.
The MPCT signal sets flip-flop 1508, 1509 which 19 also
reset by TPA. The output of gate 1508 goes to the "D" input
. , ,
l of the decoder 1407 which has the effect of disabling the
.
.
86
47
decoder fro~ th~ beginning of MPCT (TPF) to the beginning of
the next T~. The counter advances at the trailing edge of ,
MPCT. wi~h the decoder disabled during this short period, it
canno~ generate any spurious pulse while the counter advances.
en the decoder is thusly disabled, all inputs to gate 1413 are
hlgh. When the decoder is enabled lt pxoceeds to the next step,
ena~lin~ another input gate for gate 1413. Another low slgnal
input to gate 1~13 cannot occur until the appropriate conditions
are present as set forth in the master program outline. A hopper
empty (}~E) or document error (DCERR) condition cause the counter
to immediately return to state MPS0 through gates 1510 and 1511.
The remaining c1rcuits in Figu~e 14 are used to detect various
faul~ conditions such as Hopper Empty, PicX Fail, Document Jam,
Do~b~e Document, and Skew Error.
In the outline for the master program, which is
' " ' .
- presented in the following section, the re~erenced program
steps occur in during the master program counts indicated in
the following table:
MP Count Proqram Steps
~20 MPS0 Al - A3
~ MPSl A4 - A15
:~
~PS2 A16 - A25
,
MPS3 A26 - A29
MPS4 A30 - A35
MPS5 A36 - A44
MPS6 A45 - A51
MPS7 A52 - A53
, ' ' .
87
... . .
.
, . ....... .....
.7
III(A.7) MASTER PROGRAM OPERATIONAL OUTLINE
Al. Detect for read line or transport test commands (gate 1421).
If present, proceed to A2; if not, remain in standby.
A2 Detect lf mechanism is in start position (gate 1422). If
yes, proceed to A3; if not, return to Al.
A3. Check for document in skew sensor station (no document if
SKWA is high gate 1422). If no document, proceed to A4;
if document present, return to Al.
A4. Energize picker arm solenoid 320 (gates 1303, 1304) and
shoe vacuum solenoid (gates 8520, 8521, 8522, and 8523).
Proceed to A5.
A5. Detect if shoe vacuum switch 8724 is closed (gate 1405).
If not, proceed to A6; if yes, procead to A8.
A6. Detect if 4.0 second timer expired (counter 1001, 1002,
1003; gate 1404). If not, return to A5; if yes, proceed
to A7.
A7. Set the hopper empty flip flop (1401, 1402), reset the
start flîp flop 903 (gate 902), and return to Al.
, A8. Detect if picker arm solenoid switch 322 is released (is
',20 arm down?) (gates 8524, 8525, 8526). If yes, proceed to
1
- A9; if not, proceed to A14.
A9. De-energize picker arm solenoid 320 (gates 85?1, 8522, and
8523). Proceed to A10.
A10. Detect if picker arm solenoid switch 322 is actuated (is
~25 arm up?) (gates 8524, 8525). If not, proceed to A14; if
yes, proceed to All.
All Energize picker feed valve 702 (inverter 8527, flip flop
8528 and NAND gate 8529). Proceed to A12.
.
88
~ , ' . .
'.
, ' ' '
9~
A12 After picker arm start switch is released, energize valve
713 to permit detection of double document feed. Proceed
to A13.
A13 Detect if the picker arm forward switch 326 is actuated;
if not, proceed to A14 if yes, proceed to A16
A14. Detect if the 4.0 second timer expired (counter 1001, 1002,
1003; inverter 1423, gate 1424). If yes, proceed to A15;
if not, return to A4.
Al5. Set pick failure flip flop 1425, 1426 and reset start flip
flop 903 (gates 1403, 901). Proceed to Al.
A16. ~nergize first feed solenoid (gates 917, 918), start 30 ms
delay (counters 830, 831; flip flop 1004~, and deactuate
shoe vacuum valve 713 (gates 1303, 1304). During 30 ms
delay proceed to A17 to detect double document feed; after
delay, if no double document feed is detected, proceed to
A21.
A17 Detect for closure of double document vacuum switch 8725
(gates 1427, 1409, 1410). If closed, proceed to A18; if
not, proceed to A24
A18 Detect if system is in transport test, load format, or
not reject modes (gates 1428, 1429). If so, proceed to
.,
A19; if not, proceed to A20.
A19, Actuate document error signal (gate 1403) and reset start
flip flop 903 (gate 902). Proceed to Al,
A20. Set the document reject signal (gates 1428, 1430, 1431,
2102, 2103). Proceed to A26
i A21 Detect if shoe vacuum switch 8724 is deactuated (gate 8518). If not, proceed to A24: if de-actu~ted, proceed to A22.
89
..~
1~4~7
A22. S~art 40 ms delay (gate 8530, one-shot 8519). At end of
delay deactuate picker feed valve 702 (flip flop 8528,
gate 85~9). Proceed to A23.
A23. Detect if the picker arm forward switch 326 is released
(gate 1432). If released, proceed to A26; if not, proceed
to A24
A24 Detect if 1.0 second timer has expired (fl.ip flop 1005;
gates 1433, 1434). If not, return to A16; if so, proceed
to A25
A25 Set the pick failure flip flop 1425, 1426 (gate 1434) and
reset start flip flop 903 (gates 1403, 902). Return to
Al.
A26 With the first feed solenoid 506 still energized, actuate
document advance motor 500 a sufficient number of steps
until either SKWB or SKER goes low; count motoE steps
between SKWA and SKWB signals (flip flop 917, 918; gates
8401, 8408, 8409, 8410, 8403, 8404, 8405; counters 8406,
8407). Proceed to A27
A27 Is either SKWB or SKER low? (Gates 1406, 1407) If so,
proceed to A30; if not, proceed to A28.
A28. Detect if 250 ms timer has expired (flip flop 1006; gate
1435). If not, return to A26; if so, proceed to A29.
~ ~ A29. Set document error signal (gates 1435, 1425, 1426) and
: reset start flip flop 903 (gates 1403, 902). Return to Al,
: 25 A30, Detect if SKER is low, indicating a skew error (gates
1408, 1409, 1410). If so, proceed to A31; if not, proceed
to A330
A31. Detect if unit is in either of thF transport test, load
format or not reject modes (gates 1428, 1430). If so,
, , .'. ' ,' ' '~
,'', '.',' '' ,' ' , ' ~ ', ' . , ' ' ', ' ':' ', ' ''" ' ".' ' ' .' ' .'' ", , ' , , ' ,' . , ', .: ' ' '
proceed to A35; if not, proceed to A32.
A32. Set document reject signal (gate 1431). Proceed to A33.
A33. Determine if the previous document is in the track, or if a
transport test mode exists, or if the BOL signal is high (gates
1436,1437). If so, proceed to A34; if not, proceed to A36.
A34. Determine if the 1.0 second timer has expired (gates 1433,
1438). If not, return to A30, if so, proceed to A35.
A35 Set document error signal (gates 1438, 1439, 1440, 1429)
and reset start flip flop 903 (gates 1403, 902). Return
to A1
A36, Detect if unit is in transport mode and signal SKWA is
high (gate 1441). If so, proceed to A44; if not, proceed
to A37,
A37. Detect if document reject condition exists (gate 1442).
If so, proceed to A44; if not, proceed to A38.
.~ A38 Detect if load format mode is in effect (decoders 2301,
: 2401, input signals LDFT and LDFT). If so, proceed to
~: A40; if not, proceed to A39.
A39, Read document in accordance with steps in the read program
(refer to description of read program steps). Proceed to
... , ~ :
~: : A4:3.
:~ A40. Process conditioning document in accordance with format pro-
gram~steps (refer to description of format steps). Proceed
tc~A41.
~25 A41. Determine if a format error occurred (gates 2001, 2002,
4301, 45Dl, 5101,~5102,~5103). If not, proceed to A43;
if so, proceed to A42~
.~ 91
, ir~ r~'
. . .
' ~
A42 set the format error flip flop 2104, 2105 and reset the
start flip flop 903 (gates 2101, 902). Proceed to A44,
A43 Deter~ine if the read operation or format entry operation
has been completed (decoder 2401; flip flop 2106, 2107;
gates 1442, 1443). If not, return to A36; if so, proceed
to A44
A44. Determine if all the read data has been transferred out
of the system and if the read and format program counters
are at zero (gates 1444, 1443, 2501). If not, return to
A36, if so, proceed to A45,
A45 End of document sequence; advance document until leading
edge covers eject entrance photocell assembly 525 (gate
7303; flip flop 7304, 7305t gate 7306 flip flop 7307,
7308; gate 7309; inverter 7310 gates 1305, 8403, 8404,
8405). Proceed to A46.
; A4h. Determine lf document has reached the eject entrance
photocell 525 (gate 1411, signal E3EN). If not, proceed
to A49; if so, proceed ~o A47.
A47. Determine if previous document iY jamming entrance to
~ 20 stacker section as determined by photocell assembly 527
:~1 (gate 1411, signal STG). ~ so, pro~eed ~o ~49 if not,
:~a~ :
~3. proceed to A48,
~j . ' ' '
.~ : A48. Determine if all data has been tr~n-f~rred~out and the
~i~ end of document sequence is complete ~gate 1411, signals
OUT-IN-PRO and MPS6). If not, xeturn to:A45 if 80,
proceed~to~A51. ~ -
A49~ Determine if the~l.0 second timer has expired (gates 1433,
1445). If not, return to A45; if~so,~proceed to A50.
. 1', .
iii 92
.'~ ' , .
' ' ' ' ,
.,
17
A50. Set document jam fllp flop 1439, 1440 (gate 1445) and reset
start flip flop 903 (gates 1403, 902). Return to Al.
A51. Deactivate second feed solenoid 508 (gate 921; flip flop
919, 920) and activate eject solenoids 515, 516, and 517
(flip flop 1101, 1102; gate 1103). Proceed to A52.
A52. Determine if signal SKWA is.low, indicating that the docu-
ment is out of the skew sensor station (gate 1412). If so,
return to Al; if not, proceed to A53.
A53. Determine if the 1.0 second timer has expired (gates 1433,
1446). If not, return to A51; if so, return to A50,
'
1 93
:
47
1 III(A.8) RFAD AND FO~MAT PRO~,RAM COUNTER
The read and format program counter and related
circuits are illustrated primarily in Figures 17 through
25 of the accompanying drawings, however circuits in other
figures are of course related insofar as they may provide
or receive signals related to the read and format program
counter operation. Complete description of read and format
program counter operation is provided in the format program
counter outline and read program counter outline included
. .
; 10 herein below. The following general comments are included
to facilitate an understanding of these outlines.
The read and format programs have t:heir individual
control gates but share the same 4-bit counter and its
control. These controls operate similarly to those associated
with the master program counter with one exception: the
master program counter only advances in sequence or is reset
to zero; the read and format programs not only advance in
, sequence under some conditions but are also steered or
jumped to other counts according to conditions detected by
the control circuits.
Gates 1601 through 1606 and 1608 through 1619
are the gates which con-trol the read program counter to
step in sequence from one count to the next. The signals
are OR'd together by the 8 input gate 1607. Gates 2003
through 2019 are the gates which con-trol the format program
counter to step in sequence from one count to the next. The
signals from these gates are OR'~d by gate 2020 which, when
actuated, provides a low FPCA signal. This signal is also
OR'd at gate 1607. Gates 2502 through 2518 are the
gates whic~ control the steering or jump
.' , .
:
~,, ~ ' .
.' '' .
.~ , . . .
: ' '. . , . ' ' . . . . .
conditions for the read and format programs. Any condition
which calls for a jump in the program will generate a low input
signal to ~ate 2519 which enables flip flop ~520 to become set
on the positive-going edge of the next TPD pulse. The Q output
signal from the flip flop 2520 is designated JPCT and is applied
as one input signal to gate 1607. Since gate 1607 thus receives
input signals for controlling read program stepping, format
program stepping, and all program jumps, this gate controls all
advances of the program counter whether sequentially or not.
Gates 2521 through 2524 are utili~ed to generate the
step number to which a program jump is to be made and receive
appropriate signals from gates 2514, 2516, 2517 and 2518. The
jump control signals which are not connected to gates 2521
through 2524 are utilized to jump the program counter to zero
(RPS0 or FPS0). When signal ~PCT is high and TPD is high, gate
2525 strobes the jump count into the 4-bit memory circuit 2526.
The output signals from memory circuits 2526 are applied to
the preset inputs of the 4 bit binary counter 2527. The JPCT
; signal is also applied to the load signal of counter 2527.
Counter advance pulse RPCT is generated at gate 16260
If signal JPCT is high, counter 2527 ad~ances once for each
RPCT pulse. If JPCT is low, counter 2527 is preset to the jump
count stored in memory circuit 2526, It will be noted that the
RPCT signal is generated in a manner similar to the MPCT.
; 25 The read program decoder 2301 and associated output
- inverters are illustrated in Figure 23; the format program
decodér and associated output inverters are illustrated in
Figure 24. These ~re four-bit to sixteen-output decoders.
~r,r r
:
Decoder 2301 is enabled when signal LDFT is low, as is the case
during read mode operation. Decoder 2401 is enabled when signal
LDFT is low, as is the case in the load format mode. Signal
DCIN, applied to both decoders, is high during the short time
interval when the program counter is changing state. This inhibits
any spurious pulses from heing generated by the decoder when the
counter is changing state.
96
~r~
III(A.9) FORMAT PROGR~M
The format program has sixteen discrete steps corres-
ponding to the sixteen counts in counter 2527 and as decoded by
decoder 2401. These steps are listed below with a brief notation
as to -the functlon performed when each step is active.
FPSl Move scan to vertical format mark position.
FPS2 Advance document one step and count.
FPS3 Test for end of document or if number of lines exceeds
maximum.
FPS4 Perform line position analysis.
FPS5 Test results of line position analysis.
FPS6 Memory write cycle for document advance counter.
FPS7 Reset document advance counter and initiate horizontal
format mode.
FPS8 Scan for horizontal format and store horizontal format
data.
FPS9 Advance document twelve steps and count.
FPS10 Test for signal DAT177 (advance document 128 steps).
FPSll Memory write cycle for DAT177.
FPS12 Reset document advance counter to zero.
FPS13 Reset document advance counter to zero; memory write
cycle; end of document.
FPS14 Set read complete flip flop.
FPS15 Reset format advance counter
.,
97
1 III(A.10) FORMAT PROGRAM OUTLINE
BL(FPSO) Determine if proper conditions exist to initiate
format program (gates 1704, 2005, 202, 1607)~
Reset document advance counter 8406, 8407 (gates
2501, 2526, 2527, 8414). Proceed to B3 ~gates
1607, 1625, 1627, 1628, 1626 and counter 2527).
B2 (FPSl) Determine if the scan mirror is directed toward
the left edge of the document bv sensing whether
or not photo transistor ~-1 has been activated
(gate 2006). Proceed to B3 (gates 2010, 2020,
1607, 1625, 1627, 1626, and counter 2527).
B3(FPS2) Advance document one step and add one count to
document advance counter 8406, 8407 (gates 8415, ~ -~
8408, 8409, 8410, 8403, 8404, 8405). Proceed to
B4 (gates 2007, 2010, 2020, 1607, 1625, 1627,
1626, counter 2527). ~-
; B4(FPS3) Determine if the end of the document has passed
the skew sensor station or if 96 vertical format
words have been placed into memory (gates 2018,
2001). If the end of document has no-t passed
the skew station and86 vertical format words
have not been placed into memory, proceed to B5
(gates 2018, 2019, 2020, 1607 etc.). If the end
of document has not passed the skew station but 86
~ vertical format words have been placed into membory,
- set the format error flip-flop and the read complete
flip-flop and reset the start flip-flop and return
to Bl (ga-tes 2001, 2104, 2105, 2109, 2110, 2102,
2103, 2506, 2509, 2519). If the end of document has
passed the skew sensor station proceed to B14 (gates
2025, 2517, 2519; flip-flop 2520; and gates 2521,
2523, and 2524). Clear the line position
.
98
.
.. . . ~ . . .
-: .
.. . . .
1 analysis circuits 6623 through 6608 (gate 6602).
B4(FPS4) Perform line position analysis (refer to line
position analysis section). Upon completion of
line position analysis proceed to B6 (gates 2009,
2010, 2020, 1607, etc.).
B6(FPS5) Examine results of line position analysis. If
mark is centered proceed to B7 (gates 2012, 2014,
2020, 1607, etc.). If no mark is detected proceed
to Bll (gates 2024, 2518, 2519, 2522, 2524; flip-
~ flop 2520). If a non-centered mark is detected,
set the format error flip-flop and the read comp-
lete flip-flop, reset the start flip-flop. and
return to Bl (gates 2002, 2104, 2105, 2109, 2110,
2102, 2103, 2506, 2509, and 2519).
B7(FPS6) Store the document advance count, if not equal to
zero, with flag DAC8 (DAT177) = 1 (gates 2003,
2004, 6306, 6307; multiplexers 2601 through 2605;
gates 6003, 6004, 6311, 6312; multiplexers 4801
through 4804) by selecting DACl through DAC7 as the
data input and the vertical format address count
as the memory address. Increment the vertical
format address counter 5201, 5202 (gates 6018,
6019). Upon completion of the memory cycle proceed
to B8.
B8(FPS7) Reset document advance counter 8406, 8407 (gates
2527, 8414). Reset scan advance counter 2801-2803
(gates 3601, 3602). When scan mirror returns to
beginning of line, proceed to B9 (gates 2013, 2014,
2020, 1607, etc.).
.
':
.. 99
. . . , - , , . -. . ..
~ ' " ' ' , ' . ... .
B9(FPS8) Determine that a vertical format mode with no horizontal
format exists and that there is no reject command and
the scan mirror is at the beginning of the line. If
these conditions obtain proceed to B10 (gates 2017,
2016, 2015, 2014, 2020, 1607, etc.). If horizontal
format mode exists, scan the line to detect field
definition marks; for each mark detected store the
scan count and the lowest order bits of the character
recognized in the horizontal forma-t memory; advance
the horizontal ~ormat memcry address counter (multi-
plexers 2601-2605, gates 3001-3003, multiplexers 4801-
4804; and memory controls section in general). Test
for excess number of horizontal field and set format
error (counters 5104, 5105; gates 5101, 5103, 2104,
2105, 2109, 2110, 2102); test for unrecognized field
characters and set format error (gates 5102, 5103,
2104, 2105, 2109, 2110, 2102), enter the horizontal
~ format data into the memory (refer to memory section
`~ - for description); if format error is detected return
~20 to Bl (gates 2506, 2509, 2519)~ At the end of the
line scan proceed to B10 (gates 2017, 2016, 2015, 2014,
~ 2020, 1607, etc.).
! ~
BlO(FPS9) ~dvance document six steps for six-lines-per-inch pitch
or twelve steps for three-lines-per-inch pitch (gates
8416, 8415, 8403, 840A, 8405); increment the document
advance counter 8406, 8407 (gates 8416, 8415, 8408,
8409, 8410); return to B2 after appropriate number of
, ~ steps have been implemented (gates 2021, 2023, and
2519)~ Test for even number of horizontal format words
~,
"'' 100
~L~)4!~147
stored; i~ number of words is not correct set reject
command and return to Bl (gates 4501, 5103, 2104,
2105, 2109, 2110, 2102, 2506, 2509, and 2519).
Bll(FPS10) Determine if count in document ad~ance counter
1 8406, 8407 has reached 127 steps (gate 8411). If
not, return to B2 (gates 2022, 2023, 2519); if so,
proceed to B12 (gates 2008, 2010, 2020, 1607, etc.).
B12(FPS11) Identical to B7 except that exit is to B13 instead
of B8.
B13(~PS12) Reset document advance counter 8406, 8407, to zero
(gates 2527, 8414). Return to B2 (gates 2023, 2519).
B14(FPS13) Reset document advance counter to zero (as in B13).
Proceed as in step B6 except to exit to B15.
~ B15(FPS14) Set read complete flip flop 2106, 2107. Proceed to
i B16 (gates 2019, 2020, 1607, etc.).
Bi6~(FPS15j No functions. Proceed to B1 (gates 2019, 2020, 1607,
etc.).
: ' '' ' ' . '
'
'` ' :
`, '~ . , ' ' ' ' '
;'~ . ' '
.
' . ' " ', ~
` , ' ~.
: ~ .
101 ' :
':
~: ~ , . . . , . - . . .
. . ,, . ~, ., ~ , " , . . ;:
III(A.ll) READ PROGRAM OUTLINE
Cl~RPS0) Determine if proper conditions exist to initiate read
program (gates 1704, 1601, 1607). Reset document
advance counter 8406, 8407 (gates 2501, 2526, 2527,
8414). Proceed to C2 (gates 1607, 1625, 1627, 1628,
1626, and counter 2527).
C2(RPSl) Fetch vertical format document advance number from
memory (gates 4307, 4308, 4309, 6001, and associated
memory cycle controls). Gate the ones complement of
the fetched number into the document advance counter
8406, 8407 (inverter 8420; gates 8419, 8410, 8421-
8427). Increment vertical format address counter
5201, 5202 (gates 6018, 6019). Store contents of
horizontal format address counter 5104, 5105 in
memory latches 5106, 5107 (inverter 5112). Store bit
8 of the addressed memory word in flip flop 1702,
1703 (gates 4701, 1701). At the end of the memory
cycle proceed to step C3 (gates 4307, 4308, 4309,
1602,~1606, 1607, 1625, 1627, 1628, 1626).
C3~RPS2) Examine contents of document advance aounter 8406,
- 8407 (gate 8411). If original number was all zeros
(i.e. DAT177 is low), set read complete flip flop
; 2106, 2107 (gate 2502) and return to Cl (gates 2505,
2519;~flip flop 2520); if original nu~ber was not
:
all~zeros (l.e. DAT177 is high), proceed to C4 (gates
1603, 1606, 1607, etc.).
.,
',~ ' ` :
'`
102
~71 4 7
C4(RPS3) Advance document until signal DAT177 goes low (gates
8428, 8415, 8408, 8409, 8410, 8403, 8404, 8405).
Examine condition of flip flop 1702, 1703. If signal
DAF8 is high when DAT177 is high, there is no line
to read, obtain advance increment from memory and
return to Cl (gates 2508, 2509, 2519, etc.). If signal
DAF8 is high and DAT177 is high, read the line by
proceeding to C5 (gates 1614, 1619, 1607, etc.).
C5(RPS4) When the read complete flip flop 2106, 2107 has been
set, return to Cl (gates 2503, 2505, 2519, etc.).
If the reading of a line has not been completed, and
if there is no output of data in process, but the
command to read i5 still present, preset counter 1713,
1714 (gate 1712) and proceed to C6 (gates 1615, 1619,
1607, etc.).
C6(RPS5) Gate the horizontal format address from latches 51Q6,
~; 5107 to the horizontal address counter 5104, 5105
(gates 5108, 5109, 5110; inverter 5Ill). Reset the
scan counter 2801, 2802, 2803 (gates 3601, 3602).
Proceed to C7 when the beginning of a line photocell
.
assembly (photo-transistor Ql) is actuated (gates
1608, 1605, 1606, 1607, etcO).
C7(RPS6) Read the line a~ the read station by performing the
folIowing functions:
25- a) at the beglnning of the RPS6 step, preset the
data address counter 5001, 5002, to a count
of 44 (to be converted to a count of 88 by the
1 .
~ I
l 103
memory address multiplexer) (gate 1901, inverter
1902, gate 5003, inverter 5006, flip flop 5007,
gates 5008, 5009, inverter 5010, gates 5011, 5012).
~ b) enable scan mirror clutch/brake 8715, 8716 (gates
~ 3802, 3803, 3703, 3?04, 3705).
c) count scan slices at counter 2801, 2802, 2803 (gates
3703, 3701) and generate the scan duration ~ignal
SCDR (3807).
d) write the data and the scan count into the memory
data section (gates 5601, 5602, 5603; flip flop
`~ 5604; and memory control circuitry).
e) detect and remember location of unrecogniæed
characters (gate 5701; flip flop 5702, 5703).
f) perform line position analysis (refere~ce description
lS of line position analysis circuits).
g) if operating in vertical format mode, gate signal
~ . . . . - .
SCDR to provide the read enable signal RDEN for
each character slice (gates 4317, 4316).
h) Generate the LINE COMP signal at the data address
counter 5001, 5002 when the counter is full.
, ,
:~ .i) Proceed to C8 when the entire line has been read
(gates 1616, 1619, 1607, etc.).
: C8(RP57) The line~position analysis results in the generation
.,:
of signals indicating that She character sensing array
- i filled, as well as pulses (~NAT) for initia~ing ::
.
. movement of the document during fine line adjust,
.
, and pulses ~AC) to indicate that the ~ine line :
:. -, ' ,
. . 10
~' ' .
..
~1~49~
adjus-tment operation has been completed. ~eneration
of these signals is described in the section dealing
with line position analysis. If the array has been
filled and a reject mode established, set the reject
command and return to Cl (gates 1707, 2111, 2109,
2110, 2102 and inverter 2103; gates 2506, 2509, 2519,
etc.). If the array has been filled and no reject
mode has been established, proceed to C15 (gates 1707,
2516, 2517, 2519, 2521 through 2524, etc.). Determine
if the fine line adjust procedure has been completed
without the array having been filled (gate 1706): if
there is no read error set the buffer full flip flop
5505 and return to Cl (gates 2529, 2530, 2504, 2505,
2519, etc.); if there is a read error after one attempt
`15 to recognize the previously unrecognized character
(LTRY = 1), return to C6 (gates 2513, 2514, 2519, 2521
i: :
.~
through 2524); if there has been a read error and
the second try at recognition has been completed (LTRY = 1~"
; proceed to C9 (gates 1617, 1607, etc.). Increment
counter 1713, 1714, at the end of the RPS7 interval.
C9(RPS8) Reset the horizontal ~can counter 2801 through 2803
(gates 3601, 3602). When the scan returns to the
, .
beginning of the line proceed to C10 (gates 1608, 1605,
1606, 1607, etc.).
~ 25~ ClO(RPS9) Scan the line as many as four times if all characters,.,~,
~ are not recognized. Re-read only those characters
i~ :
~ ~ not recognized during the RPS6 step.
.
i l~
105
~.
' ~ ~' ` ` ' ' , ,' ` `~ '
: ' ; '
' ! .f.,~
9L7
a) Indicate the number of the current scan (gate
17lS, counter 1713, 1714; gate 1716; inverter
1717~.
b) Adjust photocell detection level in accordance
with the number of re-scans (gates 1718-1721).
If all the characters have been recognized or
the E~R FLD signal is high, ~et the buffer
full flip flop 5505 (gates 570~, 5702, 5703,
5502, 5503) and return to Cl (gates 1801, 1802,
2510, 2512, 2519, etc.).
d) If the ERR FLD signal is still high, and it is
; not the fourth scan of the line, return to C9
, (gates 2515, 2517, 2519, etc.).
~ ,, ..... :
e) If the ERR FLD signal is~still high, and the
15~ ~ last re-scan attempt has been made, and a reject
mode exists,set the reject flip ~lop 2109, 2110
' and return to Cl (gates 1705, 2112, 2506, 2509,
2519, etc.).
f) If the ERR FLD signal is high, and the last re-scan
has been attempted, and an error halt mode exists,
proceed to Cll (gates 1705, 1604, 1606, 1607, etc.).
~ - .
g) If the ERR FLD signal is still 1, and the last
re-scan has been attempted, and ~an error substi~ute
mode has been initiated, set the bu~fer full flip
flop (gates 5501, 5503) and return to Cl (gates
2507, 2509, 2519, etc.).
.
:
.,
106
.j .. . I
~L~45~7
Cll(RPS10) Reduce scan motor drive to half speed in preparation
for pointing to unrecognized character (gates 2531,
2532, 806, flip flop 805; counter 829; flip flop 836).
When the scan mirror returns to the beginning of the
line, proceed to C12 (gates 1608, 1605, 1606, 1607,
etc.).
C12(RPSll) Search for first unrecognized character in memory and
place horizontal count of that character in the
EPR register 2704-2706 (reference description in
section on memory controls). Reset the horizontal
scan counter 2801, 2802 (gate 3602). If all
characters in the line are recognized, reset flip flop
5702, 5703 to drive the ERR FLD signal high (gate 5705).
When the ERR FLD signal goes high, return to Cl (gates
2511, 2512, 2519, etc.). If the ERR FLD signal remains
low, proceed to C13 (gates 1618, 1607,-etc.).
; C13(RPS12) Enable the scan mirror clutch/brake 8715, 8716 (gates
3702, 3703, 3704, 3705). ~dvance mirror to cursor
position (CRPS); allow for clutch~rake stop time
by modifying the scan count to cause deacutation of
! the clutch/brake prior to reachiny the cursor position
(gate 3701; counter 2~301-2803; adders 4001-4003;
data registers 2704-2706; gates 3315 through 3828,
3302; inverter 3329). Upon reaching the cursor position
proceed to C14 (gates 1609, 1613, 1607, etc.).
C14(RPS13) System in pause condition to permit manual entry of
unrecognized character from keyboard; repeat reading
107
,
of line; reject document; clear keyboard to enter
complete line.
a) Enter character via the keyboard and return to
Cll (flip flops 6202, 6204; gates 6203, 6205;
flip flop 4502, 4503; gate 4504; gates 2518,
2519, 2521-2524, etc.).
b) Repeat reading of line and return to C6 ~gates
8325-8329; inverter 8330; gates 2514~ 2519,
2521 through 2524, etc.).
c) Enter complete line, clear the keyboard and
proceed to C15 (inverter 8010; gates 1610,
1613, 1607, etc.~.
d) Manual reject of document b~ operator and return
to Cl (inverter 8331; inverter 2113; gates 2114,
~' 15 2115, 2109, 2110, 2102, 2506, 2509, 2519, ~t~.).
C15(RPS14) Return mirror and cam to beglnning of line (gates 3706,
3705). Upon reaching beginning of line proceed to
C16 (gates 1608~ 1605, 1606, 1607, etc,).
C16(RP515) System is paused for operator intervention in the form
1~ 20 1 of entry of a complete line, r~peat of a line~ or
¦~ manual reject:
;¦' a) Enter unrecognized character through keyboard
`~ (flip flops 6202, 6204; gates 6203, 6205, flip
~ flip 4502, 4503; gate 4505~.
¦ 25 b) Enter characters to fill memory, set buffer full
flip flop, and return to Cl (gat~s 6320-6323,
1610, 1613, 1607, etc.)O
., ~ .
I .
~1 108
,.~. ,. _
~L~4~ 7
c) Repeat line and return to C6 (gates 8325 through
8329; inverter 8330; gates 2514, 2519, 2521-2524,
etc.).
d) Manual document reject and return to Cl (inverter
8331, gates 2116, 2113, 2114, 2115, 2109, 2110,
2102, 2506, 2509, 2519, etc.).
,
,'" ~ ~ ' ' '
~4~.7
.
III(A,ll) MEMORY
III(A.ll.a) GENE~AL
The memory con~ists of 512 12-bit words and is,construct
ed using 256 x 1 semiconductor static random access chips with
5~ 8-bit address decoders; chip-select ~C/S) and read-write command
(R~W) input siynals are utilized.
~igure 64 illustrates a memory module containing twenty-
four each INTEL Model 1101 memory chips. There are twelve data
in~t lines (MD~-l through 12) and twenty-four data output lines
(MDO-I through 12, and MDO-l through 12). Eight memory address
line~ MAD-l through 8) select the 256 word positions of each
chip. C/S-l selects memory addresses O - 255; and C/S-2 selects
memory addresses 256-511. When the write line R~W is high, the
data on the data input lines MDI-l throuqh 12 is written into the
' 15 memory position specified by address MAD-l through 8 and C/S-l,
: C/S-2, Data ou~put appears on lines MDO-l through 12 correspond-ing to the contents of the position specified by address MAD-l
through 8 and C/S-l and C/S-2. Driver circuits for the data
: output signals are illustrated in Figure 65.
. 20 III ~Aoll~b) READ-WRITE
- There are memory cycle~ which are referred to as
Read Only and Write~Read, The latter are controlled primarily
. .
by making the RfW line high at the correct time in relation to
.. , .. ~ ,
the data and address inputs. A read only cycle requires only
the correct addressing of the memory.
III(A.ll.c) SINGLE-DOUBLE CYCLE
There are also memory sequences which are ref~rred
to as Ringle-cycle and double-cycle. In the ~ingle-cycle
',
1110
,.: , ' ' , .' ,:
~4~47
sequence a single data word is writtn into or read out of a
specifled address. In the double-cycle sequence two data words
; are written into or read out of two successive addresses.
III(A.ll.d) MEMORY PARTITION
The memory is partitioned into three basic data areas.
Area one consists of 256 words selected by C/S~l being
low. This is the area allocated to the horizontal format infor-
mation. Each field to be specified requires a beginning and end
point, which are specified by the corresponding scan count
stored in this portion of the memory. The 256 words are suffi~
cient to specify a total of 128 fields on a document.
Area two consists of 86 (0-85) words selected by
` C/S-2 being low. This is the area allocated to the vertical
format information. Therefore the maximum number of incremental
advances from the top edge of the document to the first line to
be read and to each succeeding line is 86. The maximum length
document is 14 inches and the maximum number of lines per inch
` is 6; therefore 84 or 85 is the maximum number of memory words
required for vertical format.
Area three consists of 168 (88-255) words selected
by C/s-2 being low. This is the area allocated to hold the ASCII
, codes of eighty-four recogniæed characters and the corresponding
; scan count at the time at which the write command for that
character was given. The writing and reading of data in this
~; 25area i9 usually a double-cycle sequence. When data is read out
to the output device, only single-cycle commands are used to
. ~ .
extract the character codes since the scan position is no longer
of interest.
.
111
.
,. , , ~ . . , . . . . .. .: . .. .
::. . . - . , . : :. .
........... :: . . . : .....
47
III(A.ll.e) MEMORY COMMANDS
There are ten distinct memory cycle commands which
can be generated during the operation of the system. These
are outlined as follows:
a. MCMA - (RPSl-INH) - This is the command which obtains the
vertical format data from the memory during a document read
cycle.
b. MCMB - (ODRQ) - This lS the command which requests character
codes from the memory for transmission to the output interfaceA
c. MCMC - (Read HORZ F'ormat) - This is the command which requests
horizontal format data from the memory during a document read
cycle.
d. MCMD - (Read Search) - This is a command which is generated
during RPS9 and RPSllof the read program to search through
,
the data portion of the memory to find the first character
with a "character unrecognized" flag.
e. MCME - IWrite Vertical Format) - This is a command which is
!
generated during FPS6, 11 and 13 of the format program to
~ wr~te vertical format data into the memory.
,~ 20 f. MCMF - (Write Horizontal Format) - If the unit is in thé
horizontal format mode, during FPS8 of the format program,
this command is generated to write the scan count and control
~: : :
; bits into the memory for the control of horizontal format.
g. MCMG - (Write data during RPS9(rescan) - During RPS9 rescan
.
on the read program, only those characters which were not
recognized dur~ing RPS6 are reread. Upon rereading, the
` recognized character codes or the~substitute code for un-
recognized characters is written intothe memory.
:: ~
112
.
, . ,, :
. .
,'`, ''' '''"'
~ , I~ ~F ~
s: u~ :~ ~ ~
~ ~ ~ - -- - - ~ ~
~ ~ ~ 7 ; ::
". I~ ~ ~ ~ ~ ~ ~ ~, ~ ~ ~ ~:
~ . 1~ ~ 3 ~ ~ . ~ ~ ~ ~ 5 ~ i ~ '
:~: ~a ~:: ¢ ~1 -I o o o_~ o o o o o o .
X I---- h -- -- _ _ ~
~: ~ .'S ~1 O --I O _ _l O _~ --~ --i _1 ~1
_ ~ I m __ _ _ _ ~3
. X a _ _ ~ _~ o o _~ o o o ~.
, ¢ L~ __ _ _ ~ _~ o _ ~ _. o
o ~ l ~ l ~ ~ ~ ~ l ~ t~ .
. _-- ~ ~ _ . _ . . _ _ ~:
~ 8 u~ u~ u~ a u~ u~ u~ u~ u~ a
IE~ _ _,_ _~r ~
3 ~ ~ ~1 ~ ~ 3 3 3 3 3
_ _ ~ _ u~ _
V ~ I ~o ~ ~
~ ~ - Y U ~ _ ~ ~ ~ ~ ~ ~ .
-113-
...
' ~
, :.......... .. , , : , . . :
. , : . ' . ,: ,. :
)4~
. . .
h. MC~ - (K~yboar,d WRITE) - This is a memory write comman~
generate~l by a keyboard entry during RPS13 or RPS15 of
the re~d program.
i. MDMI - (MEM FILL) - This is a memory write command which
5 ~ c~n be generated during RPS6, 9, 13 and 15 of the read
pro~r~m. It is used to fill the data portion of the memory
with bl~nk character codes following the last data character
entered.
~. MDMJ - (Write data during RPS6) - This is a double memory
write cycle. The unit scans a line during RPS6 of the read
pro~ram to attempt to read all characters in specified areas.
Write commands from the recognition circuit caus~ the code
and horizontal scan position of the character to be written
Into memory.
1~ III(A.ll.f) TIMING
Timing for the memory cycles is illustrated in the
timing diagram of Figure 35. Memory controls and timing
circuits are illustrated primarily in Figures 54-63. The
following description relates primarily to these figures.
~20 The four read cycle commands MCMA, MCMB, MCMC and
MC~D are OR'D, together by gate 6001 and inverter 6002 to
initiate a read memory cycle, The qix write cycle commands
. . _ .
, ~ MCMF, MCME, MCMG, MCMH, MCMI and MCMJ are OR'D together by
', gate 6003, which is part of a flip-flop with gate 6004,
and inverter 6005 to initiate write me~ory cycle~.
Two memory commands MCMD and MCMJ are OR'D together
,
..
,.' . .
~ 114
. - , ,, ... . . , _ .
. . ': j....... , . , ''' ' , .' , '. : ' ~ ' ~
by gates 6006 and 6007 to generate double-dycle command3; the
other eight memory commands are single-cycle.
When a memory cycle command i9 ini~iated, the output
of ~ate 6001 goes high and the output of 6002 goes low. If
gate 6001 is high when MCYC (memory cycle complete~ iY high,
gate 6008 enables the J input of flip flop 6009. At TPE time,
gates 6010 and 6011 generate a clock pulse to change flip flop
6009 to the one state. This initiates the MCCl portion of the
memory cycle. On the following TPE pulse the same circuit~
generate another clock pulse to set flip flop 6012 to the one
state. This initiates the MCC2 portion of the memory cycle
operation. If thi~ is a double-cycle memory operation, gates 6006
and 6007 would inhibit the K input to 6009, maintaining MCCl and
MCC2 until the next IPE pulse. If it i a single-cycle operation
lS MCCI would be reset when MCC2 goes on.
During a double-cycle operation MCCl and MCC2 are on
until the next TPE pulse when the MCC2 signal at gate S007 allows
flip flop 6009 to return to the zero state and terminate MCCl.
MCCl on and MCC2 off defines the read/write portion
~ 20 of a single-cycle operation,~or the first cycle of a double-cycle
,~
operation. Both MCCl and MCC2 on define~ the second read/write
part of a double-cycle operatlon. MCCl~off and MCC2 on indicate~
~; that the memory cycle is complete tMCYC). For timing purposes
a memory cycle complete delayed~(MCYCDL~ signa1 is generated by
flip flop 6101. _
~Cys ~
he~eYS~ signal (Memory cycle~ start) i~ g~nerated by
qate 6021 when either MCCl or MCC2 are on to indicate that a
~¦ memory cycle is in process. ~ ~
1, .
~l 115
104~7
The write command R~W is generated at the required
times by gates 6003, 6004, 6015; inverter 6016, flip flop 6017.
The various timing pulses during the memory cycles are generated
by gates 6102 through 6106 in Figure 61. The RDSTl signal from
gate 6102 is used to gate memory output data into registers at
the end of the first memory cycle. The DASTl signal from gate
6104 is used for various testing or gating of data previously
stored in the registers. Signal RDST2 from gate 6103 gates memory
output data into the output register at the end of the second
part of a double memory cycle.
Signal MCYCPF from gate 6106 and signal MCYCPB from
gate 6105 are used for various functions at the end of the memory
cycle.
Memory cycle complete (MCYC or MCYCDL) are used to
indicate the end of a memory cycle and signal the removal of the
memory cycle command. The initiating command must be deactuated
if the control logic is to cycle and turn off MCCl, MCC2, MCYS
and MCYC.
Six of the memory cycle commands (MCMA, MCMB, MCME,
MCMF, MCMH, and~MCMI) cannot occur simultaneously with each other
or any of the other four cycle commands. Memory cycle commands
i ~ MCMC, MCMD, MCMG and MCMJ cannot occur simultaneously with the
other six but could possibly occur simultaneously wlth each other.
Therefore a priority circuit has been provided in Figure 56.
III(A.ll,g) MEMORY CHIP SELECT
Refer to Table Ml and gates 6301-6304 for the require-
.
ment and circaits to generage chip select C/S-l and C/S-2 signals.
.
116
,
~ '
.
~~
III(A.ll.h) DATA MULTIPLEXER SELECT
Refer to Table Ml and gates 6305, 6306, 6307 for the
requirements and circuits to generate the data select control
bits DSA and DSB The actu~l data multiplexer is illustrated
i 5 in Figure 26. Data sources are discussed in more detail in
another section.
III(A.ll.i) ADDRESS MULTIPLEXER SELECT
Refer to Table Ml and gates 6308-6312 for the require-
ments and circuits to generate the address select control bits
ASA and ASB. The actual address multiplexer is illustrated in
Figure 48. Address sources are discussed in greater detail in
another section.
III(A.ll.j) REGISTERS AND PULSES
There are three memory data output registers. The
MDR register in Figure 44 is a 10-bit register which holds data
codes and vertical format data~ The HCR register in Figure 27
is a 12-bit register which holds horizontal count data for
horizontal format control. The EPR register in Figure 27 is
- an ll-bit register to hold horizontal count for unrecognized
character RPS9 rescan during the read program.
Refer to Table Ml and gates 6308, 6310, 6313, 6314,
6315 for the requirements and circuits for generating the MDRST
signal which is used to gate data into the MDR register.
Refer to Table Ml and gates 6316, 6317 for the re-
quirements and circuits for generating the HCRST signal which
is used to gate data into the HCR register.
Refer to Table Ml and gates 6318, 6319 for the require-
ments and circuits for the EPRST signal which is used to gate
data into the EPR register.
117
:~ ,
, ' ' . .
: .
9~7
III(A.12) DATA MULTIPLEXER
DATA SOURCE
The data multiplexer is illustrated in Figure 26.
Logic associated with the data multiplexer is illustrated in
Figure 3~.
Table M2 shows which data sources are selected by the
six memory write commands MCME, MCMF, MCMG, MCMI, and MCMJ to be
placed on the 1~ memory data input lines MDI-l through MDI-12.
There are four primary data sources:
; 10 a. Recognition circuit data codes RDCl-RDC8
b. Scan counter output SCCl-SCCll
c. Document advance step counter DACl through
DAC7 and DAT177
d. Keyboard input Code KDCl-KDC8.
These are generated as follows:
a. Recoqnition Circuit Data Codes
;r The 8-bit ASCII (odd parity) data codes are
generated by the Recognition Circuitry and are transmitted to
the circuit of Figure 26, upon request, during RPS6 and RPS9 of
the read program. The 8 bits RDCl-8 are so transmitted with a
write command OCRW, which is received at the circuit of Figure
~ 56 where it initiates memory cycles MCMG and MCMJ.
.
b. Scan Counter
: : _
The scan counter (Figure 28) consists of three
counter sections 2801, 2802, 2803. The clear signal (SCCLR)
.
and the count pulses (SCCI') for the counter are generated in
the circuits of Fiqures 36 and 37, respectively. Scan Counter
.'
118
,
"~ ., .. , ,. ,. . ;, - : ,
,' '
,
- ~u ~
~ C~ U ~ 8 C~ V O c~ C~ o
I~ H ~ U~
:~ __ .__ h
.~D ~ ~ ~ ~ ~ ~ u~ ~D i` )
H ~ a a ~ ~ ~ o o .~ ~'
_ . .
. H ~ ~ '~:
3~ ~ o o o o o o o o 1 ~1 1 o o o ~ 3
~
P~ ~i H ~ 30 o
q~
~¦ a Ll ~ o ~ ~ ~ v ` o
. . O O H
~1~ a 3 ~1 o ¦~! O O O _ .
, I . .__ ~ , 4~
~ o U ~_) u V O V V C~ ~ O
. ~ u~
. ~ ~ ~ ~ ~1
~ ~u~ ~ ~oooo h
.~ . . . ..... - .___ __ _ ~
:~ I __
119
.~ ' .
. : ~ ' ..
~:34~7
Clear (SCCLR) is generated by gates 3601, 3602 during format
program step FPS7 and -read program steps RPS5, RPS8, and RPSll,
all of which occur previous to enabling of the scan counter.
MPS5 keeps the scan counter reset until the format and read
program counters are enabled.
Scan counter coun-t pu]ses (SCCT) are generated by gates
3701, 3702 and 3703. MUX 63 is a pulse which occurs every 64th
TPF pulse; this is the horizontal scan sample frequency. The
SCSP (scan stop) signal is normally high until the scan counter
reaches a predetermined count selected by the document width
selector. BOL (beginning of line) is a signal from a mechanism
photocell (phototransistor Ql) whlch senses a window in the cam
which operates the scan mirror. BOL is low when the cam positions
the mirror at a dwell when the scan is at the left hand margin
of the page. When the clutch and brake are engaged the cam is
coupled to the synchronous scan motor 8717. BOL goes high just
before the cam follower comes off the dwell and the mirror begins
its scan. This provides a consistent reference point at which
to begin the scan count during each scan.
Gates 3801-3803 generate the SCAN CONTINUE signal during
read program steps RSP6, RPS9 and format program step FPS8 to
initiate the energization of the clutch/brake 8715, 8716.
SCAN CONTINUE goes to gate 3703, which actuates gates 3704 and
3705 to provide the clutch/brake energize signal~ Gate 3706
insures that the clutch/brake stays energized until the cam
.~ window returns to BOL except during read program steps RPS12
.
,
120
~ I .
: ' ,. . .
.. . . .
nd RP513. Th~se are the two program count steps which control
the mlrror to polnt to an unrecognized character in the Error
Halt mode to allow for keyboard entry.
Gates 3802 and 3804 set a flip-flop 3805, 3806 at an
early scan count to enable the SCDR (scan duration) signal from
gate 3807. SCDR in turn provides a RDEN tread enable) signal,
via the circuit of Figure 43, to the Recognition Circuits. Gates
3808-3811 set flip-flop 3812, 3813 at different counts and
conditlons to provide the SCSP (scan stop) si~nal and turn off
0 the SCDR signal. During format program step FPS8 scan counts
are stored in the memory to provide begin and end of field
positions. During read program step RPS6, each data write command
(OCRW) from the Recognition Circuitry causes the character code
~and character scan position count to be stored in memory
.5 ~refcrcnce gates 5501-5503, flip ~604J and Figure 28)o
c. Document Advance Counter
The document advance counter is illustrated in
Figure 84 and consists of a series of gates to control the 7-bit
counter 8406 and 8407 and to generate the DCMT (Document Motor
Toggle) pulses~ This counter circuit serves two purposes. During
~ format load it counts the steps of motor 500 required to advance
': the document at the read st~tion from the top edge to the first
line mark, and the number of steps ~o advance to each succeeding
line mark. Vuring read mode the counter controls the number of
steps required to advance the document from line to line. During
format load the seven output bits DAC1 through DAC7, and the
"all ones" condition DAT177, are used. In general the format
., ' ~,
'
121
. .
P~14~7
program counter advances the conditioning document until it
~enters the llne mark in the read array or the counter reaches
all ones; i.e., DAT177 goes low. When a line mark i~ centeréd
in the array, a memory write cycle (MCME) is initiated which
writes a number into the vertical format portion of the memory.
The number represented by DACl-7 is neither all ones nor all zeros.
and DAT177 is high and therefore is written into the memory as a
one. If the counter ~eaches all ones before finding the next line
mark, ~he document advance command must be written into memory,
but ~s accompanied by a flag to command the advancing of the
document without a command to read a line. In thi~ ca~e signalq
DAC1-7 are all ones and DAT177 is low at gate 8411, which results
in a zero being entered for this bit. With continued advance of
the f~rmat document, the end of the document eventu~lly appears~
and a command must be written into the v~rtical form~t memory
pOsieion to indicate this. When the end of d~cu~nt app~ars the
format prog~am counter causes the docum~nt adva~ce counter to be
; reset to zero and a MCME memory write command i~ initiated.
Signal~ DAC1-7 all become zero and DAT177 b~come~ high.
O During re~d prograun mode step RPSl, r~ad v~rtic~l
format memory cycles (MCMA) are initiat~d. ~h~ 7~bit count
(DACl-7) is obtained ~rom the m~mory and it~ ones ~mpliment i~
used to preset the document advance count~r 8406,8407. The bit
corr~-ponding to DAT177 is desi~nated MDAF8 ~nd is gatod by ~-
ga~e 1701 and stored in flip-flop 1702, 1703. ~hr~ op~ration3
can ro~ult rom this vertical format d~t~ D~Cl-7 i9 not ` ~ ;
all zeros or not all ones and DAT177 (DA~ at gate 1702 output3
~ 122
., . ; .
. . ' ~. ~-. .. . .: ~
, . . : :. . ,
. ., ~ . ., : .
. . : . . . ~ :'
is high, this is an indication that the document should be
advanced to read a line. The control circuits advance the
document motor 500 the number of steps required to make the
counter output (DACl-7) all ones, forcing DAT177 low. When
such conditions exist the document has been advanced the number
of counts originally determined by the conditioning document.
If the original count DACl-7 had been all ones, forcing DAT177
low, presetting the counter to the ones complement from the
memory places zeros into the counter. DAT177 being low or zero
results in DAF8 at flip-flop 1702, 1703 being low. This then
causes the document to advance the number of steps to again make
; DACl-7 all ones and DAT177 low. With DAF8 having been set to
7ero there is no command to read a line. When the end of the
document is reached DACl-7 is set to all zeros. When this is
read out of memory and its ones complement is preset into the
count, the counter becomes all ones. DAT177 had been high during
the write command so DAF8 becomes high. As described in
` ~ reference to read program counter operation, RPSl obtains the
vertlcal format count from memory and places the ones complement
20 ~ into the counter. RPS2 examines the DAT177 output gate of the
¦ counter. If DAT17~7 is low the present contents of the counter
is all ones, and the count read out of memory is all zeros. This
,,
r ~ sets the Read Complete flag. If DAT177 is high, the read program
~ ~ counter continues for further processing.
L
The document advance counter is also used during the
document pick process to count the number of steps required to
cover the skew station photocells. The count starts after one
,
123
:
., . , , ~ ~
of the photocells is covered and stops when two are covered. At
three lines per inch operation, two steps are allowed and three
steps are considered a skew error (SKER goes low at gates 8401,
8402). At six lines per inch, one step is allowed and two steps
is a skew error.
During load format, when a line mark is found and the
step count is written into memory, the document is advanced a
fixed number of steps before the system looks for the next line
mark. At three lines per inch the document is advanced twelve
steps and at six lines per inch it is advanced six steps. The
line called DAT12 from gate 8412 and inverter 8413 indicates that
the counter has reached the count of 6 or 12 as required.
; d. Keyboard Input Code KDCl-KDC8
; The keyboard data input is used primarily duringRPS13 in the read program for the manual entry of unrecognized
characters. The keyboard code comes through inverters as
illustrated in Figure 80 and from there go to the data multi-
ple~er in Figure 26. During RPS13 and RPS15 the keyboard entries
generate memory write commands MCMHo
III(A.13) ADDRESS MULTIPLEXER
The memory is partitioned into vertical format, data,
and horizontal format sections which are discussed elsewhere
herein. These three sections have independent address controls
for which appropriate counters are provided.
The vertical format address counter is illustrated
in Figure 52 and consists of 7-bit counter 5201, 5?02 and
output gate 5203. The counter is held in the reset condition
.
124
'1 '
,, . . , "
- , . ~ ' ,, , ' ~ :
except during step MPS5 of the master program operation when
either a load format or read operation is progressing. Signal
VFADT is the count pulse which is generated by gates 6018, 6019.
During format load, a memory write cycle signal MCME causes a
VFADT pulse to be provided at the end of the write cycle. During
document read a memory read cycle signal MCMA causes a VFADT
pulse to be provided at the end of -the memory cycle. Gate 5203
generates a signal VFAT86 when the vertical format address counter
5201, 5202 has reached a count of 86 and exceeded the allotted
count. The data address counter is illustrated in Figure 50 and
includes counter elements 5001, 5002 and associated gates. At
various times, as controlled by the signal ADSO into gate 5003
and the KBCLR signal at read program step RPS15 at gate 5004, the
data address counter is preset to a count of 44. The low order
bit of the counter DADl is gated in Figure 48 as the second
least significant bit of the memory address MAD-2; similarly
the other counter bits are displaced. This has the significant
effect of multiplying the starting address by two. The data
address represented by DADl-DAD7 thus starts at memory position
88. Certain of the data memory cycles are double cycle opera-
tion where data codes are written into or read out of the memory
on the first part of the cycle, and the scan count position of
the character is written into or read out of the memory on the
¦ second part of the memory. That is, addresses 88, 90, 92, etc.
contain character codes whereas addresses 89, 91, 93, etc. contain
scan counts SCCl-SCCll. A signal MCC2 is generated by the memory
controls to go high during the second part of a double cycle
:
- 125
~emory operatlon. This signal goes to the address multiplexer
(Flq. 48) to act as the low order bit (MAD-l) of the data addres~.
A line complete signal is generated after 84 data write or read
~ commands. That is, the counter starts at 88 and adds 2 x 84
memory cycles for a final count of 256. The counter i~ advanced
by the DADT signal (data address toggle) which is generate~ by
gate~ 5401-5404 in the memory control circuitry. The horizontal
add~s~ counter consists of counter elements 5104, 5105 and
asso~lated circuits in Figure 51. The horizontal format has been
allocated 256 words of the data memory; therefore it require~ a
full 8-bit address count. The counter i5 normally held in the
clear ~tate except during step MPSS of the master program.
Durin~ load format mode, at the end of document, FPS14 of the
format program acts through inverter 5303 to stor~ t~e l~st
horlzontal fonmat addre~ u~ed in storage units 5301, 5302.
-
. During document read operation this la~t u~ed fon~t addre~s is
compared with the addres~ counter by gat~ 5304 through 5312.
:~ When the last addres~ i ræached during read operation, this
~ircuit, with inverter 5313, ~ign~l~ that th~ horizont~l field i~
.
O complete and, eventually, that read oper~tion i8 complete (via
: j
. gate 2106).
.
Due to th~ rescan feature it~ ia n~ces~ary to be able
to re~tore the horizontal format addr~s or the b~ginning field
of each line. Ther~fore, at RPSl time in th~ read progr~m, the
~5 horizontal ormat addre~ stored in m~ory unit~ 5106, 510~. -
At RPS5 and RPS8, just before read cy~lo~ RPS6 and RPS9,
. .
resp~ctively, thiq stored count i~ pre~ot into the counter
.
'- :'
126
, .
.:
510~, 5105 via ~ates 510~-5111. During a normal read operation
the read program counter goes in sequence. RPS0, RPSl, RPS2,
RPS3, RPS4, RPS5, RPS6, RPS7 and back to RPS0. The address
count is stored in the memory units 5106, 5107 at RPSl, the
counter is preset during RPS5, the counter is advanced during
RPS6 and the new count is set in the latches at RPSl, etc.
With a rescan, the sequence goes from RPS7 back to RPS5 and
then to RPS6. This bypasses RPS1, and at RPS5 the previous
initial count is restored to the address counter 5104, 5105.
This also occurs during RPS9 rescan, returning to RPS7 and then
RPS8.
The horizontal address counter is advanced by the HFADT
signal (horizontal format address toggle) via gate 5110. This
signal is generated by gates 4302, 4303, 4304 and 4305. Gate 4302
advances the counter at the end of a memory write cycle during
step FPS8 of the format program; i.e. during format load.
Gates 4303 and 4304 generate the advance pulses at the end of
memory read cycles for horizontal format. The HCR10 signal is
derlved from the memory bit which indicates that horizontal format
data is the beginning of the first field of a line; this must
occur with the first field of line flip-flop 4306. As the
~eading of a line progresses and the horizontal format control
is read out of memory, eventually the data for the first field
of the next line is read out with signal HCR10 high. This
inhibits the horizontaI format memory address counter so that
the counter is at the correct address for the beginning of the
next line.
:
~ 1~7
, ~,.. , :
lII(A~14) VERTICAL FO~MAT
Write and Read Operation
Referring to the outline for the Format Program Counter,
steps FPS6, FP~ll and FPSl3 are memory write cycle~ for vertical
format. These three si~nals are "or'd" together at gaee 2003
to ~enerate a memory cycle signal MCME via inverter 2004. This
siqnal in turn goes to gate 6003 in the memory controls to
initiate a singl~ cycle memory write operation. The Data
Multiplexer selects the Document Advance Counter as the data
source and the Address Multiplexer selects the Vertical Format
:.
Address as th~ ~emory address. The memory cycle complete delayed `
.
(MCYCDL) signal from flip-flop 6101 enable~ the format program c~unT~r
to ad~ance, and the vertical format address counter is advanced.
The th~ee different possible data contents and their meaning,
a~ obt~ined from the document advance counter, are described
. i `
~erelnabove.
Referring to the outline for the Read Program Counter,
step RPSl réquires a ~emory read cycle or vertical format.
Gates 4307, 430a, 4309 generate the RPSl-INH (MCMA) si~nal which
is the Read Vertical format memory command. When RPSl goes high,
- gate 4309 provides a negative MCMA Signal which initiates the
memory cycle at gate 6001 in the memory controls and inhibits the
advancement of the Read Program Counter ~t gate 1602. At
the memory cycle complete time, signal MCYCPB re~ets flip-flop
4307, 4308 and turns off MCMA, allowi~g th~ Read Program counter
to advance. The use of the memory output to pre~et the document
advance counter to the ones complement ha~ been described herein-
above.
-,
128
: ~, ' . ~:
, ~ . ' ,: , ' :
III(A.15) RECOGNITION DATA
Write and Read Cycles
There are four different memory commands associated
with the data from the Recognition Circuits. They are as follows:
a. RPS6 - Original scan and read of complete line
b. RPS9 - Rescan of previously unrecognized characters
c. RPSll & RPSl3 - Keyboard entry to replace un-
recognized characters.
d. ODRQ - Output data request from peripheral interface.
a. Memory cycle signal MCMJ is generated in the circuit of Figure
56 during each RPS6 read enable period by OCRW commands from the
recognition circuits. MCMJ is a double cycle write memory
operation. During the first half cycle the ASCII code generated
at the Recognition Circuits is written into memory. On the
` 15 ~ second half cycle the scan count (SCCl-SCCl1) associated with the
`,; position of the recognized character is written into the next
,, .
1 ~ ~ memory word position. Refer to Table Ml (memory cycle summary)
. 1` :
for the data and address multiplexer operations. Memory cycle
,` ~ signal MCMJ is generated by gates 5601-5603 and flip~f1Op 5604.
tl~ 20~ b. Memory cycle signal MCMG is generated during each RPS9 on
~ rescan of previously unrecognized characters. MCMG is a single
t~
cycle~write memory operation. Memory cycle signal MCMG is
generated by ga~tes 5605, 5606, 5607 and flip-flop 5608. Data
:
, ~ and address sources; and multip1exer operation are s1milar to MC~J
25~ during~RPS6 and are described hereinabove.
; c. In the Error Halt mode, if there are still unrecognized
characters after four RPS9 rescans, the system projects the
.. ~
, ~
~: : ~ :
'~ 129
: ,:
'
" , ' ' ,
unrecognized character onto a screen for operator viewing. The
data address counter has been advanced to the address of the
unrecognized character. The unit system pauses at RPSll to
enable the keyboard for operator entry of a character from the
keyboard. The keyboard da-ta comes through the circuit of Figure
80 to the data multiplexer. The keyboard data strobe signal
(KBST) goes to gate 6201 to generate a write command K~DW. This
signal goes to memory cycle flip-flop 4502, 4503 to generate the
memory cycle signal MCMH.
d. When a line of recognized data is ready to be transferred out
of the system, the buffer full (BUFFL) signal from gate 5507 goes
to flip-flop 7307, 7308 and, via gate 7311, initiates data output
__
se~uences. BUFFL enables the line data available (LNDAV~ signal to
the output unit. Data Request signals from the output unit
generate the output data request signal (ODRQ) at ~ate 7312
and inverter 7313. These signals initiate memory read cycles
for data to be placed on the output interface. ODRQ commands
generate MCMB memory cycles. Table Ml shows some of the require-
~"~ ments for this operation.
; 20 III(A.16) HORIZONTAL FORMAT
Write and Read Operation
The horizontal format memory operations consist of
`' write cycles during load format program count FPS8 and read
cycles during read program counts RPS6 and RPS9.
a. FPS8 - Write Operation or Load Format
During format load with horizontal ~ormat control
I the system positions the conditioning document at each vertical
`I 130
. .
.. . , , . . .,: . . .
',' .: ,.. .' , ... ' : , ,.. ,, ' ,' . ' : ,
:. . , , . .. ' : : : . '
format line mark. At each line the unit then scans across the
line to read the field-identifying character. For each field
there are begin and end of field characters. The position of
the characters, as defined by the scan count (SCCl-SCCll) at
the position the character is recognized, defines the begin and
end positions of the field. The characters printed on the
conditioning document are used to define various parameters
for each field. Referring to Table M2 "Memory Data Multiplexer"
and the column for memory cycle MCMF, it is noted that only the
nine high order bits of the scan count (SCC3-SCCll) are stored
in memory to define the field position. The horizontal scan
counter is counting at a rate of 145 character slices per inch.
For OCR-A font characters at ten pitch, each character is equiva-
lent to 14.5 slice counts. By dropping the two low order bits,
the variation of field position may vary a maximum count of
I three out of 14.5,or approximately 1/5 of a character space.
~ This was done to conserve memory. It is possible to expand the
; memory word length from 12 to 16 bits; in doing so, the ten high
- l order bits of the scan count ~SCC2-SCCll) can be stored and only
`l 20 the low order bit SCCl would be dropped. This would provide
better precision in defining the begin and end positions of the
field.
Referring again to the same columns of Table M2, it
is noted that memory input bits ll and 12 are the two low order
2S bits (RDCl, RDC2) of the ASCII code for the character which has
been read. This means that the begin of field character can
specify four conditions or parameters, and the end of field
......
;~ 131
I .. . . .
. .
~4~7
character can specify 4 more. The system as disclosed is set up
for the following control by the begin of field character:
Character RDC2 RDCl
0 0 0 Handwriting
1 0 1 Not assigned
2 1 0 Farrington 7B Font
3 1 1 OCR-A Font
The two low order bits of the end of field character are pre-
sently used to control the pitch (characters per inch) parameter
and the mark sense control. Each of the fonts has the two
following pitches:
OCR-A 10 and 8 characters per inch
Farrington 7 and 6 characters per inch
Handwriting 5 and 4.3 (4.0) characters per inch
The low order bit RDCl controls the pitch. If RDCl=0, the higher
density pitch is selected; if RDCl=l, the low densith pitch is
~ selected.
,~ ~ The second end of field bit (RDC2) is used to control
the mark sense. If RDC2=0, any extraneous marks or other
, 20 conditions which result in an unrecognized character cause the
, system to operate in the normal rescan mode, with the results
¦~ determined by Operate Mode Switch. If RDC2=1, it is anticipated
that this is a mark sense field wherein a mark results in an
unrecognized character, or the OCR-A s~mbol for overstrike.
The substitute code for an unrecognized character (underline)
or the code for the overstrike is placed in memory. In this
case the read error flag is inhibited for this field, and no
rescans are requested.
132
- . . ' ' , ' . . . . .
If the memory-word size is expanded, the four low order
bits RDCl, 2, 3, and 4 of both the begin and end of field
characters can be stored. Table M3 shows a possible assign-
ment of the functions and parameters to be controlled by the
begin of field character. The end of field character bits are
left unassigned, and are available for any function to be added
in the future.
One bit of the horizontal format memory word is used
to identify the first character of the first field of each line.
This is required to separate the groups of horizontal format
words of each line. It is possible to provide a memory parity
bit to make the 16-bit word odd parity. The system as disclosed
has a parity bit for the ASCII data codes only. This can be
retalned if the additional parity bit is used but the added
parity bit enhances the integrity of the vertical and
horizontal format control. The FPS8 memory cycles (MCMF) are
initiated at gate 4302 by the OCRW write commands from the
Recognition Circui-t.
bo RPS6/RSP9 - Read Operation of Horizontal Format.
The circuits for controlling the memory read
operations for horizontal format are illustrated in Figure 43.
I The operation consists essentially of obtaining the format word
; for the beginning of the first field and storing the scan count
bits from the memory in the ~CR register of Figure 27. The
¦ 25 output of this register is compared with a modified ~can count
1 :
1 133
~'
.. . .
. .
i. ~..~ ~
TABLE M3
HORIZONTAL FORMAT
BEGINNING OF FIELD CONTROI, CHARACTERS
, _ ,
E-~EX Code Usable Control CONTROLL~ D FUNCT rONS .
of 4 LSB Characters Font Pitch LPI Mark Sense
O O P OCR-A 10 3 No
¦ 1 1 A Q OCR-A 10 6 No
2 2 B R 7B 7 3 No
. 3 3 C S HAND 5 3 No
: 4 4 D T OCR-A 8 3 No
E U OCR-A 8 6 No
6 6 F V 7B 6 3 No
7 7 G W HAND4.3(4.0) 3 No
8 8 E~ X OCR-A 10 3 Yes
1 Y OCR- 10 6 Yes
12 L OCR-A 8 3 Yes
8 6 Yes
~.
,1 ,
.,1
I
! 134
, ~
:\ ~
SCC3 and SCC4M through SCCllM by the exclusive-OR circuit~ at
the top of Figure 33. When the modified scan count equals the
count in the HCR Register, the signal "HZ SCAN COMPARE" is
obtained from output gate 3301. This signal goes to gate 4310
to operate flip-flop 4311. With the flip-flop toggled to the
one state, the Read Enable (RDEN) to the Recognition Circuits
is turned on and a request is made to the controls to provide
the next horizontal format word from memory. Again this word is
stored in the HCR register, replacing the previous count. When
the modified scan count equals the count in the HCR register,
the "HZ Scan Compare" signal toggles flip-flop 4311 back to the
zero state, turning off the RDE~ signal, and thereby requesting
~` the readout of the next horizontal format word from the memory.
Each time a new horizontal format word is obtained from memory,
memory bit number lO,which is stored as HCR-10 in Figure 27, is
; examined. If HCR-10 is a one (high), this indicates that the
.;
j current format word is the first horizontal format word for a
line. When initially going into RPS6, ~PS9 and FPS8, flip-flop
¦~ 4306 is res~t to a zero condition. Thi3~ flip-flop (First ~ield
i ~ . .
of Line) i~ W ed to orce the acceptance of the fir~t hori~ontal
format word from the m~mory and enable8 the g-neration of a
horizontal ormat addres~ count pul~e (HFADT àt gate 4305.
. '~ Flip-flop 4306 is tioggled to the 0 ~ slte tat~by~the ir~t
; ~ HFAD~ ~nd stays;~ther~e~until the system~gooo Oue o~ ~t-p~ RPSi5,
~5 ~PS9,~ or~FPS8. ~With~ his flip-flop in thQ~t~g~læd posi~ion,
FADT lS generated fo~:~only those horizontal~ format words in
j ~ which KCRl0 lS zmro ~low)~.~ If ~CR10 ~ high, flip-~lop 4312,
135
, ~
4313 is set and prevents generation of further read enable signals
Eor the remainder of the scan in operation. HFADT is also
inhibited so that the horizontal format address counter stays at
-the last address. When the next line is scanned, the address for
the horizontal format word is the correct one.
Previously it was noted that the contents of the HCR
register (Figure 27) were compared with a modified scan count.
; Since the conditioning document requires a printed character for
begin and end of field, it may appear that the end of one field
and the beginning of the next must be at least one character
(or 0.1 inch) apart. The effective end of the field is stretched by
the following method. In Figure 39, gate 3901 and 4-bit adders
3902 and 3903 subtract a count of 8 from scan count SCC4-SCCll
to provide a modified count of SCC4M-SCCllM. This is only per-
formed when HFADl is low; that is, when the state of the low
order bit of the horizontal address counter is low while
waiting for the end of field. By substracting eight from the scan
count, the counter must go an extra eight counts before the end
.~
of field horizontal scan compare signal is obtained. Therefore,
the end of field is stretched eight counts. At the highest
density pitch of ten characters per inch, each character position
is equivalent to 14.5 horizontal scan counts.
Memory read cycles for horizontal format are initiated
by the signal '!EN RD ~Z FT" generated by flip-flop 4314, 4315.
This signal goes to the memory priority circuits 5609-5611 to
generate memory cycle signal MCMC. Refer to Table Ml memory
cycle summary for various functions for this memory cycle.
,1
136
- ,
For horizontal format memory read cycles, memory
output bits MDO-l through MDO~10 are gated into registers 2701,
2702 and two of the four bits of register 2703 by the signal
HCRST. Memory output bits MDO-ll and 12 are gated into the other
two bits of 2703 by the HCRST signal gated with signal HZADl
being low at gate 3202. This provides storage in HCR-ll and
HCR-12 of the two low order bits of the format character
designating the beginning of field. The two bits of the character
for end of field are stored in register 2901 via gate 2902 at
HCRST time when HZADl is high. As a result o~ the timing of the
operation these control bits are always available during any
Read Enable times.
III(A.17) RESCAN (RPS9)
The previous paragraphs described the horizontal format
operatlons during the full line read cycle of RPS6 and the
~ unrecognlzed rescan cycle of RPS9. The same horizontal field
;~ position and control information is needed during RPS9 as RPS6.
The essential difference during RPS9 is that a search is made
through the memory to look for the unrecognized character flags.
When such a flag lS found the associated scan count position of
that character is also read from memory and placed in the EPR
, register 2704, 2705, 2706. This count corresponds to a position
just to the right of the unrecognized character and it is
l required to actaate Read Enable at gate 4316 at a position just
; 25 to the left of the character. This is accomplished by~three
i 4-bit adders illustrated in Figure 40, which add variable counts
! to the scan count depending on the pitch of the characters.
,.~
137
Z
, , , ' :.
This modified coun-t (SCClP-SCCllP) goes to exclusive-OR circuits
in Figure 33 and is compared with the count in the EPR register
2704-2706. When the counts compare, a signal "ERR SCAN COMPARE"
is generated by gate 3302.
The read search process for unrecognized character is
performed by circuits illustrated in Figure 54. RPS9 going
high enables the output signal RD SEARCH from gate 5405. This
signal goes to gates 5612, 5613 at the memory priority circuits
to generate the memory cycle signal MCMD (see Table Ml for summary
of operation). At memory cycle complet delay time (MCYCDL), gate
5406 inhibits gate 5405 and turns off the RD SEARCH signal.
MCYCDL resets and allows another RD SEARCH signal. This continues
until flip-flop 5407, 5408 is turned on by either gate 5409 (which
senses the unrecognized character flag) or the line complete
' 15 signal. If flip-flop 5407, 5408 is turned on by the unrecognized
character flag, the data address counter is not advanced (DADT
`` inhibited at 5404), any further RD SEARCH signals are temporarily
inhibited, and gate 5410 is enabled. At Error Scan compare time
gate 5410 turns on flip-flop 5411, 5412, which is the Read Enable
. ,~
flip-flop for error characters. Within a character time the
Recognition Circuits provide a write command (OCRW) for either
~, ~ a recognized or unrecognized character. This write command
during RPS9 initiates memory cycle MCMG from flip-flop 5608.
' The OCRW signal resets the Search Complete flip-flop 5407, 5408
and inhibits the RD Search gate 5405. As soon as the MCMG
memory cycle is completed the OCRW signal is removed and gate
~8
, . .
'
5405, generating the RD Search signal, is again enabled. This
continues through the data memory until the 84th character is
tested at which time the Line Complete Signal stops this process.
`' ~;
'''1
;~ ` ;
., :
.
139
: ' ' : '.
~ .' ' , . ~ ,
III(A.18) LINE POSITION ANALYSIS
a. General
The line position analysis circuits are illustrated
in Figures 66 through 7~ and perform three primary functions.
The first function is operative during format load when the
circuits perform an analysis of the format conditioning document.
This function involves the sensing of vertical format marks in
; the left hand margin of the document page, and also involves
providing an indication both when a mark is detected and when
it is centered in the array. This indication signals the format
program counter to take the document advance count and store
it in the vertical format portion of the memory. The second
functlon of the line position analysis circuits occurs during
the read mode. As the system reads a line it determines the
vertical position of the complete line of characters on the
document with respect to the array. If the line is not
perfectly centered in the array the circuits determine how far,
and in which direction, the line is off center. The system
then initiates a fine line procedure to reposition the line as
close to the center of the array as possible. If there is an
unrecognized character during a scan, the fine line adjust
procedure positions the line closer to the center of the array
for the rescan. In any event the line is repositioned with
respect to the center of the array before the next line is read.
The third major function of the line position
~ analysis clrcuits occurs when the system is reading at six lines
i per inch. Under these conditions a shorter scan region,
'I -.
I 140
I
.
~9~
consisting of a restricted number of the sixty photo-diodes, is
utilized. When reading at six lines per inch the system controls
a ver-tical window which enables only fifty of the signals from
the photo-diode array. The line position analysis, during six
lines per inch operation, determines the vertical position of
each sample of a line and provides a "line following" control.
That is, if the line is skewed either up or down with respect
to the array, the recognition circuitry is instructed to move
the vertical window. The fifty enabled bits then proceed up
or down to follow the line. This function significantly increases
the reliability of automatic reading at six lines per inch, which
is ~he spacing for single space typing.
The line position analysis circuitry performs its
function by accumulating data from the MUXSD (MUX serial data)
line. In the quantizer-multiplexer circuit in the recognition
circuitry, the sixty bits of data from the photo-diode amplifiers
are compared with an adjustable threshold level and the sixty
bits are then quantized into either black (ones) leve7 or white
(zeros~ level. These sixty blts are gated into a sixty-four-
bit shift register, and the two upper bits and two lower bits
of the shift register are forced into a white (zero) condition.
Therefore, the sixty bits of the photo-diode array occupy the
middle sixty bits of the sixty-four-bit shift register. The
quantizer-multiplexer circuit also contains a six-bit counter
which counts from zero through sixty-three. While at the count
of sixty-three, the counter generates a signal designated MUX63.
This is a signal which coincides in time with the trailing edge
: f
14
''~
~: '
of TPF. Another signal used in the circuitry is called MUX63G
(gated). This is generated by gating the MUX63 signal with the
TPF timing signal.
The sixty signals from the photo-diode array are
gated into a sixty-bit parallel holding register. These sixty
signals then are gated into the sixty-four-bit parallel to serial
shift register. The output of the shift register is shifted
continuously at the leading edge of TPA. The MUX63 signal
indicates when the last (or the sixty-third) bit of the sixty-
four-bit shift register is being shifted out. The quantizer-
multiplexer circuit then provides a serial string of data,
consisting of sixty-four bits, which scans sixty photo-diode
array from the top to the bottom of a line to be read. This
is the data which is gated and circulated into a sixty-four bit
shift register 6816 in the line position analysis circuits. The
recirculating portion of shift register 6816 consists of two
thirty two-bit MOS registers, the output of the first thirty-two
bit register shifted into four eight-bit serial-to-parallel
shift registers 6818-6821. Gates 6822-6828 sense the parallel
output from the shift registers to detect certain numbers of
adjacent black (one) and white (zero) bits. The output of gates
6824-6826 set and reset the SRQ flip-flop 6830. Within the
line position analysis circuits this flip-flop output signal
is called SRQ (serial register Q output). For the purpose of
the analysis described herein the SRQ output signal is also
identified as a mark. In load format a mark is defined as
seven adjacent black (or one) bits. In the read mode, a mark
142
is considered to be seventeen adjacent black (or one) bits.
During step FPS4 of the load format program, a line
position analysis is performed. Step FPS4 causes one vertical
scan period of MUX serial data to be gated (via gates 6806,
6807, 6808, 6814) into shift register 6816. During the next
period from one MUX63 to the next MUX63, the output of shift
register 6816 is analyzed to determine if there is a mark
(or seven continuous black bits) in the register. The circuitry
also determines the position of this mark with respect to the
center of the shift register. This analysis thus determines
whether or not there is a mark in the array and the relative
position of that mark. The results of this analysis are used
by the format load circuitry in a manner previously described
to control the progression of the format load program counter.
During steps RPS6 and ~PS10 of the read program, the
MUXSD (data) is gated into the shift register 6816. The gating
may remain open for many cycles of MUX63. This has the effect
of superimposing many scans of the MUXSD data on one another.
As it is being scanned across the shift register, the line is
divided into segments. These segments may consist of 0.8 inch
character portions of the line, or may consist of shorter
segments associated with fields in horizontal format. The
` ; effect of accumulating multiple scans of MUXSD into the shift
register of the line position analysis circuits is to effectively
take a segment of data and squeeze it sideways to render it the
~1 equivalent of one continuous vertical line. Normally the
tallest character of OCR-A font is approximately lS-20 photo-diode
143
i
, . . .
, ~, ' ~', ' ' , ' ', ,. . ' '
:, , . , . .. :.
elements high. If within any one segment the characters are
vertically misaligned or the line is skewed, th~ horizontal
projection of that section of line may result in a set of black
elements in the serial data which could be much higher than the
18 to 20 elements of a character. This effectively provides
the system with a horizontal projection of the black bits
occurring over the entire segment. The line position analysis
program counter consists of a three-bit synchronous binary
counter 6609. This provides eight steps, or LPS0 through LPS7,
decode~ by decoder 6628, for the line position analysis program.
LPS0 is a holding position in which shift register 6816 is
disabled or erased. The unit is enabled to advance from LPS0
to LPSl during the FPS4 step of the format program, and during
the scan duration steps RPS6 and RPS10 of the read program.
~ 15 Durin~ LPSl gates 6806, 6807, 6808, 6809, 6814, allow the
`, accumulation of MUXSD into the shift register.
Appropriate conditions, discuso~d below, command the
1 :
~¦; system to advance from LPSl; the succeeding program steps
` perform the analysis. On~ of the analyse~ in~olves counting
~ : ~ ,
(via counters 6719, 6720~, the number o~ zeros or white spots
~ - in the MUXSD, 9tarting at the top of the arrAy and stopping when
: the unit sees a nark or reaches a maximum~numbéx of~zeros. The
~, white or zero count at~the top of th~ zrray~ i9 tranRferred to
the "A" registers 7001, 7002. Whe n a~mark i8 detected, the
~ . :
zero counter 6719, 6720 is reset, and after the~ma~k passes
. ,
: out of the end of the shlft register~, ~h~ sero counter i~
' ~ used ~o count the number of zeros or white ~pot~followLng the
~ i
14~
I .
:, ' ' .
mark up to the end of the MUXSD data strea~. Another register,
designated the "Bi' registers 7003, 7004 is utilized to store
the minimum count of the number of zeros detected below the
mark MUX63 is used to synchronize the beginning and end of
S th~ MUXSD data stream.
The line position analysis circuits also contain
another counter called the mark center counter 6706, 6707.
This counter is used to determine the center of any mark in
a se~ment with respect to the top of the array or the beginning
of the MUXSD. This is accomplished by counting all the zeros
or white spots above the mark and half of the black or one bits
of the mark. After the mark is shifted out of the shift register
6816, the system no longer counts zeros entering the mark
center counter 6706, 6707. A~ter processing one cycle of the
accumulated data in ~hi~t register 6816, thD mark center
counter contains a count which indicates the center of ~he mark
with respect to the top of the array. ~hi-~ count i8 utilized
in the "line-following" pr~cedure= of rcading at six lines per
inch. ~ounter 6706, 6707 is also utiliæed: during~ ~teps `RPS6
and RPS14 of the read ~program and determine~ t~e cente~ point
of 2ach segment aB . t~;`unit 5cans~acros~ a~liné. The ~enter
count o~each~egm~t ls utilIzed to~ontrol th- ~ tlcal ~
~; window position of the succeeding ~gm~nt,~ ther~y~providing
a predlctive po~sl~io~; ~or the~nex~"~egmen;t.~
~ Por purpoees~ -o ~load format, th-~line~po3ition analysis
circultry provide5 two signals. ~he ~1r3t signal¦~s~designated
M~QRCD ~mark aenter~d).~;The econd~ign~ LP~Q ~llne po ition
- error). At the end of the line position analysis during format
program step FPS4, the MARKCD signal is high if the system has
detected a mark of at least seven black elements in height and
located within the cen-ter range as determined by the circuits.
Signal LPER indicates one of the following error conditions:
1. Array filled. An array filled condition occurs
if all 38 bits of the blacks enable window
(which is used during load format) are black;
that is, the mark that has been detected is at
least 38 elements high.
2. Double mark. This condition occurs if two marks
at least seven black elements high are detected
within the blacks enable window of 38 elements.
3. Mark high. If the unit detects a mark at least
seven elements in height, but the mark has gone
past or above the centered position, it is
considered a mark high error condition.
During load format a line position analysis is
performed during format program step FPS4. When a mark center
condition is detected, the system progresses to store the
- document advance count in the vertical format data portion of
the memory. The u~it then advances the document twelve steps
(or 0.120 inch). This should advance the mark just detected
out of the array so that it is not detected as a mark high
condition and does not erroneously actuate the LPER signal.
.~ ,
During read program step RPS6, a line position analysis
is performed to determlne where a line of data is with respect
146
- - ;
to the center of the array. During the analysis the "A" register
7001, 7002 reme~bers the least number of white or zero bits
between the top of the array and the mark. The "B" register
7003, 7004 re~embers the least number of whites or zero bits
between the mark and the bottom of the array. The two adders
7021, 7025 perform the difference of "A" - "B" and "B" - "A".
The fine line adjust circuit 7201, 7202, 7209-7213 takes the
posl-tive difference of "A" - "s" or `'B" - "A" and decodes this
difference. The circuit of Figure 72d then recodes this
difference to determine the amount of fine line adjust, or the
; required number of motor steps, to bring the line close to the
center of the array.
When the read program counter advances to step RPS7
the system performs the required fine line adju$t. The fine
line adjust is controlled by three siynals from the line
position analysis circuits. One signal, designated DOWN COU~T,
is used to determine whether the document is to be moved forward
~ or reverse. When D~WN COUNT i5 low, th~sy~tem i~ commanded to
I back up the documsnt. This is done i~ " i positive;
that is, the number of white ~pots below~t~e mark is greater
11 :
,~ ~ than the number of white ~pots above the mark.
A second signal, de~ignated F~, gan~rates pulses at
, i the 960 cycle per second ~tep rate to mcrement~th~ documeat
step motor 500. ~The number o~ pulses gsnerat0d ie in accordance
i 25 with that indicated by the fine line adjust~Fircuitxy in Figure
72d. When the réquired number o~ step~ have be~n eff~cted,
I the system turn~ on a third ~ignal, designat~d-FNAC (fine line
,~ ' ~ ' :
1 1~7
~C~4~1~.7
adjust complete). T~is is the enabling signal for the read
~rogram counter to advance from step RPS7.
In the case where the fine line adjust moves the~'
docu~ent forward, the FNAC signal is turned on i~mediately
~fter th~ last required FNAT advance pulse. In the case where
the document has to be moved back~ard to perform the fine line
ad~u~t, then a six millisecond settling time is initiated
between the last FNAT advance pulse and the FNAC indication.
ThlS time is necessary to allow the motor to settle down, that
is, ~t is required to allow a backward to forward reversal of
the document advance motor 500.
Durinq read program steps RPS6 and RPS10, for six
lines per inch operation, the line position analy~
circultry performs a "line-following" function. As the
syste~ reads during the RPS6 and RPS10 steps, and as soon
as a mark enters shift register 6818 through 6821, a f~rst
'~ segment condition is indicated at flip-flop 6837. ~hi~ triggers
,' r ,
a line position analysis function which determines the position
of that segment with respect to the top of the array. The
~20 center of this first segment is stored in both the fir~t and
moving se~ment registers (6901, 6902) to indicate to the
recognition circuits the desired position of the center of ~he
vercical window for the fifty bits of nabled photo-diode array
and the position of the twenty bits for the recognition enable
window. As the reading progresse~ acros~ th~ d~cu~nt page,
the system trigger~ an additional "mark c~ntered~ analysi~ for
each 0.~ inch segment, or at the end of each field. Th~ re~ult
of each one of these analyse~ i3 stored in moving ~gment
... . ..
14~
~, ' ' , I
-
register 6902. As each segment is analyzed, its center position
with respect to the top of the array replaces the previous
moving segment count held in the register.
The four signals that are sent from the line position
analysis circuitry to the recognition circuit window generator
are FMCK 4, FMCK 8, FMCK 16, FMCK 32. These four bits, derived
from multiplexer 6904, are utilized to provide the count whlcn
represents the center of the segment with respect to the top
of the array.
Assuming that an unrecognized character is detected
during one RPS6 scan and repeat cyFle, the amount of fine
line adjustment must be utilized to modify the output of the
first segment register 6901. This is done to indicate to the
vertical window generator (at the recognition circuits)
approximately where the first segment resides as a result of
the fine line adjust. Upon rescan, a new vertical position of
' the first segment is generated, replacing the previous first
segment register count. This is utilized to predict where the
center will be for the next segment. System operation progresses
to determine the vertical position of each succeeding segment
and to put the center position count into the moving segment
..
register 6902. As the system starts a line, multiplex circuit
6904 first gates out the count of the first segment register
6901 on the FMCK 4 through FMCK 32 lines. After the first
segment position is detected and analyzed, the multiplexer 6904
gates the moving segment register count onto the FMCK lines to
- the vertical window generator at the recognition circuits.
. .
,
I 149
.,,1 .~ . ", " ,, ', ' ,
.. . . . . . .
~4~l47
~, Load Format (YPS4).
As previously described, the page reader circuitry~
generates an LPSR (line position reset) si~nal which goes low
~ during format program step FPS3 and read program steps RPS5 and
i RPS~. This signal serves as a reset for the line position
analysis circuits in preparation for its operation during the
FPS4, RPS6 and RPS10 steps. The LPSR signal resets the various
co~nters and flip-flops and also presets both of the "A" zero
count registers 7001, 7002 and "B" zero count registers 7003,
) 7004 to a count of 48. During load format the system is
forced into a six line per inch operating condition and the
vertical blacks enable window is 38 ~its high; that is, in the
photo-diode array, bits 13 through 50 of the 64 bits are
available. During load format: there is also no "line-following"
procedure followed; the blacks enable window is always at the
bits numbere~ 13 through 50; there is no fine line adjustment
made so that if the unit is in horizontal format mode the load
` format program counter advances the document until there is
an indication that the line is centered. Then, during step
D FPS8, the system scans with the 38-element blacks enable window.
Presumably the characters associated with the horizontal format
fields are centered within the array: if not, they still should
be within the blacks enable window as generated. If for any
reason the characters of the horizontal format fall out~ide the
`5 38-bit blacks enable window, the system generates a read error
flag and effects at least one rescan. There is no fine line
adjustment between the first scan and the rescan. I the
; ' ' .
lS0
- . - _
. .
horiæontal field charac-ters are still not recognizable, the
system generates a format error, rejects the format conditioning
document, and halts operation.
The line position analysis program counter generates
an LPAC (line position analysis complete) signal which goes high
aEter an analysis is completed. Initially the LPAC signal is
forced low when counter 6609 is reset by the LPSR signal; there-
fore, in advancing from FPS3 to FPS4 in the load format program,
; the line position analysis complete signal is low.
~. Load Format - No Mark Detected
In this description it is assumed that there is no
mark in the array and no mark to be detected by the line position
analysis circuits.
C.l (LPS0). LPS0 is the start or home position of
the line position analysis program counter 6609. During this
step it is first determined whether the line position analysis
is complete by detecting at gate 6614 whether signal LPAC is
high. Initially this should not be the case because counter
6609 is reset to all zeros. The system then determines whether
the format program counter is at step FPS4, as detected at gates
6613, 6614O When the ~ormat program counter reaches FPS4 the
,
~ system waits for MUX 63 signal to go high at gate 6614. This
i~ signal synchronizes -the line position analysis circuitry with the
MUXSD serial data coming from the recognition circuit ~uantizer-
multiplexer. When synchronization is obtained, gate 6614
actuates multiplexer 6627 to switch flip-flops 6625. This
¦ in tuFn actuates gate 6626 to provide the LPCT signal which
151
.1
.: . - ~ ,. . .. .
~4~ 7
advances the line position analysis program counter 6609 to
step LPSl.
c.2 (LPSl). The main operation during step LPSl is
the gating of the MUXSD data into the 64-bit shi~t register 6816,
6818-6821, and the enabling of the recirculating gate 6808 to
continue accumulating data into the shift register as long as
the various functions require. During load format the input
ga-te 6814 to the shift register is also gated (gates 6807,
6808) by the 38-bit high blacks enable window. That is, only
bits 13 through 50 of the MUXSD are gated into the shift
register; the other 26 bits are forced into a zero or white
condition. I.PSl also resets the zero counter 6719, 6720. The
system then determines whether the format program count is at
FPS4, via gates 6615, 6616. If not, the system remains at
LPSl. The system is assumed to be at FPS4 and therefore proceeds
to determine whether the MUX63 signal is present at gate 6616.
This signal represents the MUX63 time following that which
`--1
initially enabled the system to advance from LPS0 to LPSl.
;~
The result o~ this timing is that the system remains at LPSl
for one full cycle during which 64 bits of multiplexer serial
data are gated into the registers~ At MUX63 time, counter
6609 advances to LPS2 by the action of gate 6616, multiplQxer
6627, ~lip-flop 6625 and gate 6626.
i~ ~ c.3 (LPS2). The first function performed during step
~ 25 LPS2 is counting (at counter 6719, 6720) the zeros (white bits)
. ~ .
being shifted out of shi~t register 6816. This counts the
l number of white bits starting at the top of the array. Normally
"~
'~ 152
i
, ,. , . . :
.
...
", . ""
, ' .
~049147
the count of whites or zeros continues until the counter reaches
a maximum allowable count of 32, or a mark is detected. Having
assumed there is no mark in the array, the system continues
counting zeros until it reaches the maximum allowable count of
32 which is signified by signal ZR3;2 going low at counter 6720.
During LPS2 the system looks for six zeros in sequence
during the blacks enable window time (bits 13 through 50) to
set flip-flop 6834,which is called a white group or blacks
enable flip-flop. This requires that a white group of six
consecutive bits must be detected at the top of the blacks
enable time before the system is enabled to detect a mark. The
purpose for this relates to the fact that a previous mark centered
condition in load format mode would have triggered the format
load program counter to have advanced the document tw~lve steps
(or 0.12 inch~ before looking for the next mark. An extremely
high mark on the conditioning document, even though it had
i been advanced twelve steps, could still extend down into the
blacks enable portion during the search for the next mark.
By requiring a white group of six consecutive zeros within the
~20 ~ blacks enable window, the lower part of the previous mark is
ignored. Whlte groups flip-flop 6834 is also referred to herein
as the black mark enable flip-flop, although its Q output signal
. ,
~` is designated WHGP throughout the drawings for purposes of
consistency. With the blacks enable flip-flop 6834 set, the
25 system then looks for seven ones (or blacks) in sequence. When
seven ones in sequence are detected at the end of the shift
' :
register 6821 by gates 6825, 6826, SRQ flip-flop 6830 is set.
153
~'
.: . - - . . .
,, :, . .
- , ' ., . ' ' ' ' ,
10~9147
1 ~ In this analysis it i5 assumed that there are not seven ones
in the shift registers; therefore, SRQ flip-flop 6830 is
not set.
During LPS2 the first determination is whether the
zero counter 6719, 6720 has reached the 32 count maximum, as
determined by gates 6721, 6722, 6723. If not, the system
remains at LPS2. It is assumed that the system finally
counts 32 zeros without having the SRQ flip-flop set, there-
fore gate 6620 actuated by the ZR32/44 signal and the program
proceeds to step LPS3.
c.4 (LPS3). During step LPS0 the enable flip-flop
6624 (ENFF) was set. The ENFF signal is utilzed to enable
` the zero counter 6719, 6720 and mark centered counter 6706,
.. j `
6707. Flip-flop 6624 is reset at the next MUX63 time to
stop any further counting and processing of data in the shift
register. The determination made during LPS3 iS whether the
SRQ flip-flop 6830 has been set. This determination is made
at gate 6621. Since it is assumed that there is no mark in
the array, flip-flop 6830 is not set. Gate 6621 then deter-
mines whether it is MUX63 time. At the next MUX63 time flip-
flop 6624 iS reset via gate 6623. The line position analysis
program counter 6609 derives the LPAC (line position analysis
complete) signal high and returns the system to program step
LPSO.
.:; .
` When signal ~PAC is high, the format program counter
can advance, and commands the document to be advanced one step
and then return to FPS4 for another analysis to determine whether
there is a mark in the array. In this manner the format program
;~ ... ~
154
.
~ 9~L~7
1 and line position analysis program interrelate to properly
position the document.
d. Load Format - Mark Detected but Low in the Array.
Assume now that there is a mark to be detected in the
array within the blacks enable window time, but the mark is
below center. At the next FPS4 step the system is enabled to
permit advance from LPSO to LPSI at MUX63 time.
d.l (LPSI). LPSI is maintained for a period from one
MUX63 time to the next, accumulating another 64 bits of data
L0 from the MUXSD line. At MUX63 time the system advances to LPS2.
d.2 (LPS2). During LPS2 counter 6719, 6720 counts ~-
the number of zeros or white spots starting at the top of the
array. It has been assumed that there is a mark in the array
and that it is below center; also assume that during LPS2
counter 6719, 6720 counts 32 zeros before SRQ flip-flop 6830
is set. Therefore, when zero counter 6719, 6720 reaches a
; count of 32, gate 6620 is enabled and the program advances to
LPS3.
d.4(LPS3). The ENFF flip-flop is still set; there-
'0 fore, the system continues to count zeros while looking for a
mark at gate 6824. The SRQ flip-flop 6830 is set when
seven or more bits of black, which constitute the mark, are
" positioned at the end of the shift register 6821. When the
SRO flip-flop 6830 is se-t, gate 6621 is activated and the system
advaces to LPS4.
d.4 (LPS4). The line position analysis program counter
6609, by having advanced to LPS4, indicates that a mark has been
....... , .. ,, .. .... . . ..... . .. . .. ,.. ,.... ~_
- --- - ~
. ' '~ .
. '
. , ''
~4~7
1 detected within the blacks enable window at the array. Therefore
the counter sets flip-flop 6611, which is the mark sensed flip-
flop. Also during LPS4 the contents of the "A" zero register
7001, 7002, are compared with the count in the zero counter 6719,
6720 at comparator 7011. During LPSR time the "A" register 7001,
7002, and "B" register 7003, 7004 had both been preset to a count
of 48. During LPS 3 the zero counter 6719, 6720 was stopped
when it reached a count of 32; therefore, the zero counter
count is less than the count in the "A" register. The A >B
output signal from comparator 7011 actuates gate 7017
and flip~flop 7018 which in turn triggers gate 6716 to provide
the æRAT signal. This signal clocks the new zero count into
"A" register 7001, 7002. After the new count has been transferred
to the "A" register, counter 6719, 6720 is reset at timing pulse
; TP~ and the counter is enabled to count zeros below the mark.
If MUX 63 time occurs during LPS4 it resets ENFF flip-flop
6624 via gate 6623. If MUX63 has not occurred yet, the system
remains at LPS4 for only a two microsecond duration. corresponding
to one phase of the six phase clock master timer circuit. The
unit is then advanced to LPS5 at timing pulse TPE.
d.5 (LPS5). The SRQ flip-flop 6830 is reset when four
zeros or white bits are detected at the last four positions
of the shift register by gates 6825, 6826. When the four zeros
occur and reset the SRQ flip-flop, gates 6710, 6713 permit
counter 6719, 6720 to count the zeros below the mark in the
array. The zero counter again is prevented from counting past
32 by gates 6721-6723 and 6713. If MUX63 occurs during LPS5,
- ... ... --.. ... ... .. ~_
- ..... ,, ~
:~ - - .- . .,
~
, , ' ,
156
'', ' ~
:' . ~ . .
'
'' ', .. ~ , . , '
:.: , , : . .
- :. . ..
919~7
1 flip-flop 6624 is reset. The determination made during LPS5 iS
whether flip-flop 6624 is reset. It is in fact reset at MUX63
time, after which the system has completed analyzing the 64 bits
in the shift register. Counter 6609 is then advanced to step
LPS6.
d.6 (LPS6). During step LPS6 the contents of "B" zero
register 7003,7004 are compared with the count in zero counter
6719,6720. If the zero counter contents are less than the "B"
register contents, the new count is transferred from counter
6719, 6720 to "B" registers 7003, 7004by signal ZRBT via gate
7016, 7017, flip-flop 7018 and gate 6017. During LPS6 the input
and recirculating gates 6814, 6808 of the shift register are
enabledto start accumulating the MUXSD data for the next
analysis. The unit remains at LPS6 for only a two microsecond
period associated with one phase of the six phase master timing
clock. The unit then advances to LPS7.
` d.7 (LPS7). During LPS7 the input and recirculation -
gates 6814, 6808 of the shift register are enabl~ to permit
accumulation of data for the next analysis. The LPS7 count
. ~ ~
at counter 6609 also actuates the LPAC (line positon analysis
; complete) signal and advances to return the counter to LPSO
aftera two microsecond period.
e. '_" and "B" Zero Re~ister - Mark Positon Indicator
~, The zero counter 6719, 6720 is a six bit synchronous ~ -
counter. The "A" and "B" registers 7001, 7002 and 7003, 7004
are five-bit registers so that the "A" and "B" registers hold
only the five high order bits of the zero count, the lowest
, . .. .. ...
157
. ~ :'"' ' ' ''' '
..
: :
~49~7
1 order bit of the æero counter being dropped. The line position
analysis circuity includes two adders 7021, 7025. Adder 7021
provides the difference of the "A" register contents minus the
"B'7 register contents. Adder 7025 provides the difference of
the "B" register contents minus the "A" register contents. The
outputs of these two adders are analyzed in the circuits of
Figure 71a to determine whether a mark is near the center of the
array. is high in the array, or is low in the array. A mark
centered condition is indicated if a mark is detected when no
array-filled condition is determined and the output of the two
adders is such that "A" minus "B" and "B" minus "A" are equal to
or less than three. A mark low condition is indicated if "A"
minus "B" is equal to or greater than four. A mark high condition
is indicated if "B" minus "A" is equal to or greater than four.
For the present analysis it is assumed that a mark is detected
but is low in the array. This is indicated by addex 7205
showing that "B" minus "A" is equal to or greater than four.
Each document motor advance step moves the document
0.0104 inch. Each array photocell element equivalent height
at the document is 0.005875 inch. Therefore, each motor step
advances the document to approximately two elements. After a
document advances one step, or two elements, on the next position
analysis, "A" register 7001,7002 has a count of two less
and the "B" register 7003,7004 has a count of two more than
in the previous analysis. Therefore, moving the document one
step changes the result of "A" minus "s" and "B" minus "A"
by a total count difference of four. If then "A" minus "B" is
. ~
. -
158
'`:
.
. . : . .
,: ' " ',, , ,:
:, .,, , . : . :
, . . - . . , . . . : . .
, : , - : . :: :
/ ~
~ ~g~a~7
e~ual to or greater than four, the document should be moved one
more step. If "A" minus "B" is less than four, one more step
moves the mark past the center of the array. - >
f. Load Format - Mark Detected and Centered
j During load format, the line position analysis circuits
eventually detect a mark which is near the center of the array~
A mark centered is defined as a condition where a mark is
detected and "A" minus "B" is less than four, and "B" minus "A"
is less than 4. The operation of the line position analysis
) circuits is the same regardless of the detected mark having
been centered or low. The contents of the "A" and "B" registers
e~fect the load format program counter only. That is, after
performing a line position analysis in step FPS4, the format
program advances to FPS5 and determines whether the m~rk is
centered. If not, the determination is made whether the mark
was high or the array was filled. If the answer is still no
the format program advances to FPSll and advances the document
- one more step. If the mark were in fact centered, then the
~ormat program counter is advanced from FPS5 to FPS6 to generate
0 a memory write cycle, whereby the document advance count is
- stored in vertical format portion of the memory.
g- Line Position Error
After performing the line position analysis during
' step FPS4 of the format program, the format program counter
'5 advances to step FPS5. During FPS5 the system tests to see
if there is a line position error. If there is a line position
error the mark centered condition lS inhibited at gates 7101
159
.
through 7107 and 710~, and a Eormat error is indicated in the
format control circuits which return the format program counter
to step FPS0. The following conditions are defined as a line
position error (LPER) during load format:
1. Array filled. An array filled condition occurs
if all 38 bits of the blacks enable window are black; that is,
the detected black mark is at least 38 elements high.
2. Double mark. This condition occurs if two marks,
each at least seven black elements high, are detected within the
black enable window of 38 elements.
; 3. Mark high. If the unit detects a mark of at least
; seven elements in height, but the mark has gone past tabove) the
center position, a mark high condition exists. A mark high condi-
tion is considered an error. This is indicated by the output of
the "B" minus I~A~I adder 7025 being equal to or greater than four.
h. Read Mode - Llne Position Analysis Durin~ RPS6 and RPSl0
Signal LPSR (line position reset) is generated during
read program steps RPS5 and RPS9, the steps preceding RPS6 and
RPS10. One of the functions of LPSR is to preset each of the
~ 20 "A" and "B" zero registers 7001, 7002 and 7003, 7004 to a count
,~ of 48. The "A" and "B" registers are the registers which hold
the minimum zero count above and below the mark as the system
scans across the line. During operation at six lines per inch,
the "line-following" function is performed for the vertical
blacks enable window. For this purpose an additional preset
is furnlshed during steps RPS3 and RPSl3 of the read program to
, preset the first and moving segment center count registers 6901,
.i
1 160
. ' .
. ' ': ,' ~ ' ' , ' '
1~49~7
6902 to 32. That is, these reset times are utilized to preset
the count of 32 which is used as a center count of 64 bit MUX
serial data.
For the present analysis assume that the system is
in vertical format only (i.e. not operating with horizontal
format) and it is operating at three rather than six lines per
inch. The analysis com~ences at LPS0.
h~ 1 (LPSO) . The first determination during LPSO is
whether the line position analysis is complete (signal LPAC,
ga-te 6614). The answer under the assumed conditions is no. The
next determination is whether the system is in read program steps
RPS6 or RPS10 and whether the scan duration signal has been turned
on (gate 6612). Assuming that this is the case, the determination
is next made as to whether it is MUX63 time (gate 661~). That is,
are the line position analysis circuits synchronized with the MUX
serial data (MUXSD) counter at the recognition centers? When
M~X63 time occurs, the system advances to LPSl by actuating gate
. :
6614.
1 ~ ..
j~ h~2 (LPSl). The main function during LPSl is to
;~
i 20 accumulate MUXSD (data) in the shift register 6816, 6818-6821.
Therefore, LPSl is one of the enabling signals to the input and
recirculating gates (6809, 6814) of the shift register. MUXSD
is gated to the 64 bit sbift register during LPSl when the
. ~
BLACK EN signal lS high. For three lines pex inch operation the
~lacks enable window is on for the full 64 bit data. LPSl also
reset:s the zero counter 6719, 6720 and sets the ENE'F flip-flop
, 6624" The first determination during LPSl is whether the system
.1
1 161
is in horizontal fornat (gates 6617) . The answer under the
assumed con~itions is no. The next determination is whether the
system is operating at six lines per inch (6836, flip-flop 6837,
gates 6838, 6618). The answer is again no under the assumed
conditions. Therefore the system loops around and determines
whether -the system has scanned a segment of 128 counts (gate
6618). The meaning of this is described in the following
paragraph.
The scan coun-ter counts at a rate of 145 counts per
inch as the unit scans across the page; that is, one count for
every MU~63 signal. A count of 128 counts is a scan of approxi-
mately 0.8 inch. Therefore, a line position analysis is effected
after accumulating MtlXSD for a segment of approximately 0.8 inch
(128 cyc:les of MUXSD). When the scan counter has generated a
signal SC128, the LPSl advance Elip-flop 6619 is set. The
determination is then made whether it is MUX63 time (gate 6616).
When the next M~J~63 signal appears the line position analysis
program advances to LPS2.
h.3 (LPS2) . The LPS2 step is utilized to count zeros
' 20 or whites into the mark centered counter 6706, 6707. The
-; determination of the center of the mark with respect to the top
of the array is performed during LPS2, LPS3, LPS4 and LPS5,
regardless of whether the system is in three or six lines per
inch operation. The results of the determination are only
utilized if the system is actually operating in six lines per
`
inch mode. For the purpose of the mark centered counter 6706,
6707, the system counts zeros ~whites) during LPS2 and LPS3
162
91~7 ::
1 and half the number of ones (blacks) of a mark during LPS2,
LPS3, LPS4 and LPS5. This operation yields the center postion
of the mark with respect to the top of the array. Therefore,
LPS2 is one of the enabling signals to the counting of the
zeros and half of the ones into the mark centered counter.
During LPS2 counter 6719, 6720 counts zeros (white
bits) out of the shift register, starting at the top of the
array and continuing until reaching a maximum count of 44. That
is, if no mark is detected, zero counter 6719, 6720 counts until
it reaches a count of 44, after which gates 6723 and 6713 are
`~ actuated to inhibit further countings. If the system were
operating in the six line per inch mode, zero counter 6719,
6720 would stop counting at a count of 32. Starting with LPS2
the system looks for a mark of at least 17 ones (or black bits)
in sequence in the shift registers. The last 32 bits of the
shift register have parallel outputs which feed decoding gates
6822, 6823,6824. When the last 17 bits of the shift register
are all ones, indicating a black mark at least 17 ones in
length at the end of the shift register, SRQ flip-flop 6830
is set. If there is a mark in theshift register it may be
sensed either during LPS2 or LPS3. The SRQ flip-flop is reset
when gates 6825, 6826 detect four zeros (or whites) appearing
at the last Iour stages of the shift register. The question
is then asked (during LPS2): Has the unit counted ma~imum
: .,
`- number of zeros? (gate 6620). For three l1nes per inch
operation this number is 4~. Assuming that the answer is yes
the system advances to LPS3. -
- - . :
1, , ' ' ' ' '" '~
3Q
163
.~ " .
:, .
- , ~ .
, ,, . ',. ' .
~ . . . . ., . . :
.. . . .
;~ ' ~ ' , . ', "' . ' ' ' ' . ' ' ' '
9:~L4~
h.4 (LPS3) . During LPS3, gate 6623 is enabled to
permit reset of the ENFF flip-flop 6624 at MUX63 time. The
system also continues to count any ones into the mark centered
counter 6706, 6707. Note that the number of ones entering
counter 6706, 6707 is divided by two, by means of flip-flop
6703, before entering the counter. The determination is then
made whether the SRQ flip-flop 6830 is set (gate 6621). Assume
for the present that no mark has been accumulated in the shift
register; therefore, the answer is no. If it is not MUX63 time,
(gate 6621) the system stays at step LPS3 until MUX63 time
resets the enable flip-flop 6624. The system then determines
if the scan duration has terminated (gate 6601) or i~ a black
field has been detected by flip-flop 6839 (gate 6602). If not,
the system returns to LPS0.
The foregoing description has illustrated the
accumulation of 128 cycles of MUXSD into the shift register,
followed by an analysis of the contents of the shift register
with the result that no mark was found. Upon returning to
LPS0 the system detects that signal LPA~ is high ~at gate 6614)
indicating that a llne position analysis has not been completed.
The read program is still in step~RPS6 or 10, and the scan
:. .
duration is still active. At the next MUX63 time, the system
advances to LPSl in the line position analysis program.
; ~ h.5 (LPSl). Assume the same sequence of operation
, .
l 25 during step LPSl as described in section h.2 above. The
:' .
i system is not in horlzontal format and is not operating at
six lines per inch. Consequently, the system awaits a scan
:~ :
!~ 164
.
'
count of 128 (at gate 6618) or the end of a scan duration (at
gates 6601 and 6612). Assume that the system is now in the
mids-t of a second segment of 128 scan counts proceeding across
the line. When the SC128 signal is received at gate 6618, it
sets the LPSl advance flip-flop 6619. At the next MUX63 time
the system advances to LPS2.
h.6 (LPS2). Assume the same conditions considered
in h.3 above except that in this case assume there is a mark
which occupies a portion of shift registers 6618-6821 close to
the center of the array. Under these circumstances, the mark
is detected and the SRQ flip-flop 6830 is set before zero
counter 6719, 6720 reaches a count of 44. Gate 6620 detects
this situation and advances the line position analysis program
to LPS3.
h.7 (LPS3). If MUX63 time occurs during LPS3,
enable flip-flop 6624 is reset. Assuming that MUX63 has not
yet occurred, the system continues to count ones,divided by
two, into the mark centere~ counter 6706, 6707. Gate 6621
then determines whether the SRQ flip-flop 6830 has been set;
since it has, the line position analysis program is advanced
to LPS4. In this situation the time duration of the LPS3
step is two microseconds; that is, one cycle of the six phase
.
master timing clock.
h.8 (LPS4). During LPS4 the mark centered counter
6706, 6707 continues to count half the number of ones in the
. ~ ,
detected mark. Having detected a mark as indicated by the
SRQ flip-flop 6830 being set, the system now sets the mark
, .
165
,~
, ~ .
' , .
9~4~
flip-flop 6611 by advancing to step LPS4. SRQ flip-flop 6830
is reset when four consecutive zeros (or whites) are detected
in sequence at the last four stages of shift register 6821.
During LPS4 the system compares the contents of "A" zero
register 7001, 7002 with the count in the zero counter 6719,
6720 at comparator 7011. If the count in the zero counter is
less than the contents of the "A" register, the new zero count
is placed in the "A" register ~y the ZRAT signal derived at
gate 6716 by the action of gate 7017 and flip-flop 7018. Zero
counter 6719, 6720 is then reset at the next TPD pulse so that
it may count the number of zeros below the detected mark. If
MUX63 time occurs during LPS4, ENFF flip-flop 6624 is reset.
LPS4 duration is two microseconds, the time for one phase
of the master clock. The system then advances to step
LPS5.
h.9 (LPS5). During LPS5 the mark centered counter
6706, 6707 continues to count half of the ones in the de-tected
mark if the mark is still at the end of the shift registerS
Once again the SRQ flip-flop 6830 is reset if four zeros in
sequence appear at the end of shift register 6821. During
LPS5 the system counts the number of zeros below the mark, but
not to exceed a count of 44 during three lines per inch operation
or a count of 32 during six lines per inch operation. When MUX63
time occurs it resets ENFF Elip-flop 6624 and advances~the
25~ ~ line position analysis program to step LPS6.
; h.10 (LPS6). During LPS6 the "B" zero register 7003,
7004 has its contents compared with the count in zero counter
166
~ .
~:. . , ~ ! ' ' ' ' ' ' '
1~49~7
6719, 6720 at comparator 7011. If the zero counter count is
less than the "B" register contents, the new count is placed
in the "B" register by means of signal ZRBT derived at the gate
6717 by the action of gate 7017 and flip-flop 7018. Step LPS6
also enables the input and recirculation gate 6814 of the shift
register. The count in mark centered counter 6706, 6707 is
placed in the moving segment register 6921 during LPS6 by the
M SEG GT signal generated by gate 6929. If this detected mark
is the first mark detected on the line being scanned, the
contents of counter 6706, 6707 is also placed in the first
segment register 6901 by the F SEG GT signal generated at gate
; 6928. The function of the moving segment register relates to the
"line-following" operation which is discussed in greater detail
subsequently. Step LPS6 remains in force for a duration of
two microseconds after which the program advances to LPS7.
h.ll (LPS7) . During step LPS7 the input and
recirculation gate 6814 for the shift register remains enabled
to permit accumulation of data for the next analysis. The
determination is made whether the scan duration has terminated
(gate 6601) or a black field has been detected ~gate 6602).
Assuming the answer to be no, the system returns to LPS0 where
it determines whether or not a line position anal~sis has
been completed. If the answer is no, and the system is in either
the RPS6 or RPS10 steps of the read ~rogram, and the scan
duration is still in force, gates 6612, 6613 and 6614 cooperate
to advance the program to step LPSl at the next MUX63 time.
~,
167
h.l2 (LPSl). Assume that the previously described
analysis has been repeated for a number of SC128 count pulsès
il and that the system is approaching the end of the scan line
during which it has accumulated a smaller numbèr of MUXSD into
the shift register. The determination is then made whether or
not the unit has reached the end of the scan duration during
steps RPS6 or RPSlO. If so, flip-flop 6619 is set, activating
gate 6615 to prime gate 6616 so that at the next MUX63 time
the program advances to step LPS2.
h.l3 (LPS2). As described previously in relation to
step LPS2, the program advances to LPS3 if the maximum number
of zeros have been counted or the SRQ flip-flop 6830 has been
set. Assume that the unit does in fact advance to LPS3.
h.l4 (LPS3). Now assume that the SRQ flip-flop 6830
has not been set. At the next MUX63 time, the ENFF flip-flop
~ 6624 is reset. The determination is then made,at gates 6601,
i~ 6602, if the scan duration is completed or a black field has
been detected. Since it has been assumed that it is the end
;; of a scan duration, gate 6602 activates gate 6604 which in turn
activates gate 6606 to set the highest order stage of counter
6609. As a consequence the LPAC signal goes high and the LPAC
signal goes low to~return the counter to LPS0. With LPAC low,
gate 6614 maintains the program at LPS0 until there is further
operation of the read program.
25 ~ Now assume, during the LPS3 step, that the SRQ flip-
flop was set. The system then automatically advances from LPS3
to LPS4 by the actlon of gate 6621.
'' , ; '
168
.
. ---, . . . . . . .
:- ' ~' '
~CI 49~47
-- h.l5 (LP~;4). The operation during step LPS4 progresses
as described above in h.8. The unit remains in LPS4 for a two
microsecond durati~n and then advances to LPS5.
h.l6 (LPS5) . The system remains in LPS5 until the
next l~1U~63 time and performs the operations described in paragraph
h.9. When flLp-flop 6624 is reset, the program advances to LPS6.
h.l7 (LPS6) . During LPS6 the system performs the
functions described in paragraph h.10. The program remains at
LPS6 for a period of two microseconds and then advances to LPS7.
-
h.l8 (LPS7). The determination made during LPS7 iswhether the end of scan duration has occurred or a black field
has been detected (gates 6601, 6602) ., It has been assumed that
the scan duration has terminated; therefore gate 6602 actuates
gate 6604 tO in turn actuate gate 6608. The latter gate provides
the ADJCSL signal which is applied to the load terminal of the
step counter 7221 to permit entry of the fine line count (i.e.
.
the required line position correction step number) into counter
7221. In addition the line position analysis complete signal is
actuated at this time and the line posltion analysis program
returns to step LPS0.
The foregoing description has illustrated the process
of scanning across a line of data during the RPS6 and RPS10
read program steps. There are also two counts of zeros (whites)
stored in the "A" and "B" registers. Register "A" contains the
minimum number of zeros or white spots from the top of the array
to the top of thè mark. The "B" register contains the minimum
number of zeros from the bottom of the mark to the bottom of the
169
', ' ': " . '. ' " ,' ' '
9~
~rray. The contents of the "A" and "s" registeris are maintained
until the next LPSR signal is received by the line position
analysis circuitry. The contents of the "A" and "B" registers
I are now utilized for any required fine line adjustment. If the
i previous reading ~nd analysis had been effected during step RPS6
of the read program, the next step of the read program counter is
RPS7. RPS7 is the read program step during which any required
fine line adjustment is performed. ~;
i, Fine Line Adjust - Read Mode (RPS7)
No fine line adjustment is performed after a read
and scan operation during an RPS10 step. However, the "line-
following" function data, utilized during six lines per inch
operation, is utilized during RPS10.
The contents of the "A" register 7001~ 7002 and the
i "B" register 7003, 7004 are applied to adders 7021 and 7025.
The carry signal from the "B" minus "A" adders 7025 is
. . . .
designated B ~ A. This signal is high if "B" minus "A"
results in a positive number, and the signal is utilized to
control the selector input of multiplexer 7201. If the signal
~1 B ~ A is low, the output of the "A" minus "B" adders 7021 is
selected at multiplexer 7201 as the input to the four bit to
~ sixteen line decoder 7202. If the signal B ~ A is high, the
,-~` output of adder 7025 is selected as the input to decoder 7202.
Table Ll, in the first column, indicates the possible results
of "A" minus "B" operation. This column should also be read
as "B" minus "A" for the case where the "B" minus "A" result
is positive.
'
~ 170
: .
The sixteen line output from decoder 7202 is identified
as "A" minus "B" in the second column of table Ll. The column
identified as "A2" minus "B2" is actually the "A" minus "B"
count divided by two. As previously explained, when a document
is moved in a forward direction, the number of steps moved is
subtracted from the "~" count and added to the "B" count. There-
fore, the effect of moving the document is to change the
difference of "A" minus "B" by twice the amount. Therefore,
in calculating the required amount of movement for a document,
take "A" minus "B" and divide by two; then place in the first
column of table L1 to obtain the desired result. For example,
in the A2 minus B2 column, consider the row designated 12-13.
~he actual difference in the "A" and "B" count is 24 to 26.
The 12-13 is the actual dlfference divided by two. In the
i second column, designated DI~, the ni~meral 5 indicates that the
decoder 7202 has decoded this difference (12-13) as 6~ The
; third column then Indicates that the number of motor steps
required for adjustment is 7. The calculations for verifying
this operation are as follows: (a) each motor step moves the
document 0.0104 inch; (b) seven steps of the motor advances a
.... .
document 0.0728 inch. Each vertical element viewed by the array
is 0.005875 inch. Therefore, dividing the 0.072~ by 0.005~75
provides a result of 12.4 elements. The required movement, as
indicated by the first column, was 12-13 elements. Therefore,
5~ this is the closest approximation that can be made to bring the
line close to the center of the array.
171
,: :
. , - .
' ', ::', . , , . ' ': . :
, : ,: ............... ' , ' :
4~47
The output signals from decoder 7202 are designated
DIF0 t~rough DIF12, and are applied to four decoder gates 7210-
7213. These gates generate a TWOS complement to preset the
motor step counter 7221. Continuing with the previously
considered example of "A" minus "B" at 12-13, it is noted that
. .
the counter is preset to the binary equivalent of 9. When the
read program advances to RPS7 to enable the fine line adjust
function, document advance step pulses (FNAT) are generated to
activate step motor 500 and advance the document. Referring
to Table Ll again, it is noted that seven motor steps are
required to advance the document advance counter to a count of
zero which indicates that the fine line adjustment is completed
(FNAC). When a count of zero is reached at counter 7221, further
FNAT pulses are inhibited at gate 7228. If the fine llne
adjustment involves a backward movement of the document, the
signal B ~ A actuates gate 7218 to provide the DOWN COUNT
signal which instructs step motor 500 to step bac~ward. After
the motor step counter 7221 reaches a zero count further
generation of the FNAT pulses are inhibited at gate 7228.
In addition the continuing advance of counter 7221 is permitted
until a count of six is reached, at which time the FNAC signal
is generated with the aid of gates 7225, 7226, 7229, 7215.
These additional six counts introduce an approximately six
milIisecond delay before the motor can be reversed or changed
i from a reverse to forward direction.
j. Line-Follower Function
During six lines per inch operation the blac~s enable
vertical window, which gates data into the shi~t register, is
172
. , . . , , . :
' , ,, , ''.'~ ' ,'. .' '. '.. ,. ', , . ~, ,,
50 bits high. In the recognition circuitry a second vertical
window, 20 elements in height, is generated to enable the
recognition circuits. The "line-following" circuitry of the
I line position analysis circuits moves these two windows up and
down in synchronis~ to follow any detected skew or vertical
mis-registration of the line. This function is perfor~ed both
during the RPS6 and RPS10 steps of the read program. During
LPSl gate 6701 detects the very first mark indication in the
shift register. When such a mark, of 17 bits or greater length,
!0 is detected, the system performs its first analysis. As a
result of this analysis the mark centered counter 6706, 6707
contains a count representing the center position of the mark
with respect to the top of the array. This mar~ centered
counter lS placed into the first segment register 6901 and into
LS moving segment register 6921. Multiplexer 6904 selects the
output of the moving segment register and gates this to the
recognition oircuits window generator. As ~he system progresses
across the document ln reading a line, and a line position
~ analysis is made of each 0.8 inch segment or horizontal
field segment, the new mark centered count is placed into
-~ moving segment register 6921. In this manner the center
position of each segment is utilized to control the position
of the black enable windows for the next segment.
After completing the first RPS6 ~can and proceeding
.25 to step RPS7 to perform a fine line adjustment, the amount o~
fine line adjustment is stor~d in another regi~ter 6902. When
starting to read during a second RPS6 step, if a re~can i~
, ,.~, ` .
" ' , ' ' ,
: .: .:- , . - . . ,
' ~ ' :" ' ' ' ' ' :
::, ' ', : ' :
;
~049:~ ~7
required at the same line, the amount of fine line adjustment
is utilized to modify the count stored for the first segmentO
The modified count is now gated by multiplexer 6904 to the
recognition circuitry where the first segment should be within
the arrav as a result of a fine line adjustment. On rescan
then, the first segment is detected again, resulting in a new
count stored in the mark centered counter 6706, 6707. This
new count, on the rescan for the first segment, is now stored
in the first segment register 6901 and moving segment register
6921; the selection is then set at multiplexer 6904 so that the
output of the new count in the moving segment register is
transferred to the recognition circuits vertical window
generator. The scanning and modification of the moving segment
register continues as the system contlnues reading across the
`5 llne. If during the fir~. RPS6 rescan there is still another
unrecognized character in the line, the system proceeds to
perform another fine line adjustment during the next RPS7.
trhls might require a movement of the paper and storing of
the required fine line adjustment count in register 6902.
0~ This stored count provides the predictive position for the
first segment of the first RPS10 rescan. During the RPS10
rescan a first segment is detected, its mark centered position
is determined, and this new count is now placed into the first
segment register 6901 and moving segment register 6921. As
the system continues to read in the RPS10 step of the read program, -
the vertical position of each segment is determined and the
contents of moving segment register 6921 are modified and
' . ~' .
174
.'`',
' ' , ;
,~: . .', , , . ,. ' . ~ ,' ' ' ', ' ~
9~9~7
TABLE Ll
FINE LINE ADJUST
ADJUST MOTOR STEP COUNTER (FNAT)
_ _
~ OF COUNTER PRESET & OUTPUT
A2-B2 DIF MOTOR .
. . STEPS DD/QD DC/QC DB/QB D~/Q~
24-25 12 11 0 1 0
22-23 11 11 . 0 1 0
20-21 10 11 0 1 0
18-19 9 10 0 1 1 0
16-17 8 9 0 1 1
1~-15 7 8 1 0 0 0
12-13 6 7 1 0 0
10-11 5 6 1 0 1 0
8-9 4 5 1 0 1
6-7 3 4 1 1 0 0
4-5 2 3 1 1 0 1
: 2 1 1 1 0
~2-3 1 1 ~ . 0 0 1 0
FOR B>A, MOTOR STEPS0 0 l
.~ IN REVERSE DIRECTIONO O 1 O
MUST ALLOW MOTOR 0 0 1
SETTLINE TIME BEFORE
TRYING TO GO FO~WARDO 1 O l
ON NEXT LINE 0 1 1 0
O I O I O O 1 1 O
'; :
FNAT - FINE LINE ADJUST PULSES TO MOTOR .
~l~ FNAC ~ FINE LINE ADJUS~ COMPLETE
i`~
~ (A ~ B)-(B ~ A) = (A = B) LINE CENTERED, NO ADJ.
'i ~ .
! 1~ - ~
.
.~ .
l ` ~ :
,~
1 175
~1
!
.
4~
gated to the recognition circuit window generator. After the
first RPSlO rescan, if any additional rescans are required
there is no fine line adjustment performed. Therefore, the
conten~ of the fine line adjust register 6902 are reset to zero
so that the first segment vertical count is no longer modified
at adder 6903 during subsequent RPS10 rescans. As each RPSlO
rescan commences, and a first segment is detected, its vertical
center count is placed into the first segment register 6901
and the moving segment register 6921. Thereafter the contents
of the first segment register and moving segment register are
multiplexed by multiplexer 6904 to the vertical window
generators to move the blacks enable window and recognition
windows accordingly.
This "line-following" function, during six lines per
inch operation, provides for a gross amount of skew of the line
on the document. The line could in fact extend for the full
sixty elements of the array. There is a requirement, however,
that this be a progressive skew of the line across the document
~ ~ and not a zig-zag or jump skew. That is, it is still necessary
-l; 20 that the vertical misregistration of adjacent characters, or
!¦ ~
characters within the segment, ~e restricted as compared to the
,l wide latitude allowed the three lines per inch operation.
;l
III(B) RECOGNITION CIRCUITRY
~ ; The R~cognition Circuitry is 1llustrated in Figures
: 25 89-124 and serves mainly to receive and identi~y charact~r signalsfrom the photodiode array. In addition, the~e circuits provide
varlous control and timing signals reguired to facilitate
recognition of charasters and the proce~sing of characters in
l the Control Logic circuits.
,~,
1~ 176
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~49~7
III(B.l) QUANTIZER MULTIPLEXER CIRCUITS
I'he quantizer multiplexer circuits are illustrated
in Figures 89-91 of the accompanying drawings~ The sixty
signals (channels 1-60) from the photo-diode array are applied
to respective preamplifiers 8901-8960. Each amplified channel
signal is then stored in a respective bit in registers 8961-
8975. The amplifiers 8901-8960 are illustrated in detail in
Figure 91 by representative amplifiers 8901 and 8960. Each
channel signal is fed through a potentiometer which serves as
a gain adjustment which assures tha-t the signal applied to the
registers is at approximately the same amplitude all across the
array. The output signal from the potentiometer is fed through
a low pass RC filter to the non-inverting input terminal (~)
of a voltage comparator operational amplifier. The inverting
15 ~ input terminal (-) of the voltage comparator is fed from a
threshold adjust voltage bus derived from amplifiers 9101, 9102,
and which is common to all sixty amplifiers. The output
signals from the photo-diode array are phased such that a
character segment or black detected at the array provides a
negative signal. Since these negative signals are fed to the
non-inverting input terminals of the channel amplifiers, a
` detected black appears as a low or close to zero voltage (logic
zero) at registers 8961-8975.
Registers 8961-8975 simply constitute RS latches whose
,25 enable input terminals are maintained at ground. The sample
signal, derived from amplifier 9010, is fed to the reset input
.
terminals of all of the latches. When this sample signal is
177
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raised to binary l, the latches are able to receive and store
the channel signals. At any time during the sampIe period, the
low on the respective channel signal line produces a high level
signal at the Q output terminal of the latch. This Q signal
remains high until the sample signal once again goes low. At
load time the signals from the latches are transferred into
parallel-load shift registers 8976-8983. The two uppermost
input signal~ terminals at shift register 8976 and the two
lowermost input signa~ terminals at shift register 8983 are
continuously maintained at low signal level (ground) in order
to provide two blank bits at the beginning and end of each
received data slice. This is done merely for convenience
because it was found simpler to utilize a 64 pulae shift`cycle
rather than a 60 pulse shift cycle, yet only sixty channels of
data are received. Thus the data received on the channel l
signal line lS actually placed in the third bit from the start
of the data slice which is to be shifted serially out of the
interconnected chain of shift registers 8976-8983.
Referring for a moment to Figure 90, flip-flops 9003
and 9004 are JK fLip-flops interconnected as a divide-by-four
counter utilizing timing pulse TPF as a clock input signal.
The carry output signals of these flip-flops are connected through
NAND gate 9006 and inverter 9007 to the ENT~input terminal of
counter 9008. Counter 9008 is a divide-by-sixteen counter, which
when combined with the divide-by-four counter (flip-flops 9003,
9004) provides an overall d1vision factor of 64. The carry
output signal from counter 9008 is designated MUX63. The timing
178
.
1~49~ 7
of this signal is illustrated in Figure 49 relative to the master
six phase timing sequence. The sixteen and thirty-two weight
output signals from counter 9008 are coupled through ~AND gate
9009 and inverter 9010 to provide the sample signal utilized to
enter data into shift registers 8961-8975. The sample signal is
high during counts 48 through 63 of the counter in Figure 90 and
is utilized to permit any ~lac~ detected by a photo-diode at the
array during this interval to be stored as a corresponding binary
1 signal at the appropriate shift register bit. As mentioned
previously, -this binary 1 or high output signal from the shift
register remains so stored until the end of the sample interval
(MUX count 63) whether or not a black is still being detected
at the corresponding photo-diode in the array. Upon occurrence
of timing pulse TPD during the MUX63 interval, the LQAD signal
goes low (as illustrated in timing diagram Figure 49) causing
the data stored in registers 8961-8975 to be transferred into
shift registers 8976-8983. The detected vertical character
slice is thus located in the serially inter-connected shift
~ ~ registers where it awaits serial shifting so that it may be
; 20 integrated with additional detected slices for purposes of
recognition.
,
! The MUX CLK signal, generated at gate 9202, coincideswith timing pulse TPA during all but the sixty-fourth count
interval for the counter in figure 90 (reference timing diagram
Figure 49). The MUX CLK pulses act through inverter 8984
to serially shift data through shift register chain 8976-8983
by one step during all but the sixty-fourth count interval for
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the counter of Figure 90; it is during this interval that the
LOAD pulse permits entry of data into the shift registers.
Actual shifting in the shift register chain occurs at the
leading edge of the MUX CLK pulses.
All of the binary outputs of the sixty-four bit
counter of Figure 90 are brought out for use in other portions
of the recognition circuitry to perform various timing functions
during the MUX or vertical scan interval. These output signals
are labeled MUX A through MUX F and MUX A.
Amplifiers 9101 and 9102 are two halves of dual
operation amplifier utilized for purposes of threshold control
at the individual channel amplifiers 8901-8960. Amplifier 9101
is utilized as a summing amplifier to which the various output
signals from threshold adjustment potentiometers are fed. The
output voltage from amplifier stage 9101 is proportional to the
sum of the currents flowing through the summation resistors
connected to the inverting input terminal of that amplifier.
Each of the summing resistors receives itS current through
`appropriate transistor switches 9103 through 9110. If the
switch for a particular summing resistor is off the current
through that resistor is zero and therefore the effect oE that
particular summing resistor is nil. Amplifier stage 9102 is
an inverting amplifier which drives the reference input terminals
to all of the channel amplifiers 8901 through 8960 via a common
` 25 bus. In the handwritten mode the signal HWGC signal, derived
s from inverter 12005, is low and transistor switch 9103 is
s rendered conductive. The collector of this transistor rises
180
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to the positive supply voltage level and conducts current through
the adjustment pot connected to the HWG line. Control of this
pot determines the effect of the HWG line at sum~ing amplifier
9101. Operation of the other adjustment controls is similar
with the exception that the T~l and THD2 lines are connected -to
a negative supply voltage and cause a negative current to flow
through their associated summing resistors, thereby serving to
reduce the threshold voltage at summing amplifier 9101. The
; 07B line is utilized in conjunction with the 7B mode whereas the
T~Dl through THD4 lines are utilized in conjunction with re-scan
and permit the threshold to be changed accordingly if re-scan of
a line is required due to lack of recognition of a character
during the first or subsequent scans.
The quantized serial data, designated by signal MUX SD,
is shifted out of the shift register chain 8976-8983 from
register 8983, in the same order as the channel numbers from
which the data was originated. The MUX SD signal is applied to
gate 9201 where it is gated with the BLKS EN 1 signal, before
being applied to the mask shift registers of Figure 93 as the
MUX COL 13 signal. This gating, before being applied to the
mask shift registers, insures that during six lines per inch
operation only the image of the desired line enters the mask.
That is, only the image of the desired line, with possibly
`` a little overflow from the lines immediately above and below
that line, enter the mask; however none of the desired line is
gated out. The data from gate 9201 is fed to the column 13
shift register 9313, and then serially in turn to the column 12,
1~1
~0~9147
1 column 11, etc. shift registers to the column 1 shift register
9301. The data enters each shift register 9301-9313 at terminal
A and exits to the next shift register stage from terminal B.
Each of the thirteen shift register columns are identical and
a typical column is illustrated in Figure 94.
Referring specifically to Figure 94, data entering the
shift register at cerminal A is gated at NAND gate 9404 by the
RDEN signal. Gates 9403,9404 and 9408 serve as a data stream
selective switch which enters the data from terminal A into the
shift register when the RDEN signal (read enable) is high. When
RDBN is low, and the recirculate signal is low, the output from
the shift register eolumn is fed back into the input via terminal
B. When the recireulate signal is high and the RDEN signal is
low, data is prevented from entering the register.
The shift register itself, designated 9405, is a
sixty-four bit MOS shift register, the 64 bits corresponding to
a full eolumn length. It is the purpose of the thirteen individual
shift register columns to juxtapose thirteen suceessive detected
slices of a character to provide a reassembled character which
can be recognized aecording to logic to be described below.
In this regard, eaeh column is sixty-four bits in length to
~ accommodate the sixty pho~co-diodes in the optical detecting array.
: ~lowever, the maximum height of any charaeter slice will be
significantly less than sixty elements high; in fact, for OCR-~
font the maximum eharacter slice hight is 18 elements of the
photo-diode array. For purposes of actual character detection,
therefore, a 24 bit DTL shift reglster, comprising 24 JK flip-flops,
., .
are associated with and included in each column. The selected
data stream, designated as si~nal COL (or COL) i5 applied both
to the 64-bit shift register 9405 and to the 24-bit DTL shift
register utilized for actual character sensing. Shift register
9405, therefore, is utilized to maintain proper column orientation
from co]umn to column; the 24-bits in the DTL shift register serve
to provide the signals utilized to detect the character.
The S/R clock signal, which is actually timing pulse
TPA, is utilized to clock the dual JK flip-flops in the 24-bit
DTL shift register. The signal is illustrated in timing diagram
Figure 49. The output signals in the individual 24 flip-flops
change states at the trailing edge of timing pulse TPA. The
clock signal for the 64-bit shift register 9405 is designated
MOS CLK and is derived from inverter 9205. The MOS CLK signal is
high from the beginning of timing pulse TPB to the beginning
of timing pulse TPD. It is inverted by invertor 9401 to clock
shift register 9405 once during each count interval of the
counter in Figure 90. After sixty-four MOS CLK pulses a data
bit is shifted through shift register 9405, inverted by inverter
9406 and applied to the A input terminal of the next ~hift
register column.
As illustrated, both the true and false output signals
from each of the 24-bit DTL shift register stages axe connected
to forty-eight respective matrix amplifiers to provide the
output signals 1-24 and 1-24. A typical matrix amplifier is
9 illustrated in detail in Figure 95.
183
..
Referring specifically to Figure 95, when the input
signal to the amplifier is at logic 1 level, the resistor diode
combination clamps the output signal to the matrlx to the level
of the collector supply phototransistor 9501. The base-emitter
drop in transistor 9501 cancels out the drop in the diode so
that during the binary 1 condition the output signal rises fully
to the collector supply level. During the zero condition the
matrix driver line drops to a level corresponding to the low
voltage provided by the JK flip-flop feeding the amplifier.
The output signals from the amplifiers are connected to various
character lines through resistor or resistor diode combinations
of the different mask figures. The true outputs are connected
; through resistors to respective character lines to denote those
areas where a character image is expected. The false output
signals are connected through resistors, or resistor diode
combinations to the respective character lines to denote those
areas where character image should not exist. This operation
is escribed more fully in the next section.
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I I I ( B . 2 ) CHAR ACTER MAS KS
Referring to Figure 97 of the accompanying drawings,
it is seen that the sixty-four character masks are actually
sixty-four individual 13 x 24 matrices. The thirteen columns
in each mask correspond to individual column shift registers
9301 through 9313. The twenty-four rows in each mask correspond
to the twenty four DTL bits (Figure 94) in each shift register
column. For ease in reference only one mask has been illustrated
in detail, namely the mask for the character "H". The plus signs
at matrix grid locations represent locations where the presence
of an image is expected Eor the character "H"; minus signs
represent those locations where no portions of the "H" should
appear. For example, a plus sign appears in column 2, row 5;
this corresponds to a true output signal for bit 5 of shift
register 9302. Likewise, a minus sign appears in column 5,
row 6; this corresponds to a false state for bit 6 in shift
register 9615. The outlines around the image "H" represent
the boundaries of that image of 3 elements in width. Thus,
imagining the boundary lines to represent a character superimposed
~ .
on the mask, the character can be shifted over one column in
either direction and still be recognized as an H. In effect then,
as the data is being shifted through the various columns, the
"H" can be xecognized during any one of three individual vertical
. ScaDs,
It is also noted that various grid locations in the
- matrix have multiple plus or minus signs; these indicate various
weightings attributed to the presence or absence of character
185
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10~9~L4~7
" portions at these locations. A single plus sign or a minus sign
has a weight of one, a double plus or minus sign has a weight of
two, a triple plus or minus sign has a weight of four, and a
quadruple plus or minus sign has a weight of eight. As mentioned
above the plus corresponds to the true state of the bit in the
appropriate shift register whereas the minus sign represents the
false state. The pluses and minuses are summed through various
resistors, with the resistors weighted as necessary, to provide
a cumulative signal level. An identical character match (i.e.
an "~I" position within the shi~t register stages as illustrated
in Figure 97) provides the signal of greatest magnitude for the
- mask bus corresponding to that character. As described in
subsequent sections, the mask plus having the highest amplitude
above a predetermined minimum amplitude has its character
recognized.
In addition to the plus and minus signs in individual
grid locations, certain minus signs in adjacent locations are
grouped, as illustrated by their common encirclement in the
"H" matrix of Figure 97. These negations are connected to the
mask bus for that character through diodes in order that the
absence of an image at those locations does not increase the
Z
degree of match (i.e. increase the amplitude of the bus signal)
but thè presence of an image decreases the degree of match
since the diode is rendered conductive in such case and lowers
the amplitude of the bus. qZhe reason for this grouping is
to permit di~erentiation between certain characters occupying
a small portion of the grid area. For example, the difference
186
Z,
`~tween a period and a space is quite small; the grouping
permits relatively sharp distinction between these two
characters. The sixty-four individual character mask buses
are applied to the best match detector as described in the next
section.
III(B.3) BEST MATCH DETECTOR
The best match detector circuitry is illustrated
in Figures 98 through 103. Each of the individual character
mask buses, derived as described in relation to Figure 97,
is applied to a respective line amplifier 9801 through 9864.
The amplifiers are grouped in four groups of sixteen amplifiers,
each group corresponding to a particullar bus, namely~ the SPL
(special) bus, which primarily contains special symbols, the
NUM (numeric) bus, which contains the ten numerals plus additional
special symbols: the ~l ~alpha 1) bus, which accommodates the :~
low end of the alphabet; and the ~2 (alpha 2~ bus, which
.
represents the high end of the alphabet. Amplifiers 9801
through 9816 are associated with the SPL bus; amplifiers 9817 `~ :
: through 1932 are associated with the NUM bus; amplifiers 9833
through 9848 are associated with the c~l bus; and amplifiers
;
~ 9849 through 9864 are associated with the ~ 2 bus. For example, :
: ~ the mask bus for the character "H" is connected to amplifier
- 9841 which is associated with the ~ l bus. The arrangement of
character lines and bus columns is represented in Table Rl
S wherein the buses correspond to the vertical columns and the
horizontal lines correspond to vertical rows of amplifiers in
Figure 98. Thus, the "H" ampIifier 9841 is in line 8 along
,:
; ' ' ":'', '
187
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~L~49~7
TABLE Rl
~b 7 - O O 1 1
~_ ' 1 1 1
~;~ b 3 1 b I L~E,~ S P~ NUM ot 1 2
O _--O--O O ' ' SP _=
O O O 1 1 1 A Q
O O 1 O 2 S P _ 2 B R
O O 1 1 3 T 3 C S
O 1 O O 4 $ 4 D T
O 1 O 1 5 % 5 E U
O 1 1 O 6 & 6 F V
O 1 1 1 7 7 G W
1 O O O 8 (. 8 H X
O O 1 9 ?_ 9 I Y __
1 1 1 1 1 2 _ _ K _
1 1 O t~ 14 _ _ M
1 1 1 l~ 15 / ? _ O
188
i
10~9~L~L7
with amplifiers 9809, 9825 and 9857. Amplifier 9841 is also
in the third column along with amplifiers 9833 through 9848.
Each of the SPL, NUM, c~1 and ~ 2 buses feed respective
amplifiers 9865, 9866, 9867 and 9868. All of amplifiers 9801
through 9868 take the configuration illustrated typically in
Figure 99. The base of transistor 9901 receives the mask bus
signals in the case of amplifiers 9801-9864 or the four master
bus signals in the case of amplifiers 9865-9868. The emitter
of transistor 9901 for each of amplifiers 9801-9864 are tied
to the respective buses with which those amplifiers are
associated. Thus, the emitter of transistor 9901 in amplifier
9841 is tied to the ~ 1 bus. On the other hand, the emitter of
transistor 9901 and each of amplifiers 9865-9868 is tied to a
~ bus. Considerlng first the sixty-four line amplifiers 9801-
9864, the one amplifier of the sixteen on each bus having the
highest or most positive potential at the base of transistor
9901 causes the emitter of that transistor to rise toward the
base potential. In so rising, the emitter causes the entire
bus and all other emitters connected to that bus to rise to that
potential. Since the base potential of all other transistors
9901 on that bus is lower than the base potential at the
amplifier causing the bus to rise, all fifteen other transistors
9901 on the bus are back-biased. It is only the single activated
line amplifier on any of the four buses, therefore, which
supplies current to the load resistor at the input of the
driver amplifier 9865-9868 for that bus~ Likewise, only the
single transistor 9901 for each bus conducts collector-emitter
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~rD49~L~7
current. This conduction through transistor 9901 cuts off the
otherwise conductive transistor 9902, thereby switching the
collector of that transistor from logic zero to logic one. The
output signal from the collector of transistor 9902 is utilized
in the circuits of Figures lOlA and lOlB as described subsequently.
With relation to the buses however it is seen that transistor
9901 for the one active amplifier on each bus provides a voltage
which approximates the voltage on the most positive character
mask bus. The amplifier of Figure 99 thus provides both the
voltage level of the most positive character line (at the emitter
of transistor 9901) and the identification of the character
line having the most positive voltage (at the collector of
transistor 9902).
Similarly the bus (SPL, NUM, ~ 1' ~2') carry g
highest level signal causes its associated amplifier (9865-9868)
to domlnate the ~bus and also provide an indication as to
which bus is carrying the highest signal level. Specifically,
if the highest recognition level is derived from the "H" mask,
; ~ the base of transistor 9901 in amplifier 9841 receives a higher
voltage than does the base of transistor 9901 in any of the
other amplifiers 9801 through 9864. This voltage is applied
to the ~ 1 bus whereupon it biases off amplifiers 9833 through
9840 and 9842 through 9848. It also activates amplifier 9867
which biases off amplifiers 9865, 9866 and 9868. The resulting
level on the bus corresponds to the voltage applied to
amplifier 9841, less certain circuit losses. The collector of
transistor 9902 and amplifier 9841 designates line 8 as the
190
., , :
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147
active line or row in table Rl; the collector of transistor 9902
and amplifier 9867 designates the ~ 1 bus as the active column
in table Rl.
The bus is applied to the amplifier illustrated in
Figure 100. The resulting amplified signal is designated MA~K
ANALOG and is applied to the circuit of Figure 103.
Referring to Figure 102 of the accompanying drawings,
the output signals from amplifiers 9865 through 9868 are applied
to a group of OR gates 10205 through 10207. Specifically, the
SPL bus is applied to gate 10205; the NUM bus is applied to gates
10205 and 10206; the ~ 2 bus is applied to gates 10206 and 10207;
and the ~ 1 bus is applied to gate 10207. These gates effectively
serve as a four line to three bit encoder, the three bits
representing the coded states of the four vertical columns in
table Rl. The three bits, designated D5, D6 and D7 thus
identify the bus which has been activated by a detected
character. In additlon signals D5 and D7 are utilized to
address the indlvldual multiplexer circuits 10101 through 10108
and 10116 through 10123 in Figures 101a and 101b. Thus, if the
special bus contalns the most positive character line, only the
outputs from the special bus are passed through the multiplexers
in Figures 101a and 101b. Whichever output bus signal is
selected at the multiplexers, its level is inverted by inverters
10109 through 10115 and 10124 through 10131 to provide the line 1
2~ through l]~e 15 signals. These signals are applied in combinations
to gates 10201 through 10204 serving as code converters to
encode the selected line signal into four low order bits
191
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~C~4~47
corresponding to the horizontal columns in table Rl. These bits
are designated Dl through D4 and combine with bits D5 through
D7 in Figure 113 to identi~y the character which has been
recognized.
The MASK ANALOG signal, derived from the ~ bus as
illustrated in Figure 100, is applied to amplifier 10301 in
Figure 103. Amplifier 10301 is a high speed comparator which
is utilized with flip-flops 10304, 10307, 10312 and 10316, and
four switches 10308, 10309, 10313 and 10317, to provide an
analog to digital conversion of the voltage level of the MASK
ANALOG signal. Specifically, the circuit provides a four bit
successive approximation to convert the analog signal into a
four bit code represented by the signals WAl through WA4. This
code is the binary representation of the analog signal level
from the mask analog amplifier. The four blt binary representa-
tion of the analog voltage, plus the seven bit character
identification code as generated in Figure 113, are fed to the
best match store circuits in Figures 109 through 118. Negative
~ NOR gate 10320 provides a WREN (write enable) signal whenever
; 20 any one of the flip-flops 10304, 10307, 10312, 10316 are set
to the one state at the termination of the analog to digital
conversion process, or any time the mask analog voltage rises
above zero. Since the mask analog voltage rises above zero only
when the character line with the highest signal voltage rises
above a predetermined threshold, the WREN signal occurs only
when a character line rises above that threshold, The analog
to digital conversion by successive appr~ imation is a
'~` '
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standardized technique and need not be described in detail
herein.
III(B.4) BEST MATCH STORE
The logic circuits constituting the best match store
circuitry are illustrated in Figures 109 through 118 of the
accompanying drawings. In Figure 113 there is illustrated a
sixteen by eight bit memory comprising memory units 11303 and
11304. These receive, for purposes of storage, the seven
signal lines Dl through D7 encoded in Figure 102. The address
lines for this memory unit are signals MAl through MA4 derived
from multiplexer 10902 in Figure 109. The signals MAl through
MA4, in the write mode, correspond to the WAl through WA4 signals
generated in Figure 103 as an approximation of the mask analog
.
signal level. If any of the WAl through WA4 signal~ is low,
the WREN ~write enable) signal at gate 11302 is high and, if
.
other conditions are met, proyides a write pulse for the memory
unit 11303, 11304. This pulse enters the data appearing on the
: seven lines Dl through D7 into the memory at the addresses
:~ ~ selected by signal lines MAl through MA4. At the same time, the
~; 20 lines WAl through WA4 are fed through multiplexer 10903 and are
: ~ ;decoded by the four to twelve line decoder 10903 to provide a .
~; signal on one of the twelve bin lines d~pending upon the states
of the four address lines WAl through WA4. The ~elected bin
line output signal~at decoder 10903 is then written into the
. 2~ ~ appropriate bit In regls~ter llOOl through 11003. The write
, ~ command for these registers is designated WRIT~ and is derived
from gate 11302 at the same time data i9 written into memory
. ~
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i 193
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~L~4~47
units 11303, 11304. At the trailing edge of the WRITE pulse the
BIN C~ signal (bin check) goes high at flip-flop 11609 to switch
multiplexer 10902 frorn the write to the read mode. In this mode
the level bins containing data are fed to the priority encoder
11101. This encoder encodes the highest order bin containing
data into a four bit read address signal RAl through RA4. This
address is fed through the four bit adder 10901 to the read side
of the multiplexer 10902. If the ADD BIT 1 and ADD BIT 2 signals
are both zero at this time, the address provided by adder 10901
through multiplexer 10902 corresponds to the address of the
character which is written into the highest location in the memory.
The data which has been stored in the highest location in the
memory is immediately transferred into register 11401 on leading
edge of the next TPB pulse.
1~5 ~ The ADD BIT 1 signal and ADD BIT 2 signal are generated
in the circuitry of Figure 118. This generator is set to zero
,
~ ~ by timing pulse TPF and is advanced sequentially upon the trailing
!
edges of TPB, TPC, TPD and TPE. Therefore, initially both ADD
BIT 1 and ADD BIT 2 are zero and so remain until the trailing
edge of pulse TPB. Immediately after the trailing edge of TPB
the ADD BIT 1 signal goes high and effects the addition of one
bi;t at adder 10901. The address bits RA1 through RA4 are negative
so that the addition of one bit t~o the minus number effectively
decreases the address by one. Addèr lO901 thus generates a new
25~ ~ memory address for the bin immediately below the highest level
bin in which data was written. This produces an output signal
.: ~
; ~ from decoder 10903 on the bin line which is one below the highest
194
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, . .
~6)4~47
level stored. This is compared, in the circuitry of Figure 112,
against the output signals from register 11001, 11002, 11003 to
determine whether or not data has been stored in that next lower
order bin. At the same time the memory data bit:s 1 through 7
at memory unit 11303, 11304 are compared with the bits stored in
register 11401 at comparator 11501, 11502. If the data stored in
memory unit 11303, 11304 immediately below the highest order bit
is the same as in the higher order bit, the COMP OUTPUT signal
frorn comparator 11502 goes high. This COMP signal is inverted
by invertor 11606 to enable gate 11602. If the low bin were
occupied and the COMPARE signal were low (in other words the
date in the bin immediately below the highest level stored were
not compared), gate 11602 is actuated which setc; the recognition
inhibit flip-flop 11603, 11604 at timing pulse ~lPCO On the
trailing edge of TPC the add bit counter 11808, 11809 advances
to the count of two. This subtracts two from the address of the
highest stored location and again, at the TPD pulse, the contents
of memory unit 11303, 11304 are compared against the stored
outputs to determine whether or not the recognit:ion inhibit
flip-flop should be set. On the trailing edge of TPD the add
bit counter advances a third step, subtractlng t:hree
from the address of the highest stored at TPE. Again a check
is made to determine whether this bin has data in it, and if
the data agrees with the data in the top most ctored bin. At
the end of TPE, counter 11808, 11809 advances back to zero count.
If during any of the previous steps the recognition
inhibit flip-flop 11603, 1160~ had been set, gate 11711 would be
195
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~ ` . ~ \
~04~ 7
inhibited to prevent generation of a charac~er recognition signal
(CHAR REC) at flip-flop 11712, 11713. While the bin checks are
in progress, the read address signals (RAl through RA4) are fed
to the circuit of Figure 117 where it is determined whether or
not the signal with the highest stored level is of sufficient
level to justify generation of a CHAR REC (character recognized)
signal. If RA4, RA3 and either RA2 or RAl are enabled, gate
11709 is enabled to cause gate 11710 to apply a high signal to
gate 11711. If the recognition inhibit flip-flop is not set
; 10 (REC INH is high) and the RDEN (read enable) signal is high gate
11711 goes low at the next TPF pulse to set the character
recognized flip-flop 11712, 11713. If the recognition inhibit
flip-flop 11603, 11604 has not been set (RE~ INH is high), and
if the read enable signal (RDEN) is high at TPF time,gate 11711
15 goes low to set the character recognitlon flip-flop 11712, 11713.
Similarly if signal RA4 is low and either R~2 or RA3 is low
.;
(a read address correspondlng to 10, 11 or 12) and the window
signal is high,gates 11708, 11710, 11711 are actuated to set the
recognition flip-flop again.
When the CHAR REC signal is high gate 11714 is enabled.
At TPD gate 11714 generates the G R~C signal which is connected
~ to flip-flop 11719, 11720. The resulting MPRW signal from the
; flip-flop is the MACHINE PRI~T WRITE signal utilized in Figure
121. The machine print write flip-flop 11719, lL720 is also
25 triggered by a SPACE signal. The TPD pulse following initiation
of a SPACE signal enables gate 11718 providing a low output signal
from that gate. This signal, or a low ERROR signal can also set
';
196
1~49~
the MPRW flip-flop~ Thus the MPRW flip-flop may be set by a
character recognition, a space character detection, or a read
error condition. The CHAR REC signal goes high at the leading
edge of TPF; the G REC (gated recognition) signal goes low at
TPD. The reason for the delay is to permit the window delay
flLp-flop 11715 to remain high long enough to set the character
recognized flip-flop 11712, 11713 before the window delay
flip-flop has been reset. The DELRST (delayed reset) signal,
__
the G ~EC (gated recognized) signal and the ERROR (read error)
signal, all active low signals, are fed to gate 11716. Any
of these signals going low resets the window delay flip-flop
11715. This flip-flop remains reset, with the WIND DEI.AY signal
low, until the beginning of the next window time when the window
signal is received to clock flip-flop 11705. The purpose of the
window delay is to inhibit generation of additional recognitions
until the following window time, so that multiple recognitions
cannot occur.
. . ,
The MCD (maqk centered delay) signal is utilized during
step RPS10 of the read program. When step RPS10 is not active,
,
signal RP510 is h1gh producing a low level at one input of gate
~ 11802. When the DELRST s~ignal goe~ high the MCD signal goes high.
`'1 During step RPS9 however signal RPS10 is low and gate 11802 does
` ¦ ~ not go low until the beginning of the fir~t window time when the
signa1 WINDOW goes low. This causes the MCD signal to remain
, 25 low keeping the RESET 4 signal~low until the beginning of the
, ; first window time during RPS9.
,
. :
,
~ 197
III(B.5) LOW DENSITY SCALER
The low density scaler circuits are illustrated in
Figures 92 and 96. This unit ser~es three major functions:
(1) generation of various shift clocks, (2) generation of the
mask centered signals; and (3) gating of MUXSD (serial data)
signals.
A two-input AND gate 9201 gates the MUXSD signal from
shift register 8983 with the BLKS EN 1 signal to provide the
multiplexed data (MUX COL 13) which is sent to shift register
9313. The BL~S EN 1 pulse reduces to thirty-eight columns in
width for six lines per inch operation during load format time,
and widens to fifty colum~ at six lines per inch operation during
read time.
; As mentioned in relation to the quantizer multiplexerdescription, the MUX CLK signal comprises the timing pulse train
TPA with the first pulse after MUX63 time deleted. This signal
is generated at gate 9202 with the aid of flip-flop 9203. MUX63
' i9 fed to the D lnput of flip-flop 9203; timing pulse TPC is
: fed as a clock lnput; thus, at TPC during the MUX63 count interval,
the high MUX63 state is transferred as a low to the Q output of
flip-flop 9203, thereby inhibiting gate 9202. The flip-flop
9203 is not reset until the next TPB pulse; thus the ~PA
'~ immediately following MUX63 is disabled during the one count
interval after MUX63. `.
Fllp-flop 9204 is utilized in the generation of the
MOS CLK signal. The D input of flip-flop 9204 is continuously
held high; thus at TPB time the positive-going clock for
: .
198
.
flip-flop 9204 transfers the high D input to a low Q output which
causes inverter 9205 to go high. This high remains until flip-
flop 9203 is reset by timing pulse TPD so that the MOS CLK signal,
which rises at the leading edge of TPB, falls at the leading edge
of TPD.
The mask centered determination is performed by registers
9601-9603 in conjunction with AND gates 9604-9607 and 9609. Enter
pulses for registers 9601-9603 are produced for each shift of the
image through the thirteen shift register columns (i.e. each
vertical shift of the image through the mask) by the DEW pulses
derived at gate 9209. The BLKS EN 2 pulse, which is approximately
twenty four shift elements in width for six lines per inch ~
full height at three lines per inch operation, is applied to gate
9209. The output for this gate goes low for each TPP pulse during
the blacks enable 2 interval. The resulting DEW signal therefore
enters into registers 9601-9603, an indication as to whether
`-~ a black or logic 1 is entering each of shift registers 9301-9312
at that time. If a black is entering the particular shift
~ :
register at that time, the COL signal for that register is low.
This low is entered into the appropriate bit of registers 9601
9603 where it remains until the cleax W time (signa1 CLR W),
which occurs after the foIlowing MUX63 interval. Therefore,
any black or logic one entering a shift regi~ter column causes
an indication at registers 9601-9603 no~matter what position
that black or logic one occupies in the mask, as long as that
black or logic one coincides with a blacks enable 2 time frame.
:~,
~ The thirteenth shift register coLumn 9313 is handled 5imilarly
.
:
'
.
,
. ~ ' " ' '' ' ' .,
~L04~
except that it is applied to flip-flop 9611 via AND gate 9610
which is al50 gated by the DEW pulse. If a black appears in
column 13 during any TPF pulse, AND gate 9610 provides a logic
one which sets flip-flop 9611. This flip-flop remains set until
the CLR W pulse resets the flip-flop. It is to be noted that
a low applied to the input of a stage in register 9601-9603
is reflected as a high at the corresponding output terminal
for that stageO
A mask centered condition, represented by the MASK CENT
signal, occurs if there is data or a blacks indication in any of
columns 2 through 6 (i.e. shift registers 9302-9306) but no data
in shift register column 9301. If there is no data in column 1,
the Wl signal, derived from register 9601 and inverter 9608, is
high. If there is data in column 2 the W2 signal derived from
register 9601 is high. If there is data in columns 3 through 6,
the W3456 signal derived from gate 9605 is also high. These
three signals are all applied to AND gate 9206, and when all are
high they enable gate 9207. If there is data in the mask, the
mask full signal is high so that at MUX63 time ~ate 9207 is
actuated to provide the MASK CE~T signal.
Gates 9604, 9606 and 9607 are utllized~to determine
If all thirteen channels ever have data entered therein
simultaneously. If this condition occurs a straight line has
,~ been detected causing NAND gate 9609 to go low resulting in a
,, _ .
low SL signal. This signal indicates that a line wider than
any character width has been detectcd and therefore, insofar
as resynchronization of the column counter window generator
200
~. . .
.
' .
1~4~47
is concerned, a MASK CENT signal cannot be expected to occur
within the normal one character spacing.
The CLR W signal (clear window) which occurs slightly
after the MUX63 interval, is generated at gate 9617. The TPD
S pulse occurring during MUX63 interval causes gate 9612 to provide
a low output signal and thereby set flip-flop 9614. At N/2 time,
which occurs two counts after the MUX63 interval (reference timing
diagram Figure 49), one input to NAND gate 9617 is high. At the
next TPB pulse gate 9617 is actuated to provide the binary 0 CLR W
pulse. In the interim, the MUX63 signal has gone low causing
inverter 9613 to go high. Therefore at the next TPD pulse during
the N/2 time after MUX63 occur:, flip-flop 9614 is reset.
` Consequently, only one CLR W pulse is generated`during the scan
cycle, and that pulse is coincident with the TPB timing pulse
occurring approximately two counts after MUX63.
:
.~ :
: ~
., :
. ' , .
201
.
1~4g~9L7
III(B.6) COLUMN COUNTER AND WINDOW GENERATOR
The logic circuitry for the column counter and window
generator i5 illustrated in Figures 104 through 108 of the
accompanying drawings. The column counter may be considered as
a fly wheel which is synchronized to the character spacing for
the particular format being read. The purposes of such fly wheel
are: (1) to identify those times when a second character should
be present; (2) to identify the times when a space character
should be generated; and (3) if a character is not recognized,
; 10 to determine the time at which a "character non-recognized"
signal should be generated. The basic counting circuitry is
composed of two divide-by-16 counters 10401, 10402. These are
connected together in a normally divide-by-256 configuration;
however, the counter is recycled for different operating modes
lS as follows: at count 17 during OCR-A 8 pitch operation; at
` count 28 during OCR-A 10 pitch operation; at count 23 during
front 7B 6 pitch operation; at count 20 during font 7B 7
pitch operation; at count 33 during hand written 4.3 pitch
operation; and at count 28 during hand written 5 pitch operation.
Since recycling occurs at the end of one of these counts, the
` : ~
:
counter division ratio variesF For example, during OCR-A 10
pitch operation, the counter becomes a divide by 29 counter.
'~ That is, a cou~nt of 28 is fed into data selector multiplexer
10412. When the count of 28 is reached at counter 10401, 10402,
the RECYCLE signal goes low at the load inputs of the counters.
At the following clock~time (i.e. the trailing edge of MUX63 G
when the clock inputs to the counters go high), the information
202
9~9~7
on the parallel data inputs is transferred into the counters.
Since the parallel data inputs are all grounded, the counters
recycle to a count of 0.
The six output bits Ao through Fo of counters 10401,
10402, are decoded in the circuitry of Figure 105 to provide the
various count signals utilized at multiplexer 10412 to provide
the RECYCLE signal under the specified operating formats. For
example, decoding of the 28 signal applied to multi-
plexer 10412 i5 effected at NAND gate 10510 which receives the
C0, Do and Eo bits from counters 10401, 10402. These bits all
become high at the start of count 28, at which time the 28
signal goes low.
The two eight-input data selector multiplexers 10405,
; 10406 are employed to select the proper counts at whieh to begin
and terminate the window for the various fonts and font spaclngs.
For example, for OCR-A operation, the window is started at the
count of 10 and then again at the count of 24. The signal
10 + 24 goes low at counts 10 and 24 and appears at this low
level during those counts of OCR-A operation is in effect.
If OCR-A 10 pitch operation is in effect, the MUX63 G signal,
which is actualIy timing pulse TPF during the MUX63 interval,
then drives gate 10407 low to provide a high WINDOW signal at
~; the output of flip-flop 10409, 10410. This WINDOW signal
~ thus goes high during counts 10 and 20 at counters 10401, 10402.
j ~25 At count 3 or 18 multiplexer 10406 provides a low signal to
prlme gate 10408. This gate is enabled by signal MUX63 G to
reset flip-flop 10409, 10410 at counts 3 and I8. From the
,~
r ~ 203
' , :
''
~9~ 7
foregoing it is seen that the WINDOW signal, for OCR~A 10 pitch
operation, goes high at the count of 10 and low at the count of
18, and then goe~ high again at count 24, remaining high as the
counter recycles at count 28, until ~he count of 3 i~ reached
at which time the WINDOW signal goes low. Gates 10407 and 10408
are clocked by the inverted MUX63 G pulse which defines the no~mal
times for turning the WINDOW signal on and off; however, an
additional signal may be utilized to actuate the WINDOW signal.
This signal is called MCRG which is derived at gate 10806 and
describ~d in detail subsequently. The RDEN signal is utilized
to inhibit generation of the WINDOW signal during the time RDEN
is low (i.e. no read enable).
Data selector 10411 is utilized to generate the M WIND
(mid window) signal. The mid window condition occurs at various
counts of counters 10401, 10402 during different operating modes,
as follows: At counts 14 or 28 during OCR-A 10 pitch operation;
at count 17 during OCR-A 8 pitch operation; at count 20 during
7B font 7 pitch operation; during count 23 in 7B font 6 pitch
operation; at count 28 during hand written mode~5 pitch operation;
; 20 and at count 33 during hand written mode 4.3 pitch operation.
The M WIND signal is utilized in conjunction with the blacks
. . .
counter 10702 to determine whether or not a SPACE CHARACTER
signal (SPACE) should be generated.
The circuity for determining the proper pitch is
illustrated in Figure 105. Primary pitch contr~ effected
by the font switches at the control panel con~ector board. When
~ont A is selected, the FONT A SW si~nal iB low and actuates
1; ' ' ' '
l 204
.'.~ , .
.~ _, .5_
'
~9~ 7
gate 10523 to provide a high 10 pitch signal. Since the font
switch is a rotary switch, only one font at a time may be
selected. When font B is selected, gate 10520 is actuated to
provide a high 7 pitch signal. When the font selection switch
is moved to the mixed position, the MIXED signal goes low and
drives inverter 10525 high. If the load format mode (LDFT) is
not in effect, gate 10524 provides a low DECEN ~decode enable)
signal which is fed as an enable input to three-bit to eight-line
decoder 10517. This decoder converts signals HCRll, PITCH 1 and
PITCH 2 to an indication of the proper font as follows: If these
signals represent octal 0 or octal 1, handwritten 10 pitch is selec-
ted. For octal 2, 7 pitch font B is selected; for octal 3, 5 pitch
is selected, for octal 4 or octal 5 OCR-A 8 pitch is selected,
; for octal 7 handwritten 4.3 pitch is selected. During load
format, the decoder is disabled and since the LDFT (load format)
signal is low, gate 10523 is actuated to force 10 pitch
operation. Thus, in load format mode, the system automatically
switches to OCR-A 10 pitch operation.
The pitch selected as a result of the font switch
position, the load format condition, and/or the HCRll, PITCH 1,2
:
conditions from main memory, and re-encoded into a three bit
; slgnal is designated CTR BIT 1, CRT BIT 2, and CTR BIT 3 (counter
' bits 1-3). CTR BIT 1, the output of gate 10512, is high unless
hand written 4.3 pitch or hand written 5 pitch are selected.
CTR BIT 2, the output of gate 10513, is high if OCR 10 pitch
or OCR 8 pitch are selected. C~R BIT 3, ~he output of gate
10516, is high if OCR-A 8 pitch, 7B font 6 pitch, or handwritten
205
'
~49~7
4.3 pitch are selected. These counter bit signals are utilized
as the address input signals for the data multiplexers 10405,
10406, 10411, 10412 to provide proper window timing and spacing.
Figures 106 through 108 illustrate the basic circuitry
utilized to maintain the window counter synchronized with the
data and to determine if a space, error, or "delete line" is
detected. Serial data (MUXSD) from the quantizer multiplexer
enters the blacks counter 10702 as serial data when the system
is in OCR-A operation. The SHIFT CLOCK pulses clock the data
into counter 10702 so that output data from the quantizer
multiplexer is fed to the counter as it is shifted into column
13 shift register 9313. For each black (logic 1) shifted into
the 9313 shift register, one count is added to counter 10702.
During OCR-A operation, CTR BIT 2 is high so that AND gate 10703
is primed. When outputs C and D of counter 10702 are both high
ti.e. a blacks count of 12 has been reached), gate 10703 is
enabled and applies a logic 1 signal to the J input of flip-flop
10707 via OR gate 10706. At the end of the next TPA pulse this
logic 1 is transferred to the output of flip-flop 10707 to
provide the MASK FULL signal. Mask full goes high, therefore,
on the first shift pulse,(TPA) after twelve blacks have been
'~ ~ counted at counter 10702. If either hand written or 7B font
is selected, CTR BIT 2 goes low, disabllng gate 10703. Counter
10702 then must count to 15, at which time the carry output
of the counter clocks flip-flop 10704 to drive its output
high and prime gate 10705. Counter 10702 again counts up to
fifteen and enables gate 10705 to apply loyic 1 to the J input
206
~'
`~\ ~
147
of flip-flop 10707. Thus, for handwritten or 7B font, 31 blacks
must be counted before a MASK FULL signal is generated. The
blacks counter 10702 and MASK FULL detector 10703-10707 are
cleared each time a character is recognized, a space is detected,
or an error signal is generated as discussed subsequently in
relation to the generation of the RESET 2 signal.
Assume that no new blacks have entered the blacks
counter 10702 since the last character recognized signal was
generated. In such case the MASK EMPTY signal from flip-flop 107
is high and is applied to gate 10710. If the system is in the
read mode rather than in load format, the LDFT signal also
primes gate 10710. At mid window time, the M WIND signal is
high so that when MUX63 and TPE actuate gate 10709 during
mid wlndow time, NAND gate 10710 is enabled and provides a low
signal at flip-flop 10712, 10713. This sets the flip-flop and
generates a high SPACE signal. ~If, however, at least 12 blacks
have been counted by blacks counter 10702 before mid window
time is reached, the mask full fllp-flop 10707 is set, causing
gate 10710 to be inhibited and preventing generation of the
i
SPACE signal.
If the aseemblage of detected blacks entering the
array is unrecognizable, the error detection circuitry in
:
Figure 106 provides an error indicatlon. The end of window
detector includes two-bit counter;10606, 10607 which changes
l 25 state on positive-going edges of clock input TPA. When the
window signal i~s high, the Q~output of flip-flop 10606 is low
and the Q output of flip-flop 10607 is high. Immediately after
~. , : ,
,` : ~
. !. 207
~:
,.. . .
9~7
the window signal goes low, the following TPA pulse causes the
Q output of flip-flop 10606 to go low, enabling the negative
AND gate 10605 and providing a high input signal to gate-1~604.
Since the ~SK FULL signal has already been genera~ed, another
input to gate 10604 is high. Assume that the WINDOW DELAY signal,
the READ ERROR INHIBIT signal (REI), and the ERROR RESET INHIBIT
(ERI ) signal are high. Therefore at TPD time gate 10604 is
enabled, setting the read error flip-flop 10602, 10603 causing the
:
ERROR signai to go low to provide an error indicatlon. ~he
second shift pulse (TPA) after the window signal goes low
causes the Q output of flip-flop 10607 to go high, disabling
gate 10605, removing the set signal to the read error flip-
flop 10602, 10603. The ERROR signal i5 fed through gate
10601 as a high RERF (read error flip-flop) signal, which
is sent to the main memory as a reader reset flag.
The read error flip-flop 10602, 10603 and the space ~-
flip-flop 10712, 10713 are both reset by the RESET 4 signal.
RESEr 4 is generated by the circuit in Figure 108 and is provided
.~ .. . , , :
hy either the DELRST signal going Iow or the ACK (acknowledge)
~20 going high. The ACK signal results from completion of a write
cycle at the maln memory. The DELRST signal is discussed
subsequentlyO When the main memory has acted upon the ERROR
or SPACE signals, a memory cycle complete indication is
provided and inverted to the ACK signal in the circuit of
Figure 120. The ACK signal is then passed by gate 10816 as ,
a low signal to provide the RESET 4 si~nal which resets the
.
space and read error flip-flops.
208
.
~ , .s, 2~ ~
., .~ . , , , ~ . . .
. .
The delayed reset generator includes inverter 10825,
flip-flop 10823, and NAND gate 10824. A low RDEN signal is
inverted by inverter 10825 and fed to the data input terminal of
flip-flop 10823. This flip-flop is clocked by the MUX63 G signal
(TPF during MUX63). The low RDEN signal is also applied to NAND
gate 10824. When the read enable condition is not active, signal
RDEN is high and the Q output of flip-flop 10823 is high. Gate
10824, having both inputs high, provides a low DELRST signal.
During a read enable condition, the RDEN signal is low causing
gate 10824 to provide a high DELRST signal. Sometime after the
read enable condition has been activated, flip-flop 10823 is
clocked by the MUX63 G signal to drive the Q output signal from
that flip-flop low to further disable gate 10824. When the
read enable condition is deactivated, signal RDEN goes high but
; 15 flip-flop 10823 maintains gate 10824 in its disabled condition
'~ so that the DELRST signal remains high. This condition subsists
until flip-flop 10823~is next clocked by the MUX63 G signal at
which time gate 10824 is enabled to provide a low DELRST signal.
Thus, DELRST goes high in time coincidence with activation of
? ~ : :
the read enable condition but stays high for a time duration
after the read enable condition has been deactivated. This time
duration is approximately 120 microseconds; that is, the time
duration lS sufficient to permlt completion of any signalling
between the recognltion circults and the master memory after
,...................................... ~
2~ 25~ the read enablé condition has deactivated.
. . g
!'~ : The RESET 1 signal is generated by gate 10814 and
~ - inverter 10815. The input signals to negative OR gate 10814
~ :
~ 209
~, .
,
~4~
.
are the DELRST signal, the GMCR signal, and the CHAR REC sîgnal.
The GMCR (gated mask center reset) signal is discussed
subsequently. When any of these signals goes low, the output
signals fro~ gate 10814 goes high to provide a low RESET 1 signal
at the output of inverter 10815. This signal is utilized to
reset the end of window detector in Figure 106.
The RESET 2 signal is generated by gate 10809 and
inverter 10811. RESET 2 goes low if either a SPACE, ERROR,
CHARACTER RECOGNIZE, or DELAYED RESET signal is received.
RESET 2 is utilized to reset the blacks counters 10702 and
the MASK FULL flip-flop 10707.
The RESET 3 condition is similar to the RESET 1
condition in that a mask center reset, a character recognized
or delayed reset condition produce a high RESET 3 signal as
long as signal ERI remains high. The ERI signal is fed to gate
10813 and permits that gate to provide the RESET 3 signal when
; any of the aforementioned conditions are met. RESET 3 is
utilized to reset the window counters 10401, 10402.
The gated mask centered reset condition occurs only
for the first character after a space or after the read enable
flip flop is set; that is, the first character is being read
in a line or a field. The GMCR signal is generated by circuitry
in Figure 8. As previously stated, the SPACE slgnaI lS inhibited
in load format mode by the LDST signal at gate 10710. This is
necessary beaause the main memory, in load format mode, stores
only the locations of active characters and not of space
characters. In order to accommodate both the regular read mode
210
.. . . . . .
.
.',.'. ," . ,, ,. '.. '... .' ', .'' ; . , '
~9~4~
and load format mode, an auxiliary pseudo (P SPACE) signal is
generated at gate 10708. The signal goes low at mid window time
whenever a MASK EMPTY signal is de-tected, whether or not the
system is in load format mode. The P SPACE signal is fed to gate
10803 which is cross coupled to gate 10802 to define the read
error inhibit flip-flop. The other input to the set side of this
flip-flop is DELRST (delayed reset) so that after DELRST or
P SPACE go high, the flip-flop output remains high and generates
a low REI (read error inhibit) signal at inverter 10810. The
REI signal, as previously mentioned, is fed to gate 10604 in
the read error detector. Thus, when the read error inhibit
flip-flop 10802, 10803 is set, the READ ERROR signals are
; inhibited. The read error inhibit flip-flop remains set until
the CHAR REC signal goes low or an REIRST (read error inhibit
reset) signal goes high and is gated by TPE. When the read error
inhibit flip-flop 10802, 10803 is set, its high output is fed
to gate 10805 as a high level. If a high MCD signal is received
at gate 10804, the output of that gate goes high during each
TPD interval thereafter, priming gate 10805 at each TPD time.
When a MASK CENT signal is received a~ TPD thereafter, the output
of gate 10805 goes low. This low signal is the GMCR signal
(gated mask centered reset). This is one of the~ RESET signals
used to reset window counter 10401, 10402. The window counter
being reset at mask center time allows for additional time
to obtain a character recognition before an ERROR signal is
produced. A mask centered condition occurring at read error
inhibit time causes gate 10805 to also actuate gate 10806
211
~4~7
when RPS9 is high (in other words during step RPS6). When RPS9
is high gate 10806 is enable~ producing a low MCRG signal. This
gate is fed to the window generator circuit of Figure 104 and
serves to turn the window on as soon as a mask centered condition
occurs during RPS6, after either spaces have been received or
the read enable has just been set. Thus, not only is the window
counter 10401 reset to zero by MCRG, but the window is turned on
at MCRG time (at mask center time in this case during read error
inhibit).
During RPS9, due to the fact that the read enable is
turned on just as the new character is entering the mask matrix,
the previous character is in the mask matrix. Thus if read
enable is turned on slightly early, a premature mask centered
condition could be produced. For this reason the MASK CENT signal
does not turn the window on during RPS9. During RPS9 gate 10413
is raised to a high level by the MWIND (mid window) signal to
provide a GMWIND (gated mid window) signal. This signal is
fed to gate 10818 and, if mid window is reached during MUX63 G
time, gate 10818 resets flip-flop 10820. This flip-flop had
been turned on by the WI~DOW signal going low. When the WI~DOW
signal goes high the flip-flop remains on until the GMWIND
, signal is received. The BLKS EN 2 signal is only high from the
i time the WINDOW signal is high during RPS9 until the mid window
` condition is reached or a mask center is reached. The blacks
counter 10702 is only enabled these two times. The circuit is
required during operation at six lines per inch to reduce the
possibility that the trailing edge of letters in the line above
212
~, ''
or line below will produce erroneous mask full condition if a space
were actually being scanned in a desired line. Further, if
these blacks from adjacent lines are toward the right hand edges
of their respective characters, they could delay the window
generated by the MASK CENTERED signal such -that during successive
RPS9 rescans, when the left hand edge of the character following
the space is coming into the array, by the time the end of
window is reached this again could produce erroneous mask full
conditions. For this reason, the absence of a MASK FULL signal
at gate 9207 inhibits the MASK CENT signal and thus random
blacks or blacks from the right hand portions of characters
above or below the line during six lines per inch operation,
cannot produce an erroneous mask centered condition. In other
words, as has been previously stated, the mask center condition
can cause the reset of the window counter immediately after
a space or immediately after~the read enable flip-flop has been
set.
:, ~
213
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~L0~91~7
DATA CONTROL
The data control circuits are illustrated in Figures
119 through 124 of the accompanying drawings. The main functions
of the data control circuits are: (1) generation of the end of
field character, (2) generation of the space character; (3)~e~
errors, and (4) correlating these functions with the output signals
from the best match store circuits. The data control circuits
also generate the vertical window utilized in six lines per
inch operation.
The four-line to two-line multiplexers 11902, 11903,
11904, are illustrated in Figure 119. If the address inputs to
these multiplexers are 00, the machine printing bits MPBl-MPB6
are connected through to the RDCl-RDC6 data outputs. The signals
that modify the addresses at the multiplexers are the SPACE
;~ 15 signal, the HWMASK signal, the E~RO~ signal, and the EOF (end of
; field) signal. When the system is in the hand written mode or~ in the 7B font mode the MASK signaI is high causlng a high
; ~ lnput at gate 11915. If a character is recognized and a spaceis not generated, the other lnput to gate 11915 is also high and
this causes the gate output to go high. If an error is not
; present one input of gate 11911 lS high, causing the OUTPTJT signal
- ~ ~; from that gate to go low and therefore drive gate 11912 high.
` Since the ERROR signal is high and the EOF signal is also high
(no end of field), gate 11913 remains low. Thus the address
:
~ 25 code to the multiplexers is 01, causing hand written bits (not
.. . .
'~ used) -to be transferred through the multiplexers to the RDCl
.. :
through RDC4 data outputs. Hand written data bits S and 6 are
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~6~4~47
connected to positive voltage to produce a high on RDC5 and RDC6.
If RDC6 is high, gate 11914 provides a low for RDC7. If an error
is detected, gate 11911 is disabled. In this case the level from
gate 11912 drops to zero; however the ERROR signal fed to gate
11913 causes the output of that gate to go high. Therefore the
address code is 10, in which case RDCl through RDC5 are high,
RDC6 is low, and RDC7 is high. This is the character code for
an underline, which is utilized in the system to denote an error
character. When a space is detected during hand written operation,
- 10 the positive-going space signal inhibits gate 11915. This
disconnects the multiplexer data lines from the hand written
decoder and reconnects the data lines to the machine print bits
MPBl-MPB6. This is done because the space code is generated in
the best match store circuits fed by MPBl through MPB6.
An end of field code produces a low EOF signal at inputs
to gates 11912, 11913, causing the outputs of both gates to go
high. The address input to the multlplexers is then 11. Under
this condition RDCl and RDC4 are connected to B+, RDC2, RDC3,
RDC5, and RDC6 are connected to ground. Gate 11912 produces a
low at RDC7 which generates the TAB signal,(1.e. the HORI~OMTAL
TAB signal which is utilized as a field separator~. RDCl through
RDC6 are fed to the main memory.
Gate 11916 is utilized to decode the ovèr-strike
character when MPBl and MPB2 are high, and MPB3 through MPB6
,
.~ 25 are low. The resulting low provided~by gate 11916 is inverted
by inverter 11917 to high level and sent as~an over-strike
flag to main memory.
215
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~4~47
In Figure 124 data bits RDCl through RDC7 are fed to
exclusive OR gates 12401-12407. These gates provide RDC8 which
is the odd parity bit for data bits RDCl through RDC7. RDC8 is
also fed to the main memory.
The EOF signal is generated in circuit of Figure 121.
During read enable, the RDEN signal is low. If the system is
in read program step RPS6 and in mixed font operation, gate 12101
is low and combines with the low RDEN signal at gate 12103 to
drive that gate high. This provides a high at the data input of
flip-flop 12105. Normally the MCYC and MPRW signals are high
and prime gate 12102 so that the normal condition is to allow
the TPE pulses to be passed to clock flip-flops 12105 and 12106.
Thus, during the read mode, the Q outputs of flip-flops 12105
and 12106 are normally high. The data input to flip~flop 12107
is held high while the clock is held low. When RDEN goes high
(i.e. no read enable) gate 12103 goes low. If this happens
during MCYC cycle or during an MPRW period, gate 12102 goes
low. As soon as these signals go high again the following TPE
pulse is fed through gate 12102 as a high signal which transfers
the low data input at flip-flop 12105 to the Q output of that
flip-flop, causing the Q output to go high. This causes the Q
output of flip-flop 12107 to go low and provide a high OCRW write
command from negative NOR gate 12107. At the same time the low
EOF signal (end of field) is provided. When the main memory
has acted upon the OCRW write command, the RE~ET ~ signal goes
high, resetting flip-flop 12107. In the meantime the following
TPE pulse transfers the low data input at flip-flop 12106 to
,
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91~7
` the Q output of that flip-flop, disabling the data input to
flip-flop 12107. Thus the outputs of flip-flops 12105, 12106
are so arranged that flip-flop 12107 is set only at the negative
goi.ng transition or shortly thereafter of read enable. Thç normal
machine print write command MPRW from the best match store is
fed to gate 12108 where it is combined in an OR function with
the EOF signal to produce the OCRW commands.
The data control circuits also contain three vertical
window generators (Figs. 122, 123) required for six line per inch
operation. These vertical windows comprise the following signals:
BLKS EN 1 (blacks enable 1), which is required for enabling the
mask and the line position analysis circuitry; ~LKS EN 2 (blacks
enable 2), which is utilized for enabling the blacks counter
10702; and WRINH (write inhibit) which inhibits the write enable
command except in those vertical periods when a valid character
recognition should occur. The positions o these windows in
: time vary with respect to the MUX63 interval, depending upon thedetermination by the line position an~lysis circuits as to where
the centerpoint of the next line should be. The main control
signals for the starting and stopping of the various windows
are provided by the output counts of the multiplex count of
Figure 90. These are MUXA, MUXB, MUXC, MUXD, MUXE, MUXF. Adders
12201, 12205 are four bit adders which are combined as a six
bit adder and serve to add the count from the multiplex counter
; 25 (Fig. 90) to the derived count from~the line position analysis
circuits (bits FMCK4, 8, 16, ~'~). The two least significant
FMCK bits are not transmitted from the line position analysis
';
. 217
~ 7
circuit. Bit FMCK4 is fed to inverter 12202, FMCK8 is fed to
inverter 12203 and FMCK16 is fed to inverter 12204~ In the line-
centered condition, FMCK32 is high, FMCK4, 8 and 16 are low.
By inverting FMCK4, 8, and 16, an effective count of 31 is
added to the outpu-t of line position analysis circuit. With
the carry input to adder 12201 held high, an additional one bit
is added. This therefore adds a count of 32 to the output of
the line position analysis circuit, which produces a total
addition of 64. In other words, the ~ A through ~F outputs
from adders 12201 and 12205 rise in coincidence with the respective
MUXA through MUXF inputs. However, if the line position is found
to be four counts high, the signal sent from the line position
analysis circuits is the count 28. That is, FMCK32 is low where-
as FMCK16, 8, and 4 are high. This count however, through the
use of inverters 12202, 12204 and due to the fact that the
carry input to the lowest bit is held high, is transformed
to the count of 2. In other words, the outputs A - ~F rise
and fall two counts in advance of the MUXA through MUXF signals.
Similarly if the line position were four counts or one step low,
FMCK4 would be high, FMCK8 would be low, FMCK16 would be low
.
and FMCK32 would be high, producing a total count of 36.
However, since FMCK16, 8 and 4 are inverted, it is evldent that
the count to be added is 58. Since the count of 58 is six less
than the cownt of 64, it is apparent that ~A t~rou7h EF rises
six counts later than the respective MUXA through MUXF driving
signals. Likewise as the FMCK4 through 16 bits vary between
counts o~ 12 and 52, the output E A through ~ F varies from
; 218
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~4~7
leading by 18 counts to lagging by 22 counts. The lead or lag
is effected in four count increments; therefore, a lead would
be by 2, 6, 10, 14, 18 or 20 counts, and a lag would be by 6,
10, 14, 18 and 22 counts. The two count bias in the downward
direction is needed to compensate for the bias put into the line
position analysis count; that is, the average bias for the line
position analysis circuitry is two counts high.
The BLKS EN 2 signal goes high at the beginning of
summation count (i.e. counter 9003, 9004 plus the FMCK bits) of
20 and low at the beginning of summation count 44. Thus, during
six lines per inch operation, the set signal at flip-flop 12314
is high and permits the flip-flop to toggle. The first time C,
E E and ~ are all high, which time coincides with the
beginning of summation count 20, gate 12312 goes high at TPA.
This sets flip-flop 12314, causing the BLKS EN 2 signal to go
high. It remains`high until the TPA of the~first count where
C, ~ D, and ~ F are all high,;which occurs at the beginning
of summation count 44. (During three lines per inch operation
the 6 LPI signal is low, causing flip-flop 12314 to remain set).
BLKS EN 2 thus remains high for~approximately 24 counts, beginning
with summation count 20 and ending wlth summation count 44. If
; the line position analysis circuit indicates a center condition,
this means that the BLKS EM 2 slgnal is centered ln tlme about
the vertical scan. ~ ~ ~
During six lines pe~r inch operation flip-flop 12317 is
also permitted to toggle. At the 1rst count in which E c FE
and ~ ~ are high (that is, summation count 36), gate 1231S sets
.1 '
219
$:
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'
:3L(1~9~7
~lip-flop 12317. Since all input signals to gate 12319 are high
at this time, th~ ~RI~{ output signal from that gate goes h~gh.
~ <.. ~
WRI~I stays high until ~ A,l-~, and d F all go high at gate 12316.
~ The first time this happens is at the beginning of summation
count 56. Gate 12316 resets flip-flop 12317 and causes signal
WRI~ to go lowO During three lines per inch operation the 6LPI
signal is low, keeping WRINH high, provided none of the other
inputs to gate i2319 go low.
There are two other conditions which cause WRINH to go
0 low. The first situation occurs if for any reason the amplitudes `
on two of the SPL NUM ~1~ ~2 buses are the same. Under such
conditions, all of the bus lines SPL, NUM, ~ 1 and ~ are high,
causing WRINH to go low. The second situation occurs if the
hand wrLtten or 7B font is chosen. In this case the CTR sIT 2
.
S signal is low, keeping the WRINH signal low.
lt is to be noted that the BLKS EN 2 signal is of
sufficiently short duration that it can be advanced or retarded
the full 20 counts in each direction without extending into the
adjacent column scan period. The write enable or WRINH may
0 extend into the following vertical scan interval if a lag of
20 counts is generated or detected in other words if the image
wcre up to 20 counts low. This however is acceptable since by
: .,
the time the image is centexed in the mask, the beginning of the
'
follow~ng scan interval is in effect.
In order to maintain proper operation of the vertical
position analysis circuit or the line position analysis circuit,
` the BLKS EN 1 signal must be turned on no earlier than MUX count 2
: :`
220
. ~ ,,
.
: ~ -, , ~, ,
.
~04~9~q~7
and turned off no later than MUX count 62. Therefore, if more
than a four count advance is generated, BLKS EN 1 must go high
at MUX count 2 rather than under the control of the summation
count. The circuit for effecting this includes gates 12303-12306.
If FMCK8, 4, or 16 are low, gate 12304 goes high. I~ FMCK32 is
also high, gate 12305 is enabled, disabling gate 12306 but
enabling gate 12303. This primes gate 12301. When MUXD and MUXF
are high, gate 12301 is driven low and flip-flop 12307 is set.
With the assumed conditions of FMCK32 high and either FMCK8, 14 or
16 low, a summation count of less than 28 is generated. Under
these conditions the BLKS E~ 1 signal is prevented from turning
on before MNX count 2.
If FMCK32 is high or FMCK32 is low and all of FMCK8,
14, or 16 are high, gate 12306 is low. Gate 12301 is disabled
while gate 12306 is enabled, allowing the ~ A, ENSTP, ~ C, and
signals to proceed through gate 12309 and cause gate 12306
to go high. This high-going transition clocks the high at the
. ~ .
data input of flip-flop 12307 to set that flip-flop.
The ENST ~enable startj and E~STP (enable stop) signals
are generated at multiplexer 12~06. In the read mode (LDFT high),
ENST corresponds to B and~E~STP corresponding to ~D~ Thus,
at summation count 7, gate 12308 is enabled, setting flip-flop
12307 and causing BLKS EN 1 to;go high. Gate 12309 is enabled
~; .
when ~ A, ~ D,E E and ~ F are~high, which correspond to summation
count 57, at which time blacks enable 1 flip-flop 12307 is
reset by a low signal. Since the summation count is generated
~,,
~ from the summation of the MUX counter ~Fig. 90) and the line
. ~ , .
?~ 221
. .
;
~C~4~ 7
position adjus-t circuits (FMCK bits), the tail end of the
BLKS EN 1 signal could extend beyond MUX count 61 if it were
retarded by eight counts or more. In this case, at MUX61 time,
gate 12311 is enabled, producing a low output which is fed out
through again to reset flip-flop 12307.
In the read mode, BLKS EN 1 is on for 50 counts of
the MUX coun-ter; however, during load format time BLKS EN 1 is
high for only 38 counts, coming on at count 13 and going off at
count 51. The change from 50 to 38 counts is performed at
multiplexer 12206. During load format the LDFT signal goes low
causing the ~ D signal to be fed through as the ENST signal and
the ~ B signal to be fed as the ENSTP signal.
;
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CONCLUSION
The system as described is extremely flexible with
respect to its ability to read data presented in a variety of
formats and in its ability to re-position a document so as to
properly center data in the photo-diode array. The system as
disclosed is capable of reading a field eight inches wide
starting one quarter of an inch from the left hand edge of a
document page. A machine printing pitch of 10 characters per
inch can be accommodated, with lesser pitches being easily
read. Line spacing of six lines per inch or greater can also
be accommodated. Documents are read line by line with the
full height of the document capable of receiving data~
A variety of paper stock thicknesses and weights
can be accommodated as can a variety in the reflectivity of
the stock and ink.
While we have described and illustrated specific
embodiments of our invention, it will be clear that variations
of the details of construction which are specifically illustrated
and described may be resorted to without departing frcm the true
spirit and scope of the invention as defined in the appended
~ claims.
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