Note: Descriptions are shown in the official language in which they were submitted.
01 Patent Applicat.ion of
02 Michael H. Smi-th
03 REVERSE. TAB CO~TROL SYSTEM
04 FOR TYPEWRITER
0~
06 BACKGROUND OF INVENTION
07 Field of Invention
08 This invention relates to typewriters, particularly
09 to a typewriter having tabulation (tab) controls. More
:10 particularly it relat~s to such a typewriter wherein reverse as
11 well as orward tab capabilities are provided.
12
~13 Description of Prior Art
14 Heretofore most typewriters contained tab controls for
rapidly and automatically ad~usting -the relative posi~ons of
:16
~17
18
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01 the printing mechanism (type bars or print head) and
02 the platen. In typewriters wit~ Eixed print heads
03 or -typebars, the platen was moved with respect -to
04 printing mechanism, and in typewri-ters with fixed
05 platens, the printing head ~a ball or a spoked and
06 riml ss "daisy" wheel) was moved wi~h respect to the
07 platen. For purposes of facilitating discussion,
08 the operation will be detailed with reference to the
09 latter type oE machine (the print head moves and the
platen is Eixed), but the former type of machine
11 (print mechanism is fixed and platen moves) should
12 also be considered as an included method of tab
13 operation.
14 The tab feature is useful for enabling a
typist to effect rapid and repetitive movements of
16 the printing mechanism to a plurality of different
17 horizontal positions along a line on the paper or
18 other recording web. In mechanical typewriters, the
19 tab stop positions were usually stored by
positioning mechanical pawls to stop movement of the
21 platen at spaced horizontal locations, where
22 desired. In electronic typewriters, the output of
23 the keyboard consists of electronic signals which
24 are processed in an electroni.c data processing
system within the typewriter to generate suitable
26 control signals for driving solenoids and step-or
27 servo-motors to cause the typing mechanism to print
28 selected characters and e~fect other operations;
29 here the tab stop positions usually were stored in
an electronic memory and the carrier was moved to
31 the tab stop positions by means of a servomechanism
32 under control of the electronic data processing
33 system.
34 In most typewriters, the tab system was
of the forward type only, i.e., the tab mechanism
36 was able to move the printing mechanism only to the
37 right with respect to the platan. This is
38 2 -
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01 disadvantageous in situations w~ere a typist must
02 type, for example, a single column of characters.
03 After typing a line of the column, to type the next
04 line the typist must return the print head to the
05 first character of the column. To do this, the
06 typist must choose one of two awkward alternatives.
07 The first alternative is to reset the left margin
08 control to the first character oE the column of
09 characters before typing the column. However this
is an ~wkward operation and the original margin must
11 be located and restored when typing of the column is
12 completed. Alternatively, the typist can effect a
13 carrier return, causing the carrier to move all the
14 way to the left, and thereafter repeat tab until the
carrier advances to the desired position; this is
16 also awkward and inefficient.
17 To avoid these drawbacks, typerwriters
18 recently have appeared with a reverse-tab
19 ~apability. In these typewriters, when a
reverse-tab key was pressed, or when the regular tab
21 was actuated in a certain manner, different rom the
22 regular forward-tab method of actuation, the carrier
23 would move to the left with respect to the platen,
24 i~e., to the next tab stop at the left of its
current position. The reverse-tab feature greatly
26 facilitated typing oE columnar material by
~7 eliminating the above drawbacks.
2~ As an added feature, some typewriters
2g have also provided an automatic line indexing or
platen rotation feature upon opera-tion o the
31 reverse tab key. In this feature, when the reverse
3~ tab key was operated and the carrier moved to the
33 left with respect to the platen, the platen would
34 also index, i.e., rotate by an angle equivalent to
one line space so as to cause the next line position
3~ on the paper to appear at the current typing
37 position. This made it even easier to type columnar
38 - 3 -
D3~3
01 material since it eliminated the need for the typist
02 to manually advance to the next line space aEter a
03 reverse-tab operation.
04 However the above combination o~
05 indexing or line spacing with reverse tab was
06 disadvantageous when several columns of material
07 were being typed since this requires that the
08 carrier be moved to a second or even further-left
09 column ~rorn a curren-t typing posi-tion after each
line is typed. The typist was not able to do this
11 easily by repetitively reverse tabbing because every
12 reverse-tab also caused an index; thus the correct
13 position Eor typing the next line would be lost upon
14 the second reverse-tab actuation. Thus in order to
effect a reverse-tab movement to a second or
16 subsequent column, the typist had to repetitively
17 reverse tab to the desired column and thereafter
18 adjust the platen so that the correct line on the
19 paper was at the printing position. Alternatively,
the typist could still effect a carrier return to
21 the left margin and then forward tab to the desired
22 column. However this did not take advan-tage o~ the
23 machine's reverse-tab capability and was also
2~ difficult and time consuming.
Accordingly, one object of the present
26 invention is to provide a typewriter with a
27 reverse-tab feature whereby reverse-tab operations
28 to the second or Eurther columns of typing material
29 to the left of the current posi-tion can be effected
without adjusting the platen. Another object is to
31 provide such a typewriter with a more efficient
3~ reverse-tab operating sequence~ A further objec~ is
33 to provide an electronic typewriter with a novel
34 reverse-tab opera-ting feature.
Thus, according to one embodiment of the
3~ present invention, there is provided a tab control
37 system for a typewriter comprising a keyboard
38 - 4 -
~3~3
01 con-taining character keys; -type elements and a
Q2 carrier therefor, mechanical striking apparatus
03 attached to the carrier and capable of striking the
04 type elements against a platen in accordance with
05 characters selected on the keyboard; the carrier,
06 the mechanical striking apparatus, and the type
07 elements being arranged to move axially with respect
08 to the platen, the carrier also being arranged to
09 move a predetermined distance .in a predetermined
direction with the striking of any character of the
11 type element apparatus against the platen. ~le
12 keyboard includes a tab set apparatus for manually
13 presetting a plurality of tab stop positi.ons of the
14 carrier with respect to the p~aten, a tab clear
apparatus for clearing any of -the plurality oE the
16 tab stop positions when set, and a tab actua-ting
17 apparatus responsive to a first kind of manual
18 actuation thereof for moving the carrier to any of
19 the plurality of preset tab stop positions. The
system includes tab control apparatus for moving the
21 carrier from its present posi.tion to the closest
22 preset tab stop position in t:he predetermined
23 direction upon each rnanual actuation of the tab
24 actuating apparatus, the tab control apparatus also
~5 being arranged to move the carrier to the closest
26 predetermined tab position in a direction opposite
~7 to the predetermined direction and for rotating the
28 platen through a predeterminad angle so as to cause
29 any type-receiving medium positioned around the
platen to move to a lower line position with respect
31 to the carrier, upon a second kind o manual
32 actuation of the tab actuating apparatus, and or
33 moving the carrier to the closest predetermined tab
34 position in the opposite direction and without
rotating the platen, upon each manual actuation of
36 the tab control apparatus directly after the second
3l kind of manual actuation thereof.
38 - 5 -
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01 Fur-ther objects and advantages will
02 become apparent from a consideration of the ensuing
03 descrip~ion and the accompanying drawings.
04 DRAWINGS
05 Fig. 1 illustrates an electronic
06 typewriter according to the invention.
07 ~igs. 2A, 2B and 2C are diagrammatic
08 illustrations of a sequence of reverse tab
09 operations according to the invention.
Figs. 3A, 3B and 3C are a t~ree-part
11 flow chart showing the sequence of reverse-tab
12 operations according to the invention.
13 Fig. 4 is a block diagram of an
14 electronic system used in the typewriter of the
invention.
16 FIG. l--ELECTRONIC TYPEWRITER
17 In Fig. 1, an Electronic Typewriter 10
18 according to the invention comprises the usual
1~ Keyboard 12, Platen 14, Print Wheel 16, and Movable
Carrier 18 for Wheel 16. Pri.nt Wheel 16 is a common
21 spoked and rimless prin-t or "daisy" wheel: it has a
22 plurality of radial spokes or petals, each
23 containing a respective character of the keyboard.
24 When any character is typed, Wheel 16 is rotated so
that the desired character petal is upright and then
26 a han~er (not shown) strikes such petal over an
27 inked or carbonnsd ribbon 20 onto a paper or other
28 wri-ting medium (not shown) which is fed over Platen
29 14.
Keyboard 12 contains the usual character
31 and control function keys, some of which are
32 indicated, and also contains the following keys of
33 particular interest: A Tab Set Key 22, a Tab Clear
34 Key 24, and a Tab ~ctuating (Tab) Key 26. Tab Clear
Key 24 and Tab Key 26 are each depressible to either
36 a shallow position or a deep position for purposes
37 described subsequently. Typewriter 10 also includes
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93
01 a Control C:ircuit 28 which controls the Eunctions
02 and operations o Typewriter 10 in response to
03 actuation of character and control keys on Keyboard
04 12. Principally, Circuit 28 con-trols the operation
05 o Print ~heel 16, Platen 14, and Carrier 18.
06 More specifically, when a key on
07 Keyboard 12 representing a selected character is
08 depressed, a unique electronic signal representing
09 that key will be coupled to Control Circuit 28 which
will in turn generate appropriate signals to cause
11 Print Wheel 16 to rotate so that a petal thereof
12 with the selected character is upright. Circuit 28
13 will also cause ~he hammer to strike that petal
14 against Platen 14 via Print Ribbon 20 so as to
imprint the character on the paper and also move
16 Carrier 1~ to the right a distance equal to one
17 character pitch or one space, either before or after
18 the hammer operates, so that each subsequent
19 character will be typed one space to the ri~ht of
the previous character.
21 FIG. 2 --REVERSE TAB OPERATION
22 Prior to describing the reverse tab
23 operation according to the invention, the forward
24 and prior-art reverse tab mocles of operation will be
described in order to facilit:ate an understanding of
26 the inventive reverse tab operation.
27 Forward Tab
28 Referr:ing to Fig. 2A, assume that a
29 typist desired to t~pe a pluralit~ of columns on a
paper, such as columns 30 and 32 indicated. Each
31 column is composed of successive rows of four
32 numbers each for purposes of example. The typist
33 set the first tab stop by moving Carrier 18 to the
34 horizontal position indicated at "TSl" (Tab Stop 1)
and thereafter depressed Tab Set Key 22. A tab stop
36 was thereupon set at this position. Then Carrier 18
37 was moved to position TS2, the position of the first
38 - 7 -
01 charac-ter in column 32. The typist again depressed
02 Tab Set Key 22, thereby setting a second tab stop at
03 this posit.ion. Thereafter to type columns 30 and
Q~ 32, the typist first pressed Tab Key 26 to cause the
05 carrier to move immediately and continuously from
06 any position left of column 30 to TSl, the carrier
07 stop position for printiny the ~irst charac-ter in
08 column 30. After the characters oE -the first row of
09 column 30 were typed, the typist again depressed Tab
Key 26 to effect an immediate and con-tinuous
11 movement of Carrier 18 to TS2, the carrier stop
12 position for printing the first character in column
13 32.
14 The typist -then pushed the carrier
return key, causing the carrier to move to the left
16 margin, which would be somewhere to the left of
17 position TSl, and also causing the platen to rotate
18 one line space so as to move the paper up one line.
19 The carrier was now in posit:ion to print the second
line of columns 30 and 32. The typist again
21 depressed Tab Key 26 to move Carrier 18 to position
22 TSl, typed the second row of column 30, pushed Tab
23 Key again to move ~he carrier to position TS2, and
2~ then typed the characters in the second row of
column 32. The.reafter the carrier was in position
26 to print in the ~ext character space to the right of
27 the last character ("1") of the second row of column
28 32, as indicated by the next print position (NPP)
29 indicator arrow 3~.
Prior Art Reverse Tab
31 If the typist were typing only a single
32 column, such as column 32, and the typewriter had
33 the prior-art reverse-tab-wi-th-index capability, the
34 typist was able to return the carrier to position
TS2 and move the paper to the next line, as
36 ind.icated by path 33 in Fig. 2B, by either
37 depressing Tab Key 26 to a deep position (D) rather
38 - 8 -
r
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01 than the usual shallow position (S~, or by actuating
02 a separate reverse tab key (not shown). Carrier 18
03 automatically moved backward continuously or
04 repeatedly backspaced to the next tab stop position
05 (TS2), and Platen 14 rotated one line (or several
06 lines if line spacing was so set), so that the print
07 posi-tion indica-tor moved to the left and down (line
08 36), to a position one lin~ under the first
09 character in the second row of column 32. Thus a
third row of characters (not shown) could be typed
11 in column 32 without returning Carrier 18 to the
12 left margin and then forward tabbing one or more
13 times in order to move the carrier to position TS~
14 and one line below the last line typed.
However, if the typist were typing two
16 or mora columns, it was not possible, using the
17 prior-art reverse tab with index feature, to move
18 the carrier easily to the first character position
19 in the third row of first colurnn 30 since each
subsequent reverse-tab operation would cause the
21 platen to index, so that -the print posi-tion
22 indicator would move to the fourth line position
23 (not shown) of column 30, thus requiring additional
2~ adjustments of the platen, or non-use of the
reverse-tab feature when plural columns were being
26 typed.
27 Reverse Tab According to Invention
2~ As indicated in Fig. 2C at 35, if Tab
29 Key 26 is shallow depressed after the first deep
depression thereo, the carrier will still rnove
31 leftward to the next left tab stop position TSl but
32 Platen 14 will not rotate. Thus the next print
33 position indicator 3~ will be in the correct
34 position to type the next row in column 30--i.e.,
one line under the first character in the second row
36 as shown. Hence, a typist could effect proper
37 reverse movements of the carrier very easily when
38 _ 9 _
~:~~3~3
01 typing two columns by merely depressing Tab Key 26
02 -twice, the first depression being a deep depression,
03 tnereby moving Carrier 18 back to TSl and one line
04 down. If rnore than two columns are being typed, the
05 typist need merely depress Tab Key 26 a sufficient
06 number o additional times to reach the first column
07 being typed. The correct line and tab stop will
08 automatically be reached at any column withou-t the
09 need to effect a carrier return or rotate the platen
in a separate operation.
11 The reverse tab moves have been
12 described in the foregoing paragraphs and
13 illustrated in Figs. 2B and 2C (by broken lines 36
14 and 38) as occurring directly upon a deep depression
of Tab Key 26. However, in actuality, in a current
16 commercial embodiment oE the invention, any
17 depression of Tab Key 26 (shallow or deep) will
18 cause a forward tab move (if possible) which begins
19 immediately. If the depression of Key 26 is a deep
one, after completing the forward tab move the
21 reverse tab moves described and illustrated will be
22 executed, i.e., the carrier will rnove directly back
23 to and through its posi-tion at start oE the forward
24 move. The overall results b~eing the same, the
forward tab move and the corresponding return part
26 of the reverse tab moves have not been illustrated
27 in Figs. 2B and 2C in order to simplify the drawing.
28 To review, according to the invention a
29 deep depression of Tab Key 2~ will effect a movement
of Carrier 18 ending at the next preceding tab stop
31 position (to the left), coupled with a rotation of
32 Platen 14 to the next line. ~ach subsequent shallow
33 depresion of Tab Key 26 will move Carrier 18 to the
34 next left tab position, without rotating the
platen. (Subse~uent deep depressions of Tab Key 26
will cause Carrier 18 to move two tab stops to the
37 left, without a platen rotation. This operation is
38 - 10 -
33
01 not described infra for purposes of facilitation of
02 explanation.)
03 The normal mode of operation upon a
04 shallow depression of Tab Key 26 is a forward
05 (righ-tward) movement of the carrier to -the next tab
06 stop. This normal mGde can be restored (af-ter any
07 reverse movemen-t d~le to a deep depression of Tab Key
08 26) by operating any character key, the space bar,
09 or almost any other function key.
FIGS. 3A and 3B--FLOW CHART
,
ll Figs. 3A and 3B depict the various
12 operations which occur within Control Circuit 28 to
13 effect the reverse tab mode of operation. The
14 various blocks within Figs. 3A and 3B depict
individual operations which occur within Control
16 Circuit 28 and the order of progression of the
17 blocks depicts the sequence of these operations, in
18 accordance with well-known flow chart usage.
19 Contro:L Circuit 28 includes a microprocessor which,
in accordance with the usual prac-tice, makes
21 continuous repetitive checks or interrogations of
22 various conditions in the machine and, depending
23 upon the state of such conditions, initiates or
24 ~kips appropriate ~ubroutines. The flow chart
illustrates operations relevant to a subroutine
26 initia~ed when Circuit 28 detects that T~b Key 26
27 (Fig7 l) has been depressed.
2~ Fig. 3A--First Pass--Reverse Tab Key Entry
29 rrhe reverse tab mode is ini-tiated when
Key 26 is deeply depressed. Two things thereupon
31 occur to effect a Reverse Tab Key Entry, as will now
3~ be discussed.
33 Deep depression of Key 26 causes a Key
34 Waiting Flag and Repeat Terminal Flag to be set.
These Elags correspond to binary cells in a memory
36 array or Status RAM 400 of Fig. 4 (described infra)
37 which indicate th~ status of various condi-tions or
38
3~393
01 components o~ the machine. Depression of any key on
02 Keyboard 12 causes the Key Waiting Flag to be set
03 directly by a signal on an output line 403,
04 indicating depression of a key (generally) on
05 Keyboard 12. Also, information corresponding to -the
06 iden-tity of the key depressed is provided at the
07 output of a keyboard Encoder or ROM 402 of Fig. 4
08 (described infra and forming part c)f a keyboard
09 Input Interface 401). Deep depression o Tab Key 26
moves a common bail 404 (Fig. 4), activating a
ll mechanical coupling 406 which will in turn close a
12 single-pole-single-throw momentary switch 408. This
13 will ground and activate a Repeat Terminal input
14 lead 409 connected directly to a Repeat Terminal
stage or flag in Status RAM 400 which is immediately
16 set, as a result. Normally the Repeat Terminal
17 input lead of RAM 400 is biased a-t a positive
18 voltage (non-activating) by Positive Source 410 and
19 Resistor 412. The Repeat Terminal input is used
since it is a convenient method of effecting two
21 modes of operation (forward and reverse tab) with a
22 single Tab Key 26.
23 Box 44 Prior to describing the first operation,
24 it will be noted here that the above-mentioned flags
are periodically checked or interrogated, part of a
26 rou-tine identified by a circular (connector) box 44,
27 labeled "Next Key Routine." Normally, Control
28 Circuit 28 is in this idling routine in which
29 interrogations of various ~lags or conditions in
S-tatus RAM 400 are made. These will not ~e listed
31 here except insofar as relevant. After completing
32 any operation, the machine returns to its idling
33 routine so that Box 44 represents a significant
34 point in the flow chart.
Box 46 In its idling routine, Control Circuit
-
36 28 checks the Key Waiting Flag in RAM 400, as
37 indicated by diamond (decision) Box 46. Since the
38 - 12 -
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01 Key Wai~ing Flag has been set, as described above,
02 the Yes output oE Box 46 will be followed.
03 Box 48 Next, itl response to the presence of the
04 Key Waiting Flay, a data number (code) representing
05 depression of Tab Key 26 and provided at the output
06 oE ROM 402, will be read and stored in a
07 First-In-First-Out (FIFO) Register which is Register
08 A in a Data Storage RAM 414, described inra. The
09 Key Waiting Flag will be cleared at the time of read
out.
11 Box 50 I'o indicate that FIFO Register 414A is
12 occupied, a FIFO-Empty Flag in Status RAM 400 is
13 cleared, as shown by Box 50.
14 Box 52 Next, as indicated by this Box 52, the
FIFO-Emp-ty stage of Status RAM 400 will be
16 interrogated. Since this stage was just cleared in
17 the operation of Box 50, the Mo output of Box 52
18 will be followed.
19 Box 54 Si.nce testing of the FIFO-Empty Flag has
~0 shown tha-t there is at least one Key (code) stored
21 in the FIFO (Box 52), the ne~t key in the FIFO,
22 regardless of its identity, will be transferred to a
23 ~ew Key Regis-ter 414I; the oldest and each
24 succeeding Key code will be successively
~ransferred, identified, and processed. Thus, in
26 its turn, the Tab Key data code will be transferred
27 from FIFO Register 414A, via an Accumulator 416, to
28 New Key Register 414I, as indicated in Box 54.
2g Also, a Repeat Elag in Status RAM 400 will be
cleared if set. The Repeat flag differs from the
31 Repeat Terminal Flag which was set by deep
32 depression of Tab Key 26, and is used to cause the
33 machine to perform ~he Repeat function. The Repeat
34 Terminal Flag merely indicates that the Repeat
Terminal of RAM 400 has been activated, i.e., Switch
36 408 has been closed.
37 Box 56 Next a determination is made in Box 56
38 - 13 -
, .. . ..
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01 as to whether the data transferred to New Key
02 Register 414I represents the Tab Key. The
03 determina~ion in Bo~ 56 is made to determine if the
04 reverse tab mode should be cleared if the tab key
05 code is not present in New Key Register 414I, as
06 more fully discussed below.
07 Box 58 Next, as indicated in Box 58, a two-part
08 FIFO-pointer Register 414K having a first part 414Kl
09 controlling the order of information readout rom
FIFO Register 414A, is updated to account -for the
11 transfer that occurred in Box 54. Another part of
12 the FIFO-pointer register 414K2 controls the
13 position of Register 414A at which input information
14 i5 stored. The address information in these two
parts of Register A14K controls the state of the
16 FIFO-Empty Flag in ~tatus RAM 400. IE that
17 information is identical, the FIFO is empty and the
18 ~IFO-Empty Flag is set, but is cleared upon a
19 subsequent key-entry. Thus, as part of ~ox 58 the
pointer contents are compared in known fashion and
21 -the FIFO-Empty Flag updated accordingly.
22 Box 60 Other preliminary operations, not
23 relevant to the Reverse Tab operation, are made
24 after Box 58, where the flow chart route for the
actual Tab routine begins, as indicated generally by
~6 the Key Decode Connector Box 60 at the bottom of
27 Fig. 3A, Part I and at -the top of Fig. 3B, Part II
28 of the Flow Chart. The Key Decode includes
29 ssgregation of function codes in known fashion.
Box 61 The next operation and the first of
31 Fig. 3B, indicated in this bo~, is one of the
32 routi.ne checks or interrogations performed by
33 Circuit 28. This operation is a decision which
34 determines whether the Key Code in New Key Register
414I is a non-print key. If not, this indicates
36 that the Key Code represents a printable character,
37 so -that the No output is followed and the printable
38 - 14 -
~3~3
01 Key is processed, as indicated in predefined process
02 Box 61A. Since the Tab Key is a non-printable or
03 "func-tion" Key, the Yes output is :EolLowed to Box
04 62. (In actuality, the decision of Box 61
05 determines whether the Key Code is greater than 91
06 since all printable Key codes have values less than
07 92 and all function Key codes have values greater
08 than 91.)
09 Box 62 The operation indicated in this box, is
also one of the routine interrogations performed by
11 Circuit 28. This operation is a decision which
12 determines whether a function Key code found to be
13 in the New Key Register 414I is the Tab Key code.
14 If not, the No output of Box 62 will be followed
and, as indicated by Box 6~, further tests to
16 iden-tify and process the function code are
17 performed, but are not relevant here. If the key to
18 be processed is the Tab ~ey, the Yes output of Box
19 62 will be followed to Box 66
Box 66 In this box, Circuit 28 determines
21 whether the left margin setting (a stored count of a
22 number of spaces from the lefl end of Platen 1~,
23 which count is initially preset automatically or
24 otherwise programmed by the typist) is greater than
the carrier's present position, i.e., is the number
26 of spaces from the left end of Platen 14 to the left
27 margin greater than the number of spaces from the
28 left end to the present position of Carrier 18? If
29 the left margin setting is greater than the carrier
present posit.ion, the carrier is outside the usual
31 text area--in other words, to the left of the left
32 margin--and the Yes output of Box 66 will be
33 followed, but if the carrier is to the right of the
3~ left margin, the No output of Box 66 will be
followed.
36 Box 68 Assuming the carrier is to the let of
_
37 the left margin so that the ~es output of Bo~ 68 is
38 - 15 -
~3~3
01 followed, the next operation, illustrated by Box 68,
02 is to set a Carrier Desired Posi-tion Register 414F
03 to the stored value for the left margin position.
04 ThereaEter, as illustrated by Box 70, the machine
05 makes a forward (rightward) move to the left margin.
06 When the position o Carrier 18 is to
07 the left oE the left margin, actuation of Tab Key 26
08 will cause Carrier 18 to move rightward to the left
09 margin, and no reverse move will -take place, even if
Tab Key 26 is deeply depressed, and any tab s~ops
11 set to the left of the left margin being ignored.
12 This mode of operation is provided as it would be an
13 undesirable and probably mistaken mode of operatio~
14 to try to move the carrier to any tab stops which
might be set ou-tside the left margin.
16 Box 44 Bis After the forward move to the left
17 margin (Box 70) the machine returns to its normal
18 idling procedure or Next Key Routine, as illustrated
19 by connector Box 44 of Fig. 3B, which connects to
Box 44 o Fig. 3A. The machine will Eollow the flow
21 chart and ultimately reach connector Box 130 of
22 Fig. 3C, in which a user error indication i9
23 provided. This sequence will not be detailed.
24 Box 72 If the decision in Box 66 is ~o, i.e.,
the carrier is not to the left of the let margin,
26 the next step i9 to sat a Margin Release Flay, as
27 indicated in Box 72. Setting a Margin Release Flag
28 involves setting a regist~r (not shown) to a certain
29 state which will enable forward tab moves to be made
to and to the right o the right margin without
31 operating the margin release key.
32 Box 74 The next step, illustrated by Box 74, is
33 to determine whether the Reverse Tab Mode Flag has
34 been set. The Reverse Tab Mode Flag, also in Sta~us
~M 400, is set after the reverse tab mode had been
36 en~ered. If Tab Key 26 has been deep-depressed for
37 the first -time, the machine will not yet be in the
38 - 16 -
. .
3~33
01 Reverse Tab mode so that the Reverse Tab Mode Flag
02 will not have been set and the No output of Bo~ 74
03 will be followed. However, if the machine has
04 previously entered the Reverse Tab mocle, the flag
05 will be in the set state and the Yes output oE Box
06 74 will be followed.
07 B 76 Since the Reverse Tab Mode Flag has not
08 yet been set, the No outpu-t of Box 74 is followed.
09 The next operation is a decision (Box 76) to see i
the Repeat Flag has been set. Since only the Repeat
ll Terminal Flag has been set thus Ear (Box 42), the No
12 output of Box 76 will be followed to Box 77.
13 Box 77 A forward tab move is then executed, as
14 indicated in Box 77, to the next tab stop to ~he
right of the carrier's present posi-tion, or if there
16 i5 no such tab stop, the carrier will proceed to the
17 right margin. When the forward tab move is
18 completed, the machine has cornpleted its first pass
l9 of the flow chart and continues to the Next Key
Routine, as indicated by Box 44, which connects with
21 that same Box at the top oE Fig. 3A.
22 Fig. 3A--Second Pass--Repeat Flag Tests
23 Box 46 Bis Returning to Fig. 3A, where the
24 operation~ continue at the output of Box 44, the
second pass through Fig. 3 Part I of the flow chart
26 is made, this time ~or performing various Repeat
27 Flag tests. A decision is again made in Box 46 as
28 to whether the Key Waiting Flag has been set. The
29 Key Waiting Flag is no longer set, since the Tab Key
code awaiting entry was delivered from ROM 402 to
31 the FIFO (Box 48) at which time the Key Waiting Flag
32 was reset, as mentioned earlier; and providing the
33 typist has not depressed further keys, as will be
34 assumed for purposes of this description; so that
the ~o output of Box 46 is followed to Box 52.
36 Box 52 Bis Again the FIFO-Empty Flag is checked in
-
37 Box 52, but this time the decision will be Yes,
38 - 17 -
3~33
01 since the tab key was transferred from -the FIFO in
02 Box 54 and -the empty flag was set in Box 58.
03 Box 78 Next, as indicate~d in this box, the
04 RPpea-t Terminal Flag in S-tatus RAM 400 is checked.
05 This flag was a]ready set as previously described in
06 the introductory remarks concerning the Flow, so
07 that the Yes output of Box 78 will be followed.
08 Note that this flag can only be cleared upon the
09 typist's release of the deep depressed Tab Key 26.
Box 80 The Repeat-In Flag is then checked.
11 This flag is set when the Repeat Terminal Flag has
12 been recognized and processed. Since this has not
13 yet been done, the decision in Box 80 will be No.
14 Box 82 A short delay (20ms) is provided in Box
82 to allow termination o-F any transients resulting
16 Erom deep depression oE Tab Key 26 and activation of
17 Switch 408, thereby to prevent false triggering.
18 Box 84 The FIFO-Empty Flag is next checked.
19 Since this f].ag is now set, as explained in the
second discussion o~ Box 52 above, the Yes output is
21 followed.
22 Box 8 A check is again made of the Repeat
23 Terminal Flag. As explained above in the discussion
24 of Box 78, this flag is still set, so the Yes output
is followed. If not set after the delay of Box 82,
26 this indicates the Repeat Terminal Flag seen in Box
27 78 was caused by an unwanted transient signal.
28 _ox 87 Next, the Repeat Flag (indicating the
29 machine should repeat the key in the ~ew Key
Register) i~ set and the Repeat-In Flag (indicating
31 that the Repeat Terrninal Flag has been recognized~
32 is also set.
33 The sequence then proceeds agai.n through
34 connector Box 60 to Part II of the flow chart in
Fig. 3B through Box 62 tYes), Box 66 (No), Box 72
36 (No) to Box 76 again.
37 Fig. 3B--Reverse Tab Entry
38 - 18 -
~3~3
01 Box 76 Bis The Repeat Flag has just been set in Box
02 87, so that the Yes output of Box 76 is followed on
03 the second pass through the box, whereupon actual
04 entry oE the Reverse Tab Mode is begun.
05 Box 88 The next step (Box 88) is to set a Line
06 Feed Flag and a Reverse Tab Mode Flag (bo~h also in
07 Status RAM 400) to indicate that upon the nex-t
08 execution of a mechanical operation, a line feed
09 (rotation) of Platen 14 and a reverse tab opera~ion
should both be efected.
11 Returning to Box 74, if the Reverse Tab
12 Mode Flag were already set at the ~ime of the
13 decision in Box 74, the Yes ou~put of Box 74 would
14 be followed to the output of Box 88. This path is
taken when the machine is already in the Reverse Tab
16 mode, in which case the decision of Box 76 and the
17 flag setting of Box 88 would not be appropriate.
18 The Reverse Tab Flag would already be set and the
19 Line Feed Flag should not he set since a line eed
is desired only upon the Eirst reverse tab move and
21 according to one main aspect of ~he invention is
22 omitted thereafter.
23 Box 90 Next, the Repeat Flag (in Status RAM
24 400) is cleared, as indicated in this box, in order
to prevent continuously repeated reverse tab
26 operations. Also the Margin Release Flag, set in
27 Box 72, will be cleared to prevent any moves through
28 the margins on subsequent key inputs.
29 Locating Tab Stop
Box 92 Next, as illustrated in Box 92, a Tab
31 Pointer Register, which is present as Register H of
32 Data Storage R~M 414 tFig. 4), is set to address the
33 highest address cell in a Tab Stop Register
34 (Register G of RAM 414). The Tab Stop Register
stores the positions or "Stops" along Platen 14 to
36 which Carrier 18 will advance on -tab moves. Tab
37 Stop Register 414G has, in the present embodiment,
38 - 19 -
01 sixteen seven-bit cells for storing previously set
02 tab stops (from left to right) along the printing
03 line. In the operation of Box 92, the tab pointer
04 is set to address the highest-address cell in
05 Register 414G, i.e., the cell w~ich would store the
06 rightmost tab position i all sixteen possible tab
07 stops were se-t.
08 More particularly, when tab settings are
09 made, they are supplied to the sixteen cells of Tab
Stop Register 414G in order of their numbered space
11 positions along Platen 14, with ~he leftmost tab
12 stop setting being supplied to the cell with ~he
13 lowest address in Register 414G, the next left tab
14 stop setting to the cell with the next higher
address, and so on. If less than the sixteen
16 possible tab stops are set, the cells without a tab
17 stop will automatically be supplied with a reading
18 of 127, which is at least one higher than the
19 maximum tab stop setting position possible for a
machine set to 12-pitch (12 charact~rs per
21 horizontal inch) and having a writing line of 10.5
22 inches. In Box 92, Tab Point:er Register 414H is set
23 to address t~e cell with the highest possible
24 address as a first step in locating the closest tab
stop to the left of Carrier ].8. The tab stop cells
26 are addressed and checked in reverse order, ~rom
27 highest address to lowest, in oraer to locate such
28 closest-left tab stop.
29 Box 94 Next, as indicated, a decision is made
to determine whether the carrier's presen-t position
31 (stored in a Carrier Present Position Register 414D)
32 equals the setting in the cell addressed by -~he Tab
33 Pointer Register. If the decision is Yes, the
34 currently-addressed c811, which is the
maximum-address cell of Tab Stop Register 414D,
36 contains a valid carrier stop setting ~less than 127
37 for a machine set to 12-pitch), indicating that all
38 - 20 -
. `'.
33
01 sixteen possible carrier stop settings have been
02 made, and the carrier is presently at that stop
03 setting, which is the rightmost tab stop. If the
04 d~cision is No, there was either no tab setting in
05 the maximum-address cell, i.eO, the maximum-address
06 cell i5 set to an impossible carrier position (127),
07 or the carrier is to either side of the set-ting in
08 the maximum address cell.
09 Box 96 Assuming the No output o~ Box 94 is
followed, i.e., the carrier is to either side o the
ll set-ting of the maximum-address cell or there is no
12 tab stop in the maximum-address cell, a decision
13 will next be made (Box 961 to determine whether -the
14 carrier's present position is less than the setting
in the cell addressed by the Tab Pointer Register,
16 which i5 still the maximum-address cell. If the
17 decision is No, the carrier is to the right of
18 position in the address cell, which cell has been
19 set with a valid carrier position. Therefore, as
indicaked by connection Box 98, the closest tab stop
21 to the left o~ the carrier has been ound.
22 If the decision in Box 96 is Yes, i.e.,
23 the carrier's present position is less than the
24 position in the cell addressed by the Tab Pointer
Register, this indicates that the carrier is
26 somewhere to the let of the maximum tab stop
27 setting in the Tab Set Register.
28 Box 100 Assuming the carrier is to the lef~ of
29 the setting in the cell addressed by ~he Tab Pointer
Register (Yes rom Box 98), or if the carrier's
31 present position is equal to the position in the
32 cell addressed (Yes from Box 94), next a decision
33 will be made (Box 100) to determine whe-ther Tab
34 Pointer is addressing the minimum-address cell of
the Tab Stop Register. In the present round the Tab
36 Pointer could not be at such minimum-address cell
37 since it has just been set to he maximum-address
3~ - 21 -
g3~
01 cell (Box 92), so that No output of Box 100 must be
02 followed.
03 Bvx 102 When the No output of Box 100 is
04 followed, as indicated in Box 102, Tab Pointer
05 Register will be set -to address the next-lower
06 address cell of the Tab Stop Register. In other
07 words, the Tab Pointer Register is decremented to
08 address the next lower possible tab setting
09 position.
Box 94 Bis Next, -the output of Box 102 (on the left
11 side thereof) is followed back up to decision Box
12 94, where again a determination is made as to
13 whether the setting in the Carrier Present Position
14 Register is equal to setting of the cell in the Tab
Stop Register currently addressed by the Tab Pointer
16 Register, which in the present round is the cell
17 with the next-to-highest address.
18 Box 96 Bis If the decision in Box 94 is No, a
19 decision is again rnade (Box 96) to see whether the
set-ting in the Carrier Present Position Register is
21 less than that in the addressed cell. If the
22 decision in Box 96 is No, the setting in the cell
23 addre~sed by the Tab Po:inter Register is now
24 established to be the closest tab position left of
the carrier, as indicated by Box 98.
26 Box 100 Bis Returning to Box 94, if the setting in
27 the Carrier Present Position Register equals the
28 setting in the cell addressed by -the Tab Pointer
29 Register, the Yes decision from Box 94 will be
followed, and a decision will be made ~Box 100) to
31 determine whether th~ Tab Pointer Register is
32 addressing the minimum address cell of the Tab Set
33 Register. If so, the Yes output of Box 100 will now
34 be followed, indicating that all possible tab set
positions have been surveyed and (Box 104) no tab to
36 ~he left of the carrier was found.
37 Box 102 Bis If the decision in Box 100 is ~o, i.e.,
3~ - 22 -
3~3
01 the tab pointer is not addressing the minimum
02 position of the Tab Se-t Register, the tab pointer is
03 again decremented (Box 102~ and the decisions in Box
04 94, 96 and possibly Box 100 are made, as before.
05 Tab Stop Found
06 Box 106 If a tab stop position to the left of
07 the carier was found (Box 98), a connection is made
08 (Box 99) to Fig. 3C where the next operation (Box
09 106) is to set a Carrier Desired Position Register
(414F) to the value in the cell addressed by Tab
11 Pointer Register 414H. This is done in order to
12 move the carrier to the setting in the cell
13 addressed by Tab Stop Register 414G.
14 Box 108 Next, a decision is made ~Box 108) to
determine whether the setting in the Carrier Desired
16 Position Register is greater than that of the left
17 margin. If so, this indicates that the Carrier
18 Desired Position is inside the lef~ margin,
19 whereupon the Yes output of Box 108 will be
followed. If the Carrier Desired Position Register
21 is not greater than the left margin, the ~o output
22 of Box 108 will be ollowed, indicating that the
23 desired tab stop is outside or. to the left of the
24 left margin. In this case it would not be desirable
to move t~e carrier further to the left.
26 Box 110 If the desired tab stop is outside the
27 left margin, i.e., the No output of Box 108 is
28 followed, next ~Box 110) the Carrier Desired
29 Position Register is set to the left margin setting
so that the carrier will go to the left margin at
31 the next move.
32 Box 112 After the Carrier Desired Position
33 Register is set to the left margin (Box 110), or if
34 the Carrier Desired Position Register's setting is
greater than the left margin (Yes from Box 108),
36 Accumulator 416 is set (Box 112) to the difference
37 between the setting of the Carrier Present Position
38 - 23 -
3~3
01 Register and that of the Carrier Desired Posi-tion
02 Register in order to indicate the number of spaces
03 by which the carrier must move to reach the desired
04 position.
05 Box 114 Thereafter, a Print Wheel Step Count
06 Register 414J (Fig. 4) is set to zero to prevent the
07 carrier Erom making a single letter space movement,
08 which it might do if a number were set in Register
09 414J.
10 Box 116 The Carrier Space Count Register is then
11 set to the "number" or "value" in Accumulator 416.
12 This .is in preparation for movement of the ~arrier,
13 which moves according to the setting in Carrier
14 Space Count Register 414C.
Next (also Box 116), the Carrier
16 Direction Flag (in Status RAM 400) is cleared. This
17 flag is normally set to move the carrier to the
18 right and the clearing thereof is in preparation for
19 a left or reverse move.
Box 118 Next, the value in Carrier Present
21 Position Register 414D is set to the value in
22 Carrier Desired Position Register 414F. This is
23 done so that the Carrier Present Position Register
24 will store the carrier's actual position after the
tab move is completed and so that the carrier will
26 return to this desired position if a machine or
27 motor error occurs during carr.ier movement.
28 Box 119 A timer (not shown) is preferably used
29 to control (among other events, if desired) a
Linefeed Motor (not shown) for rotating Platen 14.
31 In this box, the timer is reset.
32 Box 120 In this box, a decision is made next as
33 to whether the Linefeed Flag (in RAM 400) has been
34 set. If Tab Key 26 has been deeply depressed-~i.e.,
if the first reverse tab movement is being made--the
36 Linefeed and Raverse Tab Mode Flags will have been
37 set in Bo~ 88. If the Reverse Tab Mode Flag was
38 - 24 -
3L~L~3~3
01 already set ~Yes from Box 74)- i.e., a second or
02 subsequent reverse tab move is being made--then
03 Boxes 76 and B8 will be bypassed and consequently
04 the Linefeed Flag will not have been set via Box 88.
05 Box 122 If the first reverse tab movement is
06 being made, the Linefeed and Reverse Tab Flags will
07 have been set in Box 88 so that a Yes decision will
08 be made in Box 120 and (Box 122) rotation of the
0~ platen one line ahead, in accordance with ~he
invention, is started. Substantially a~ the same
11 time, the carrier will stArt its move (Box 124) in
12 the left direction by -the value in the Carrier Space
13 Count Register--iOe., to the next left tab stop.
14 If a second or subsequent reverse tab
movement is being made, the Reverse Tab Flag will
16 have been set so that a Yes decision in Box 74 will
17 cause ~ox 88 to be bypassed and the Lineeed Flag,
18 which is cleared at the end of the Eirst rever~e tab
19 movement (see Box 126 below) will still be clear, so
that a ~o decision will be made in Box 1200
21 Accordingly~ Box 122 is bypas~ed and only the
22 carrier move (Box 124) to the next tab stop position
23 at left is performed. The reverse move is then
24 completed.
While a relatively large number ~f
26 decisions and operations have been described as
27 occurring between the Forward Tab Move (Box 77) and
28 the Reverse Tab Move (Box 122), in actualityl due to
29 the high clock rate of the machine, the Reverse Tab
Move appears to occur substantially immediately
31 after the Forward Tab Move.
32 Box 126 After completing the above rnoves, then,
33 as shown in this box and in accordance with the
34 invention, the Linefeed Flag, which was originally
set in Box 88 upon entry into the Reverse Tab Mode,
36 is cleared in order that subsequent shallow
37 depressions of the tab key will eEfect a reverse tab
38 - 25 -
~3~3
01 move without a linefeed, as discussed supra.
02 Box 44 Bis As seen Erom Box 126 the sequence
03 returns to Box 44, the Next Key Routine, which
04 includes Box 54 where the oldest Key Code in F'IF0
05 Register 414A is transferred to New Key Register
06 414I, via the Accumulator. IE the tab Key has been
07 depressed twice in succession, the Key transferred
08 will be the tab key but, if not, the key will be a
09 character, space or other key. Discussion of these
circumstances will be undertaken subsequently.
11 Tab Stop ~ot Found
12 Box 128 Returning to Box 104 (Fig. 3B3, if no
13 tab to the left of the carriex was found, a
14 connection is made (Box 105) to Fig. 3C where a
decision is then made ~Box 128) as to whe-ther the
16 carrier is presently at the left margin, i.e., is
17 the setting in the Carrier Present Position Register
18 414D equal to the setting in the Left Margin
19 Register 414E? If so, the carrier cannot be moved
to any tab stop position and the machine proceeds
21 (Box 130) to the user error subroutine in which
22 error lights (not shown) are flashed.
23 Box 132 If the carrier present position is not
24 equal to the left margin position, the No decision
output oE Box 128 will be followed and the Carrier
26 Desired Position Register will be set (Box 132) to
27 the value in the Left Margin Position Register in
2~ order to move the carrier to the left margin.
29 Thereafter, the actual carrier movement is completed
as indicated in Boxes 112 to 126.
31 Box 44 Bis Whether or not a tab stop -to the left of
32 the carrier is found, the Reverse Tab Movement
33 procedure ends at Box 126, as seen above. From
34 there the output is again followed back to Box 44 of
Fig. 3A, at which point the machine resumes its
36 normal idling or Next KQY Routine.
37 Fig. 3A---Tab Key Held Deep Depressed
38 - 26 -
01 If the typis~ holds the Tab Key deeply
02 depressed during and after -the reverse tab move, the
03 machine will not make any further reverse tab moves
04 after the first one because of the sequence which is
0S now followed in Fig. 3A.
06 Boxes 46 and 52 .The Key Waiting Flag is not set
_.
07 since it was cleared upon delivery of the waiting
08 Tab Key Code from ROM 402 to the FIFO, as explained
09 supra, and the typist has not depressed a key other
than Tab Key 26. (Such action would be an error, as
11 it would override the desired reverse tab
12 operation.) Thus the No output of Box 46 is
13 followed. The FIFO-Empty Flag is set, so the Yes
14 output of Box 52 i5 also followed.
Boxes 78 and 80 The Repeat Terminal Flag is set
16 since it is assumed that the Tab Key is being held
17 deep-depressed. In Flag was set in Box ~7 and was
18 never cleared so the Yes output of Box 80 is also
19 followed.
BOX 133 The Repeat Flag is tested in Box 133.
__
21 Since that flag was cleared in the reverse tab entry
22 (BOX 90), the No output of Box 132 is followed, back
23 to the idling routine (BGX 44). ThUs no further
24 reverse tab moves will occur, even if Key 26 is held
25 deep depressed.
26 _ g 3A~-Tab Key Released
27 _ox 134 When the tab key is released, the
28 machine will follow the No output of Box 46, the Yes
29 output of Box 52, the No output of Box 78 (the
Repeat Terminal is no longer made active since
31 Switch 408 will now be open~ to Box 134 where the
32 Yes output is followed since the Repeat-In Flag,
33 which was sei in Box 87, was never cleared. Th~
34 routine will proceed through Box 82, follow the Yes
output of Box 84 (the FIFO is empty) and the No
36 output of Box 86 ~a flag check operation identical
37 to that in Box 7i3) to Box 136.
- 27 -
33
01 _ox 136 In this box, the Repeat and Repeat-In
02 Flags are cleared and the machine returns to its
03 idling routine.
04 _g 3A--Tab Ke~ Pressed Again
05 After the irst reverse tab move, which
06 was accompanied by a linefeed, if the Tab Key 26 is
07 pressed again but ~his time only shallowly, the
08 machine will pursue the following rou-te through the
09 flow chart to effect a second reverse tab movement
(path 38 of Fig. 2C): Ye~ ~rom Box 46, Box 48, Box
11 50, No from Box 52, Box 54, Yes from Box 56, Box 58
12 to Box 60 in Fig. 3B, Yes Erom Box 62, No Erom Box
13 66, Box 72, Yes from Box 74 (the Reverse Tab Mode
14 Flag, set in Box 88, was never cleared), through
Boxes 90, to 98 and 106, 120, as described above.
16 In Box 120, as stated, the ~o output will be
17 followed since the Linefeed Flag was cleared in Box
18 126 on the first reverse tab movement, the result
19 being that Carrier 18 will be moved (Box 124), but
not Platen 14, in accordance with the invention.
21 Fig. 3A--Non-Tab Key Pressed
22 The Reverse Tab Mode can be exited by
23 depressing a character key or almost any function
24 key other than Tab. When this is done, the machine
will proceed along the "First Pass" route o~ Fig. 3A
26 to Box 56, the non-tab key being detected and the No
27 output then followed to Box 138, where the Reverse
28 Tab Mode Flag is cleared, thereby exiting the
29 Reverse Tab Mode. The path then proceeds -to Box 58
for up-date of the F~FO pointers before passing
31 onward to Key Decode (connector Box 60) w~ere the
32 non-Tab Key is identified and processed in normal
33 fashion, -the details not being relevant here.
34 FIG. 4 - BLOCK DIAGRAM OF HARDWARE
-
A block diagram oE the electronic system
36 of Control Circuit 28 to effect the operations in
37 the flow chart of Fig. 3A and 3B is shown in Fig.
38 - 28 -
.r~.
~ , '
0l 4. In practice, all the components in the control
02 circui-t may be formed within a single integrated
03 circuit or microprocessor chip~ Appropriate
04 ampliEication of output signals for driving the
05 printed and other mechanisms will also be provided.
06 In order to facilitate understanding, simplify the
07 explanation, and avoid undue length, only the
08 typewriter components relating to the inven-tion and
09 their ancillary components are detailed. Also only
the most important inputs and outputs, data
11 interconnections, and address interconnections o
12 the invention components are shown in the block
13 diagram of Fig. 4. Omitted are details of the other
1~ typewriter components and various ancillary circuits
and lines to and from the components of the
16 invention s.ince their implementation is either shown
17 in the above-referenced applica~ions or is readily
18 practicable by those skilled in the microprocessor
19 or logic circuit design arts, given -the flow chart
of Figs. 3A and 3B together with the block diagram
21 of Fig. 4.
22 As indicated by t:he legend at right of
23 Fig. 4, address busses (which generally carry
24 information designating an "address" or location in
a memory matrix) are desi~nal:ed by double lines
26 inter-connected by zig-zag llnes, and data busses
27 (which generally carry substantive information) are
28 indicated by double lines interconnected by parallel
29 slant lines. The num~ers in parentheses adjacen-t
various busses--e.g., "(7)"---indicate the number o
31 lines or conductors in the bus. As is well known in
32 the art, a seven-conductor bus can transmit data
33 words or by-tes oE seven bits, and since each bit
34 represents a digit in radix 2--i.e., the presence
(O~E bit) or absence (ZERO bit) of successive powers
36 of two in a summed progression from 2 to 26--such
37 a bus can transmit decimal numbers (radix 10~ up to
3~ - 29 -
~3~q33
01 127.
02 A Keyboard Interface Unit 401 receives
03 inputs directly from ~Ceyboard 12, these include
04 inputs designating se1ected characters, index
05 (linefeed), a backspace input, a correct input, a
06 tab set (Key 22), a tab clear ~Key 24), a tab
07 activate (Key 26), margin controls, space, and
08 return, as indicated.
09 Preferably Keyboard 12 employs an
10 acoustic sanding means and Interface 401 includes
11 ROM 402 (mentioned earlier) and appropriate
12 circui.try which converts the resultant acoustic
13 inputs into appropriate data signals in a parallel
14 readout format suitable -for directly driving Print
Wheel 16 and other m~chanical outputs, as detailed
16 in the above-mentioned applications. A control
17 signal indicating the availability of these data
18 signals i8 sent directly to RAM 400 vi.a line 403 (as
19 ~tated earlier). A standard keyboard employing
electrical switches throughout can be used instead;
21 in this case Keyboard Inter~ace Unit 401 would be a
22 more common variety.
23 Status RAM 400, already mentioned, is a
24 register having sixty-four single-bit storage cells;
it stores various flags indicating the sta-tus of an
26 ongoing operation or any instruction for the machine
27 to follow upon its usual interrogation rounds. RAM
28 400 is periodically polled or interrogated as part
29 of the normal idling routine of the system in order
to determine if any flags are set, and if set (or
31 not set), the system will execute an appropriate
32 subroutine. E.g., when Repeat Switch 408 is closed,
33 an appropriate stage of RAM 400 will become set
34 thereby to indicate that the machine should repeat
an operation or enter a special subroutine, such as
36 reverse tab. RAM 400 is polled via an address input
37 from an address bus 418 which selects a desired
38 - 30 -
01 stage in RAM 400. RAM 400 thereupon supplies a
02 single output indicating the s-tatus of the stage
03 selected.
04 RAM 400 receives eleven control tnputs.
05 Four come directly from keys or switches on ~n
06 adjacent Keyboard 12, one (pitch selection) comes
07 from a printed circuit board (not shown), one comes
08 from the print wheel to indicate a home position,
09 four come from motors (directly and indirectly) as
feedback signals, and one (left end) comes from a
11 limit switch on the machine's frame. The inputs are
12 labelled and not all of these will be detailed since
13 they are well-known to those skilled in the art.
14 As stated with regard to the Repea-t
Terminal input on lead 409 which is of most
16 interest, when Tab Key 26 is deeply depressed, the
17 voltage on l~ad 409 to ~AM 400 will become active.
18 In practice, the voltage on that lead is positive
19 when inactive and falls to a ground level when
active, i.e., when Repeat Switch 408 is closed.
21 This is indicated in Fig. 4 by connection of lead
22 409 to positive voltage source 410 via resistor
23 412. The same circuit is associated with Tab Clear
24 Key 24; it also operates Switc-h 408 by a bail, which
can be the same bail as Bail 404. When Tab Clear
26 Key 24 i5 shallow-depressed (Switch 408 still open),
27 any tab setting at the carrier's present position
28 will be cleared, and when Tab Clear Key 24 is
29 deep-depressed, all tab se-ttings will be cleared
regardless of the carrier's position.
31 Reerring to the upper lefthand corner
32 of Fig. 4, a Dead Key and Hammer Energy Latch and
33 ROM 420 has 256 stages of three bits each. It
34 receives information from a data bus 422,
specifically it receives processed key infor~ation
36 from a FIFO (first-in-Eirst-out) register 414A and
37 latches (stores) this key information. The stored
38 - 31 -
~3'~33
01 key information i6 read when needed to determine if
02 the key is a "dead key" (i.e,, the carrier does no-t
03 advance after printiny t~e key's character, such as
04 a letter which is to have an accent mark typed over
05 it) and also to determine which of four possible
06 hammar energies to use when printing the
07 character--e.g., less energy would be used to print
08 a character with a small area, such as a period
09 ("."), than a character with a large area, such as a
"W".
11 Arithmetic Logic Unit (ALU) 424 receives
12 information from data bus 422 and Accumulator 416,
13 already mentioned. It performs simple arithmetic
14 and logical (comparison) opera-tions, such as the AND
and OR functions, addition, subtraction, division,
16 etc. when these operations are required by the
17 system. For example, using ALU 424, the existing
18 number of spaces from the le:Ethancl margin a~ which
19 Carrier 18 is presently positioned can be added with
a nurnber representing an incremental movement of
21 Carrier 18 in order to provicle a sum equal to the
22 new position of Carrier 18. ALU 424 also makes
23 appropriate computations to control the carrier
24 return position and computati.ons to calculate the
shortest possible path and corresponding direction
26 of rotation when Print Wheel 16 is to be rotated
27 from one character to another character. ALU 424
28 supplies a data output to Accumulator 416 and a
29 control output to an Instruction Disable Unit (IDU)
426. The control output to IDU 426 can be either a
31 carry, greater than, or "equal" ou-tput to indicate
32 the result of a comparison in ALU 424.
33 ~ccumulator 416 is a temporary storage
34 register which, e.g., holds information being worked
on by ALU 424, in well-lcnown fashion. As indicated,
36 Accumulator 416 receives and supplies information to
37 data bus 422 and ALU 424.
38 - 32 -
~ ~ 3~6~
01 Instruction D.isable Uni-t (ID~) 426
02 receives inputs from ALU 424 and Status RAM 400 and,
03 according to the input received, can supply a "skip"
04 inpu-t -to an Instruction Decoder 428 which causes a
05 Program Counter 430 to increment one extra count.
06 I.E., when ALV 424 supplies a comparison ("carry,"
07 "greater than" or "equal") output, or when Status
08 RAM 400 supplies an output--indicating a set (true)
09 or non-set (false) flag--IDU 426 can supply a skip
1~ signal to Decoder 428 in accoxdance with the state
11 of the particular output which will in turn cause
12 the next sequential instruc-tion to be skipped. Thus
13 IDU 128 can effect a skip or not as to the result of
14 a comparison or a flag test.
Data S~orage RAM 414, already mentioned,
16 has registers which hold variable data, i.e., it has
17 a FIFO (first-in-first-out) Register (A) for storing
18 characters corresponding to keys actuated but not
19 yet printed, a Correction Register (B) for storing
the last group (ten in one embodiment) of keys
21 actually typed, a Carrier Space Count Register (C~,
22 a Carrier Present Position Register (D), Left and
23 Right Margin Registers (E), a. Carrier Desired
24 Position Register (F), a Tab S-top Register (G)
which, as mentioned, has sixt.een four-bit cells for
26 storing tab stop settings, a Tab Pointer Register
27 (H), a ~ew Key Register (I), a Print Wheel 5tep
28 Count Register (J), FIFO Pointers tKl, K2) and other
29 registers not relevant to the present invention.
RAM 414 can be considered as having sixty-four
31 locations, each capable of holding seven bits of
32 informa~ion. Some of Registers 414A to 414K
33 correspond to respective locations, while others,
34 such as Correction Register (~) and Tab Stop
Register tG), require several locations. In
36 well-known fashion, the information in any selecte~
37 register in RAM 414 can be read out by providing an
38 33 ~
01 appropriate address input on an Address Bus 418 and
02 applying an appropriate and well-known con-trol or
03 read input (not shown) from Decoder 428 to enable
04 the data to be read into or out o~ RAM 414 via Data
05 Bus 422 leading from its right side.
06 Address Latch 432 receivcs an address
07 from a current instruction being e~ecuted and holds
08 it so that such address can be supplied -to RAM 414
09 (via a Decoder 434) for enough time for data to be
read out or written at the appropriate point in RAM
11 414, in well-known fashion. Latch 432 supplies the
12 six bits of the address to Decoder 434.
13 Decoder 434 operates to select or enable
14 one address in RAM 414 or RAM 400 (one o-f sixty-Eour
stages) at which to write in or read out
16 information.
17 Storage Register 436 is used for
18 subroutines; it stores the information word ~rom
19 Program Counter 430 to which to return after the
subroutine is completed. Re~lster 436 has three
21 stages of eleven bit.s each.
22 Program Counter 430 causes the system to
23 operate in accordance with the instructions on the
24 flow chart by supplying appropriate address to a
Program ROM 438. Program Counter 430 tends to
26 supply sequential addresses, but works in
27 association with Storage Register 436 such that when
28 the machine is ready to call any subroutine, the
29 current address or count in Program Counter 430 will
be stored in Register 436. After the subroutine is
31 completed, the stored address in Register 436 will
32 be returned to Counter 430 so that it can cause the
33 machine to resume its regular routine of operation.
34 Also, as stated in the discussion of IDU
(Instruction Disable Unit~ 426, an address in
36 Counter 430 can be skipped if IDU 426 causes
37 Instruction Decoder 428 to increment Program Counter
38 - 34 -
3~3~
01 430 a second time. Counter 430 also can be set to
02 any address by an unconditional branch instruction:
03 this will cause eleven address bits in an
04 Instruc~ion Latch 440 to be passed around on Address
05 Bus 442 through Storage Register 436 and then -to
06 Counter 430, where they will be latched.
07 Program ROM 438 contai~s the actual
08 program of -the system, i.e., in response to
09 sequential or other address inputs from Counter 430,
it delivers appropriate instruction words (each
11 having an address or data and operation code) which
12 cause the machine to operate in accordance with the
13 flow chart of Fig. 3. For example, Program ROM 438
14 selects appropriate stages of Status RAM 400 in
order to determine whether cer-tain flags are set at
16 appropriate times. Program ROM 438 contains an
17 Input Decoder and Drivers and Output Drivers, as
18 indicated. ROM 438 has 1536 stages of thirteen bits
19 each.
Instruction La~ch 440 holds the
21 instruction word of Program ROM 438 curren-tly being
22 executed, in well-known Eashion.
23 Instruction Decoder 428 receives -the
24 output of Latch 440. Decoder 428 is a ROM which
controls the actual physical operation of the
26 machine by gating information in and out of various
27 units of the machine via the bus lines, under
28 control of Program ROM 438. ~s stated previously,
29 Decoder 428 can also cause an instruction to be
skipped in response to the skip signal from IDU
31 426. The output or control lines of Decoder 428 are
32 merely indicated by arrows in Fig. 4 because their
33 connections are well-known and including them would
34 make the figure less easy to follow.
Bufer 444 is a tri-state device, i,e.,
36 it can supply a bi.nary ONE output, a binary ZERO
37 output, or provide a high input-to-output
38 - 3S -
'',~" '
01 impedance. It connects address bus 442 on its left
02 side to -the outputs oE the machine and also connects
03 data into R~M 414 via data bus 422.
04 Clock and Power On Reset Generator 446
05 provides the master clock pulses for the machine and
06 also resets all the registers oE the machine (power
07 on reset) when the machine is ~irst turned on. For
08 purposes of simplification and ease of illustration,
09 the various outputs of Generator 446, which lead to
most of the blocks in the figure, are not shown, but
11 the connections are well-known to those skilled in
12 the art.
13 Also not shown is a timer uni-t for
14 providing various time delays, when required by
operation of the machine. Further, a power supply
16 and biasing network for energizing the various
17 circuits is not shown either.
18 Miscellaneous Output Register and
19 Drivers 448 provides outputs to drive various
~unctions of the mac'nine, suc~ as a print hammer, a
21 warning tone to indicate the set margin is being
22 approached, a linefeed to ro-t:ate Pla~en 14, a print
23 or correct ribbon lift control, detents for Print
24 Wheel 16 and Carrier 18 which hold these elements in
a fixed po~ition when not in use, and various
26 indicator lights as noted.
27 Carrie~ Decoder and Driver Register 450
28 drives the motor which controls the horizontal
29 position o Carrier 18, by interpreting the
instruction bits supplied on Data Bus 422 from ROM
31 438 to select appropriate windings for causing the
32 carrier to move either to the right or to the left,
33 in increments. When a tab move is called, data will
34 be supplied to Register 450 so as to cause the
carrier motor (not shown) to move to the next tab
36 stop at either left or right, in accordance with the
37 depth oE depression of Tab Key 26.
38 ~ 36 -
~3~"33
01 Print Wheel Decoder and Driver Register
02 452 controls the motor which rotates Printing
03 Element 16, thereby to select appropriate characters
04 to be typed. When a character is called, data will
05 be supplied to Register 452 so as -to cause the prin-t
06 wheel motor to ro-tate wheel 16 to the selected
07 character.
08 FIGS. 3 & 4 - OPERATION
09 The system o Fig. 4 implements the flow
chart operations of Figs. 3A and 3B in -the following
11 manner:
12 When Tab Key 26 on Keyboard 12 is
13 depressed deeply, the tab input is coded--as by an
14 acoustic signal to the previously-mentioned
circuitry (not shown) to generate the Tab Key code
16 in ROM 402--and, due to actuation of Switch 408 by
17 common bail 404, the Repeat Terminal lead 403 to
lB Status RAM 400 goes active (to ground)~ When the
19 code is available, a signal is sent on line 403, and
immediately sets the Keyboard Waiting Flay of Status
21 RAM 400. Likewise, the active state of Repeat
22 Terminal lead 409 immediately sets the Repeat
23 ~erminal Flag in Status RAM 400, as stated
24 previously.
As part of its routine interrogation
26 rounds, thP machine wi~l then test selected flag~ in
27 RAM 400--e.g., the Key Wai-ting Flag, and since thi~
28 was set by a key actuation on Keyboard 12, the
29 corresponding code from ROM 402 will be entered into
FIFO Register 414A. The Xey codes in FIFO Register
31 414A will be processed--in order of their entry into
32 FIFO 414A--by trans-Eerring t'ne key codes Erom
33 Register 414A to New Key Register 414I and then to
34 Accumulator 416. When the tab key code is
transerrPd in its turn to New Key Register 414I and
36 Accumulator 416, that code will be identi-Eied as a
37 function code and the value in Accumulator 416 then
38 - 37 -
~ 5~3
01 compared for equality with a series of function key
02 codes obtained from Program ROM 438 in a
03 pre~selected sequence. When the value :in
04 Accumulator 416 is eventually compared with the tab
05 code (binary code for decimal 115), equality will
06 exist (Yes output oE Box 62), and ALU 424 will
07 provide a "true" signal on its "equal" output line
08 tFig. 4) ko IDU 426. As a result, in accordance
09 wi-th previous description, instead of causing a
skip, the output of IDU 426 will cause Instruction
11 Decoder 428 to advance Program Counter 430 to
12 addres~ the next sequential instruction in ROM 438,
13 which is an unconditional branch. The machine will
14 thus jump to the tab subroutine, as explained in
more detail below and as derined in the subsequent
16 blocks of Fig. 3B.
17 Note that the above-mentioned tests o
18 the value in Accumulator 416 (tab code~ against
19 other function codes ~ave rise to "false" signals on
the "equal" output line of AI.U 424 and, under
21 control of IDU 426 and Decoder 428, these generated
22 skip inputs to Program Counter 430 which caused each
23 associated unconditional branch to be bypassed in
24 the fashion previously described and known in the
art.
26 More particularly, the above-mentioned
27 no-skip causes a "branch-to-tab" instruction. This
28 is accomplished by transf rring that instruction
29 which is at the next sequential address in Program
ROM 438 to Instruction Latch 440. This will, in
31 turn, cause the coumt in Program Counter 430 to be
32 abruptly changed ("jumped"~ to the par~icular
33 address for the start of the tab subroutine (Box
34 6~). This is done by passing the eleven least
signiicant bits in Latch 440 twhich latched the
36 unconditional branch instruction, including the
37 particular address indicated by these bits) through
38 - 38 -
01 Storage Register 43~, and into Program Counter 430.
02 Counter 430 now addresses the initial portion of the
03 tab program stored in Program ROM 438--i.e., that
04 portion associated with Box 66. Execution oE thls
05 portion of the program proceeds as follows:
06 The first decision to be made (Box 663
07 is to determine whether the left margin setting (in
OJ3 a Left and Right Margin Register 414E) is greater
09 than the setting in the Carrier Present Position
Register 414D. This test is accomplished by a count
11 comparison in ALU 42A. If, as is usual, the left
12 margin reading is not greater than the carrier
13 present position, ALU 424 will provide a "false"
14 input to IDU 426, which will then supply a skip
input to Decoder 428~ Program Counter 430 then will
16 be caused to increment by one extra count so -that it
17 addresses the next sequential instruction in ProcJram
18 ROM 43S (the instruction ater the unconditional
19 branch). In response to -the new instruc-t.ion, the
six least significant bits in Latch 440 are put on-to
21 Data Bus 422 via Buffer 444 and these bits are hei!d
22 in Aadress Latch 432. This group of bits or address
23 in Latch 432 is then decoded by Decoder 428 which
24 selects one of the locations in Status RAM 400. As
indica~ed in Box 72, the addr.ess selected is that o-f
26 the Margin Release Flag and that stage is thereupon
27 set in known fashion to permit direct tabbing to any
28 tab stops at righ~ of the right margin.
29,-~ Before continuing with the normal
routine, note that if the left margin setting is
31 greater than the carrier present position, ALU 416
32 will detect a "greater than" and send a "true" input
33 to IDU 426, which last will not cause a skip inpu~
34 to be sent to Decoder 428. Accordingly, -the very
next instruction of the sequence, an unconditional
36 branch, will be executed. As a result, Program
37 Counter 430 will be set--via Storage Register 436,
38 - 39 -
13L~93r9~3
01 as explained previously--to the address in Latch 440
02 corresponding to the start of -the program section
03 associated with Box 68. Execution of this portion
04 of the program then proceeds, i.e., the Carrier
05 Desired Postion Register will be set to the value
06 stored in the left ma.rgin .register, and a forward
07 move oE the carrier t.o the leEt margin executed ~Box
08 70) in steps not rele,vant here.
09 ~len (Box 74~, a check is made to see iE
the Reverse rrab Mode Flag is set. The address of
11 this Elag in R~M 400 as selected by ~he six least
12 significant bits of t.he instruction in Latch 440,
13 which are transferredl-to Latch 432 via Bu:Efer 444
14 and Data Box 422 and decoded by Decoder 428, in the
fashion described pre!viously with respect to the
16 Margin Release Flag (Box 72)~ If the flag is set,
17 the output of Status R~M 400 will be true, and an
18 appropriate input wil.l be sent IDU 426 which will in
19 turn not provide a sk:ip input to Instruction Decoder
428 so that the next instruction will not be
21 skipped, but will be addressed and fetched in
22 sequence by Program C'ounter 430O This will be an
23 unconditional branch instruction, which will cause
24 Program Counter 430 t:o be set to the address of the
2S start of the program section associated with Box 90
26 (the next operation, since the Yes output of Box 74
27 bypassed Boxas 76 ancl 88). For this purpose, the
28 eleven leas-t ~igni~ic!ant bits in Instruction Latch
29 440 (which latched the unconditional branch
instruction) are agai.n passed through Storage
31 Register 436 and loacled into Program Counter 430.
32 The Program Counter now addresses the start of the
33 reverse subroutine (i.n ROM 438) and execution of
34 this por-tion of the program accordingly proceeds.
If, on the other hand, the output of
36 Status ~ 400 is fa].se--i.e., the Reverse Tab Mode
37 Flag is not set~--IDU 426 will provide a skip input
- 40 -
~ ~3~t~ ~
01 to Instruction Decoder 428 which will cause (as
02 above) ~rogram Counter 430 to increment by one extra
03 count. The Program Counter then addresses the
04 instruction in Program ~OM 438 sequentially
05 followi~g the next or unconditional branch
06 instruction. The unconditional brarlch instruc-tion
07 has, thereore, been skipped. E~ecution of the
08 skip on alse flag instruction is completed at
09 this point.
The Repe,~t Flag is then checked (Box 76)
11 in the same fashion as the Reverse Tab Mode Flag was
12 checked (Box 74). I:E the Repeat Flag is clear, as
13 it will bs initially because of the sequence of -the
14 signals obtained upon deep depression of Tab Key 26,
a forward tab move operation is ini-tiated (Box 77 ),
16 but if the Repeat Flag has been set, the operations
17 in Box 88 will proceed, under the aforedescribed
18 steps in wh.ich a skip input :is not generated and ~he
19 very next instructiom in the tab program sequence is
followed, giving rise to a jump in the setting oE
21 Program Counter 430.
22 ~he program proceeds as indicated with
23 operations in rectangular boxes being carried on
24 according to straight-forward sequential program
commands (generally, and excepting jumps for
26 returning to the main program path) and decisions in
27 diamond boxes being 3electively implemented by
28 presence or absence of a skip input from IDU 428
29 under control of the output of ALU 424 or an input
from Status ~AM 400.
31 Moving down to Boxes 120, 122 and 124,
32 these depict the first reverse actions as a resul-t
33 o the reverse tab subroutine, which actions depend
34 on the state of the :Linefeed flag. As seen in Box
120, if the flag is set (true, or yes ), the
36 response is a let move routine including a linefeed
37 (Box 122) because the platen is to index one line.
38
~t33~93
01 This response does not require branching because
02 only a single step is required: an appropriate
03 command is sent to Miscellaneous Output Register and
04 Drivers ~48 which activates, for example, the
05 line~feed drive motor (not shown~. Activation is for
06 a fixed time (the timer having been reset in Box
07 119, as previously mentioned~ to operate properly a
08 cam mechanism (also not shown) such as the one
09 disclosed in the ~.S. Patent 4,365,90~ issued
December 18, 1982, invented by Hans W. Mueller et
11 al, enti-tled "Linespacing Apparatus".
12 Since activation of the linefeed drive
13 motor is for a fixed time, completion of linefeed is
14 not required before proceeding, so with
substantially negligible delay, the next sequential
16 instruction is fetched and it (together with others
17 following it) causes the carrier to be moved in the
18 left direction by the desired amount (Box 124 in
19 accordance with Box 116). Appropriate instructions
are provided to Carrier Decoder and Driver Register
21 450 from Bu~fer 444 under control of Instruction
22 Decoder ROM 428. If the opexation of Box 122 is
23 bypassed (by virtue of a skip input of the type
24 described previously), the same carrier move is
effected, but without the lime~eed, because the same
26 point in the program is reached in either case.
27 After the action in Box 126 (described
28 above) the reverse tab move will be complete!. Note
29 particularly that the! clearance (Box 126~ is
effected in essentially the same sequence as the
31 setting of the Margin, Release Flag (Box 72) except
32 that a zero is writte!n in the cell of Status RAM 400
33 corresponding to the Linefeed Flag.
34 Although a complicated and relatively
lengthy sequence of operations was described, due to
36 the high clock rate of operation of the electronic
37 system, these moves t:ake place very rapidly when Tab
38 - ~2 -
01 Key 26 ls depressed or is deep-depressed.
02 While the above description contains
03 many specifities, ~hese should not be considered as
04 limited the scope of the invention since many
05 ramifications of the embodiment descxibed will be
06 apparent to those skilled in the art. For example,
07 in the reverse tab operation described, a first deep
08 depresslon of the reverse tab key causes a reverse
09 tab motlon plus a linefeed or index, and subsequent
shallow depression oi- the reverse tab key causes a
11 reverse tab operation only. This mode of operation
12 can be lmplemen~ed mechanically in a non-electronic
13 typewriter by providing a linefeed upon a first
14 reverse tab operatiorl and by providing an
approprlate mechanism to prevent linefeed upon
16 subsequent reverse tab operation~. The
17 "anti-llnefeed-upon-c;ubsequent-reverse-tabs"
18 mechanism would be c]eared upon opera-tion of any
19 character or space key. Also while the -tab and
reverse tab operations were operated by a slngle Tab
21 Key 26, it will be apparent that a separate reverse
22 tab key can be provicled, in which case the reverse
23 tab key would have only two positions, i.e., off and
24 on; in the on po~ition the tab activate input to ROM
402 and the actuation of Repeat Switch 408 of Fig. 5
26 would occur. Many variation~; in ~he rules for
27 entering reverse tab, especially in association with
28 the margins, can be made within the scope o the
29 invention. Also, in lieu of making a forward tab
move first, the machine can alternatively go
31 directly into the reverse -tab movement upon
32 activation of the reverse tab function, say by
33 introduction o sufficient delay to permit sensing
34 subsequent closure ol. Switch 408 during tab key
depression, although this is not preferred because
36 of possibly noticeable delay accompanying -the more
37 frequently used forward tab moves. Accordingly it
38 - 43 -
3~'~3
01 is therefore desired that the true scope of the
02 inv~ntion be determined only according to the
03 appended claims and their legal equivalents.
04
05
06
07
08
09
11
12
13
14
1~
17
18
19
21
22
23
24
26
27
28
29
31
32
33
34
3~
37
38 - ~4 -
