Note: Descriptions are shown in the official language in which they were submitted.
11 7~ 8
This invention relates to a serial transmission
system particularly useful with electronic postage meters
~f the type having a keyboard for the entry of postage
to be printed, a display for displaying postage to be
printed as well as other data, an electronic accounting
device, and a printing mechanism.
Devices of this type are generally known, and are
discussed, for example, in U.S. Patent No. 3,978,457.
This patent discloses a system for a postal meter including
a Xeyboard for the manual introduction of data corresponding
to the postage to be printed.
This application is a divisionai application of
Canadian application Serial No. 363,541, filed October 29.
1980.
In prior devices of the general category including
electronlc postal meter operation, lt has been found
deslrable to employ one or more microprocessors to control
varlous meter functions and operatlons. For security
reasons, all data relating to accounting may be maintained
separately from other data relating to nonsscure information.
By séparate maintenance of secure data it is therefore
possible to improve security while employing concepts of
distributed processing by the use of multip~e processors.
The use of multipls processlng in a secure
environment places stringent requirements on error rate in
interprocessor communications, which requirements must bs
satisfied in order to have successful operation. It is
further desired to provide a system of this type which can
easily subrogate its control authority to an external unit,
thereby allowing substantial]y one hundred percent control
of meter function to be transferred to an external device,
without any change in system hardware. In additicn,
the use of electronics in postal meters allows the
mg/~ - 2 -
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capability of greater sophistication in automatic recharging
the accounting registers without the need for operating
personnel It is a desirable feature of any meter therefora
to provide improved methods of detecting tampering and
performing self-diagnostic error checking.
It is a feature of the present invention to provide
an interprocessor communication system which will minimize
error as a result of multiple processor inter-communication.
The foregoing objects are achieved in accordance
with the present invention by the provision of a serial
transmission system comprising first and second terminals
each having a transmitter coupled to a send line and a
receiver coupled to a receive line, the transmitter line
of each terminal being coupled to the receive line of the
other terminal, each terminal comprising means applying a
given signal level to its respective send line, each
terminal comprising means responsive to the given signal
level at its respective receive line for enabling the
respective transmitter to change the level of its send line
and then transmit messages asynchronously on the respective
send line, the terminals being responsive to levels other
than the given level at their respective receive lines for
inhibiting transmission.
In a preferred embodiment of the invention, the
postal meter is provided with three units, which although
mechanically connected together, are each provided with a
CP~, and are each provided with a crystal controlled clock.
In accordance with the invention, the frequencies of the
clocks of the different units need not be identical, and
the communication between the units is by way of serial
messages that are asynchronously transmitted and received.
The format of the messages, and the timing of the bits in
mg/j - 3 -
~1731~8
different units is precisely set, however, to insure that
messages may be sent and received without the necessity for
synchronizing the different units. In addition, upon
receipt of the first bits of a message from a transmitting
unit, the received bits are retransmitted by the receiver
back to the transmitter for comparison, to enable the
transmitter to send a no error within a minimum period of
time following the complete message transmission, verifying
the correctness of the message as sent and received.
All control and data signals utilize the same
pair of conductors in each direction with precisely defined
timing for control.
For providing external control, the control flow
is in one direction and information flow in the other
direction.
All control of the meter and all information inside
the meter can be controlled by connection through an
interface connector. All functions performed by the meter
are controllable electrically from a remote location,
except purely local manual functions such as power on and
date change. This results from the communication capability
of the data units. The organization of the three units
results from a flow of commands or control of data from
the control unit to the accounting unit and then to the
printer unit, for example, relating to a new value of postage
and where it is to be set. The flow of information is in the
opposite direction, such as, for example, a current register
value or the like. Within this concept, connection of an
external device, such as an electronic scale, to the control
- 30 unit can operate to place commands or data control instructions
information into the meter.
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~ "
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~ he interface operation allows the external device
to take control of the meter, disabling the keyboard.
The external device can communicate messages with the
display, thereby eliminating the need for a keyboard and
display in the external device. One specific advantage
of the foregoing arrangement is that the control unit may
be physically replaced by the attached external operating
device, without any changes in the accounting unit or the
printing unit, either in hardware or software.
In order that the invention will be more clearly
understood, it will now be disclosed in greater detail
with reference to the accompanying drawings, wherein:
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1~731~8
Fig. 1 is a simplified perspective view of a postal
meter which may incorporate the system of the present invention;
Fig. 2 is an enlarged view of the panel of the postal
meter of Fig. l;
Fig. 3 is a simplified block diagram of the orientation
of the elements in accordance with a preferred embodiment of
the invention;
Fig. 4 is a simplified diagram of the circuitry of
a control unit for a postal meter in accardance with the
invention;
Fig. 5 is a simplified diagram of a circuit for the
accounting system of a postal meter in accordance with the
invention;
Fig. 6 is a more detailed block diagram of a
preferred embodiment of the control unit for a postal meter
in accordance with the invention;
Fig. 7 is a circuit diagram of an opto-electric
isolator that may be employed in thé present invention;
. Fig. 8 is a more detailed block diagram of a
preferred embodiment of an accounting unit in accordance wi~.h
the invention; and
. Fig. 9 is a block diagram of a preferred embodiment
of the electrical system of the printing unit of a postal
meter in accordance with the invention.
1~731~8
Fig. 10 is a timing diagram illustratlng the
re-co~unication operation of the invention~
Fig. 11 is a logic diagram illustrating trans-
mission from the meter~
5Fig. 12 is a logic dlagram illustrating trans-
mission to the meter~
Fig. 13 is a diagram illustrating multiple
external devices daisy chained to the meter~
Fig. 14 is a sequential set of flowcharts
10illustrating the control unit operation~
Fig. lS is a sequential set of flowcharts
illustrating the printing unit operation.
Fig. 16 is a sequential set of flowchar~s
illustrating the accounting unit operation.
11731~8
.
~ eferring now to the drawings, and more in particular
to Fig. 1, therein is illustrated a postage meter 20 removably
affixed to a base 21, in accordance with one embodiment of the
invention. In this arrangement, a slot 22 is provided between
the postage meter 20 and the base 21 at the forward edge thereof,
for receiving envelopes or the like and the printing of postage
thereon. The postage meter is provided with a display panel 23,
preferably an electronic display device, as well as a control
panel 24 which may be organized in a manner to be disclosed in
the following paragraphs. The apparatus may be energized by way
of a supply cable 25.
The postage meter 20 illustrated in Fig. 1 may be of
the type that is removable from the base 21, and the base 21
may be of the type disclosed, for example, in U.S. Patent
No. 2,934,009, Bach et al., incorporating a mechanical drive
for operation of the printing mechanism in the meter 20. The
séparability o the meter and base renders the electronic meter
compatible wlth conventional driving units, simplifies servicing
of the device and, if necessary, simplifies transport of the
meter for recharglng i remote charging capabilities are not
employed.
The panel for the postage meter is more clearly illus-
trated in Fig. 2, wherein it is seen that the meter is provided
with a numeric display 30, for example, a conventional
multiplexed seven-segment LED or LCD display. In addition, the
keyboard is provided with numeric setting keys 31 and a decimal
key 32 operative therewith, for setting the meter to print a
desired amount of postage, the amount normally being displayed
on the display 30. A clear key 33 may also be provided to
clear the display amount in the event, for example, of an
e~roneous entry. When the displayed amount has been set to
--8--
117;~1~8
the desired value, depression of a set postage key 34 effects
setting of the print wheels for setting postage.
The panel may further be provided with a series of
keys enabling the selective display of other values on the
display 30. For example, depression of a key 35 may enable the
display of the contents of an ascending register, i,e., the
amount of postage issued by the meter, and depression of a
key 36 may enable display of the contents of a descending
register in the meter, i.e., the amount of postage for which
the meter is still charged. Further keys 37-40 may enable
display in a conventional manner of other specific specialized
values such as the control or postage sum, piece count,
batch value, and batch count, respectively. The batch
value and batch count registers can be cleared by simultaneous
depression of either batch value key or batch count key and
the clear key C. The panel additionally preferably is provided
with an LED 41 which will be lit upon each application of
power to the meter, as is conventionally done at the beginning
of a day, to indicate that the dater has not been set or that
the dater door is open. A further LED display 42 may be
provided and interconnected to be lit if necessary to reset
the trip mechanism in the base before operatior. is to continue.
In order to provide recharging of the meter, for
example, by way of the keyboard, the meter may be provided
with a key slot 45 illustrated in Fig. 1, in which the key 46
of Fig. 2 may be inserted. The shaft of the lock may be
visible through a window 47 to display the position of the key.
Thus, in the normal setting of the key this shaft may display
the message operate as illustrated. This arrangement may
also be employed for remote meter resetting, as discussed,
for example, in U.S. Patent No. 4,097,923.
As a further feature, the meter may be provided with
a service switch 50 at the rear thereof for the convenience of
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13~731;~8
field service personnel enabling use of the keys of the meter
for different functions. Upon operation of the switch 50,
the keys 35 through 40 may thereby enable the display of
; additional values such as the unlock value, the low postage
warning amount, the meter nùmber, diagnostic status, and the
maximum settable amount. Turning the switch to an -enter
combination-- position, as indicated in the window 47, while
entering a correct coded combination in the keyboard, enables
the recha.ging mode of the meter to be effective. In the
charging mode, which may be attained by means of an internal
switch lock controlled by the key 46, an -enter amount--
position as shown by this message at the window 47, may enable
entry of postage funds in the recharging value registers of
the meter by way of the keyboard. Returning the key to the
operate position enables the resumption of the use of the
meter for printing postage.
The service switch may be in an unsecured position in
the meter, since the display of the additional values rendered
possible by the use of this switch doés not affect the security
of the meter, and merely enables the display of further values.
The fact that it is these values that are being displayed may
be shown by distinctive underlining of the display, if desired,
and the operation of the service switch 50 partially disables
the set postage key 34. It will then not be possible to set a
new value of postage in the postage meter when it is in the
-service-- mode and the interposer will act to block operation
of the meter in the service mode. However, the set key may
still be used to cause the display of the currently set value.
When the meter is in the service mode, i.e., with the
switch 50 operated, and the switch 45 and key 46 are activated,
the entry into the keyboard of a new value and a code indicating
the function of that value, will enable the resetting of the
A mg/ ~ 10 -
~ 73168
unlock value, low warning postage amount or maximum settable
amount, respectively. The "unlock" value is a determined
value, for example, one dollar, including and above which the
operator should be careful in setting so as to avoid accidental
printing of excessive amounts. For this purpose, all values
including and above the unlock value require an additional step
on the part of the operator, such as an additional depression
of the set postage key 34. The display may be provided with a
distinctive indication, or example, one hori~ontal bar, to
indicate that the printing wheels have been set but the unlock
step, i.e;, the additional depression of the set postage key,
has not been effected. The completion of the unlock step would
be indicated by the display, for example, of three horizontal
bars to indicate that the meter is enabled to be tripped, to
print postage.
If the descending register does not contain sufficient
fund~ to cover the set amount on the print wheels, the entire
display may be caused to blink. On the other hand, if ~he
value stored in the descending register is lower than the low
~0 postage warning limit, the decimal point may be caused .o blink~
The ~maximum settable" amount, of course, cannot be ~xceeded in
the:setting o~ any postage.
The meter may also be provided with a "privi1eged~
swltch 51 that is normally held in the operate position by a
seal. The operation of this switch, following the cutting of
the seal, enables the recharging of the meter by post office
personnel in a nonremote charging mode.
In addition, the meter is provided with one or more
arithmetic function keys 52, enabling a variation of the
~O postage setting amount, such as the addition of further values
to the already displayed setting value prior to the depression
of the set switch 34. This feature enables the introduction
~173~8
~y the operator of f~rther values, such as insurance or the
like, without the necessity for manual calculation or
calculation on a separate device.
The internal components of the postage meter in
accordance with the invention are preferably oriented as
illustrated in Fig. 3, and include a first compartment 55
that is physically secure, i.e., as secure as is reasonably
possible to avoid tampering with internal components thereof.
While it may not be possible to provide 100% security in this
o regard, physical evidence of tampering will be evident in any
event before entry can be gained. The compartment 55 encloses
the printing module 56, which may include a mechanical printing
assembly, and if desired, a separate microcomputer
for controlling this module.
L5 The compartment SS also encloses a further compartment
57, which is preferably electromagnetically shielded, and
encloses an accounting module 58. The accounting module is
connected to external devices, i.e., external of the compartment
57, only by optical or similar isolation couplers 59 as disclose~
in appllcant~8 Canadian Patent No. 1,077,17Y, issued May 1, 1980,
in order to avoid damage theretor either accidental or intentional
resulting from introduction of noise, for example, excess voltages
into the accounting module. Such coupling is, of course, not
provided for the energy source thereof, which extends to a power
supply 60 in a separate compartment 61 also within the secure
compartment 55. The power supply 60 is energized by way of a
filter 62 within the compartment 61, to insure the absence of
any voltage variations that would adversely affect the account-ns
module, the power input to the compartment 61 being directed
into the compartment 5S from a power supply system in a further
compartment 63 that is preferably defined by the outer secure
housing of the compartment 55. Thus, while it is not absolu~ely
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. .. .
necessary for all the elements within the compartment 63 to
be physically secure, this feat~re is preferred.
The power from the mains plug 64 is fea into the
compartment 63, from where it may be fed by way of a suitable
connection 65 to power the meter base. The power for the metes
may be fused in the compartment 63, by means of a fuse 66,
applied from the fuse to a thermostat 67 and thence to a
transient suppressor and filter 68. The thermostat inhibits
application of voltage to the unit in the event of excess
temperatures. Further protection for the system is provided
by means of an isolation transormer 69 and an overvoltage
cut-out device 70. The power or the meter is finally applied
to an energy storage device 71, such as a large-valued capacitor
71, the capacitor 71 having adequate energy storage to enable
the self-protection eatures of the meter to operate, such as
to transfer data to a nonvolatile memory, in the event of a
power failure. The reduction of voltage may be sensed by a
sensor 72 in the secure housing 55, with one output of the
sensor being directed to the accounting module for signaling
the necessity of a mode change, and another output (which can
be mechanical) for inhibiting further printing module functions.
A further output of the isolation transformer 69 may
be ed externally of the meter to a control unit 75, and one of
the isolated outputs of the accounting module may be directed
through the chamber 63 also to the control unit. The control
unit 75 may thus constitute a keyboard control unit such as
illustrated in Fig. 2, including the key switches, displays,
etc., necessary for local operation of the device. It is thus
apparent that the system of Fig. 3 orients the elements of the
postal meter so that elements which are less critical to the
security of the postal meter system are provided with successively
lower levels of physical ana electrical security.
~,~,,
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1~ 731~8
A preferred embodiment of a control unit 75 is
illustrated in Fig. 4. This unit, for versatility in
design, as well as for minimizing the noncritical elements
that must be isolated in the physically secure housing,
preferably incorporates a central processing unit 80,
for example, of the 6500 series, and connected by way of
conventional data lines, control lines and address lines
to a multipurpose conventional R~l/ROM I/O timer circuit 81
incorporating read-only memories, random access memories,
timing control elements and input/output interface hardware.
By the use of suitable decoders 82, the keyboard 83 ~ay
thereby be scanned in the conventional fashion, and by the
use of suitable drivers 84 the visual display 85 may be
energized, preferably in a multiplexing mode according to
conventional practice. The data relating to the depression
of any of the keys of the panel may thereby be communicated
to the processing unit 80, for the development of a serial
input/output on the lines 86 for communication with the
accounting module 58 within the secure housing 55. The
processor 80 and circuit 81 are responsive to the
requirement for operator intervention to recock the trigger
mechanism in the base, and the failure to open or close
the dater door 28 (Fig. l) following application oE power
to the unit, to energize selectively an indicator LED 87
corresponding to the indicators 42 and 41, respectively,
of Fig. 2. The service switch 50 may also be connected to
the circuit 81. If further input/output devices are
coupled to the control unit, such as external display
devices or control systems, these may be coupled to the
unit by way of further input/output lines 88, preferably
serial communication paths which may be suitably isolated
by opto~electric isolators. The unit may comprise an
internal power supply and regulator 89 connected to receive
power from the postage meter low voltage power as shown in
Fig. 3.
The above-discussed functions under the control of the
control unit are thus functions which are not critical in the
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1~73168
" , ~
sense that loss of control or the contents of any register
therein will not result in loss to the post office department,
or to the user, of funds. These functions have been relegated
to the control unit in order that the secure portions of the
postal meter include only that peogramming of the system which
must be secure. Additional functions that may be effected by
the control unit, such as the addition of sequentially entered
amounts, may also be controlled by the program of the aontrol
unit, since such calculations are not critical to the security
of the apparatus, and need not be effected within the physically
secure portions of the postal meter. Similarly, the service
resettable functions may be effected by the programming in the
control unit, since these functions also are not critical to
the accounting system and eegisters themselves. However, to
retain these parameters in nonvolatile memory, retention in the
accounting unit is desirable.
It will, of course~ be apparent that, in a system such
as shown in Fig. 4, further arithmetic keys may be provided,
without great difficulty, such that the postage meter may be
alternately employed also as a calculator.
Alternatively, the central processing unit and its
control circuit may be augmented by a calculator chip or the
like, connected to the keyboard and display for performing
arithmetic functions.
While the control unlt of Fig. 4, including all of
the functions of the panel shown in Fig. 2 is preferably
disposed directly on the postage meter to form a part thereof,
it will be apparent that this portion of this system may be
physically separate therefrom, or separable therefrom, whereby
the postage meter itself may incorporate only the elements that
are required to be physically secure.
f~ ' '
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1~73168
Since monetary information and control is prevalent
in the serial communication employed in the system, a high
degree of integrity is mandatory. For this purpose, the system
is designed, in the serial transmission communication sections,
such that a transmitted bit is returned or "echoed" by~the
receiver thereof for c~ecking purposes. If the transmitter
th~reby~eeceives all of the echoed signals satisfactorily, it
may,issue\a "no error" pulse, thereby informing the receiver of
the information that the received information is valid.
The~ircuit arrangement of the accounting co~partment
is shown in somewhat ~reater detail in Fig. S, ~herein the
walls 90 of the compartment are illustrated as preferably
forming an electromagnetic shield. The circuits include an
accounting microcomputer 91 having a nonvolatile memory control
92 coupled thereto. The nonvolatile memory control ccntrols the
application of stored data between a volatile memory, which may
form a part of the accounting microcomputer 91 and a nonvolatile
memory 93. The volatile memories, such as random access memories~
may function as working ascending registers, working descendin~
registers, ana the like. The accounting microcomputer also
includes read-only memory control for the necessary accounting
routines, as well as control routines. This unit may, in
addition, incorporate serial interfaces, to enable its interfacin~
with the printing and control modules. The microco~puter may,
for example, comprise the 8048 series microc4mputer from Intel
Corporation, Santa Clara, California, with a control circuit in
a manner similar to that described above with respect to the
control unit 75. In order to avoid damage to the accounting
module by electric surges applied accidentally or intentionally,
and to eliminate e.ectrical noise induced via groundloops, the
accounting microcomputer communicates with the devlces ext~rn~l
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.
of the compartment 57 by suitable isolators that are not
capable of applying voltage surges to the microcomputer. These
isolators may, for exampie, be in the form of opto-electronic
couplers, and are also preferably arranged so as to be inaccessible
from the exterior of the postal meter. One isolator unit 94 may be
pcovided for the two-way communication path with the control unit.
A further isolator arrangement 95 may be provided for the two-way
communication wltb the printer unit, i.e., the printing module 56
of Fig. 3, in particular, the microprocessor circuit thereof. A
still further isolator 96 may be provided for applying the power
sen~ing signal5 to the mi¢rocomputer 9l. In addition, an
isolator 97 may be provided foc controlling an lnterposer ~not
shown~ in the prlnting module, for example, or mechanically
blocking functions of the prlnter. Such a system i8 disclosed,
for example, ln appllcant'~ patent appllcation Serial No.
346,655, flled February 2~, 1980.
The nonvolatile memory 93, at the present state of the art,
is preferably in the form of an MNOS memory, which does not
require a back-up power source. This memory may, however,
alternatively be formed o elements which do require a power
back-up, in which case a power control circuit may be employed
to apply back-up power thereto external from the compartment 57.
The purpose o the power control circuit 9B is to provide power
to the MNOS memory for the purpose of effecting its data transfer
operation, essentially during power up and power down. The
program of the microcomputinq unit 9l is organized to enter the
contents of the registers of the computer units into the non-
volatile memory as soon as any indlcation of failure of the power
supply occurs, and to restore this data to the working registers
upon restoration of the power.
11731~
The thermostat 67 in Fig. 3 cuts off power to the meter
in the event of high or low temperature operation. This
automatically places the meter in its power down cycle, as a
result of the power cut-off.
The compartment 57 may further comprise a temperature
sensor 99, with suitable circuits (not shown) coupled thereto,
such as to the microcomputer, for transferring data to the
nonvolatile memory in the event of excess temperatures. The
system may further be operative to prevent the operation of the
interposer solenoid by way of the isolator 97, in the event of
excess temperatures. It will be appreciated that the interposer
is controlled by the microcomputer 91 also to inhibit operation
of the printer in the event that insufficient postage remains
for a printin~ operation, or other accounting data indicates
that the unit should not be operative.
While the isolators have been indicated as individual
units, it is, of course, apparent that these units may incorporate
multiple devices, so that two-way communication is established
in the respective circuits. It is further noted that systems
for the transfer of data between volatile and nonvolatile
memories are well known, and are di6closed, for example, in
applicant's Canadl~n Patent No. 1,119,730, issued March 9, 1982.
Referring now to Fig. 6, therein is illustrated in
greater detail a block diagram of a preferred embodiment of a
control unit in accordance with the invention. In this figure
the blocks have been identified by part numbers and terminals
where applicable. This unit is illustrated as incorporating a
type 6503 CPU 100 having its data and address lines coupled to
RAM/ROM 1/0 timer circuit 101 as well as to a type 2716 PROM 102,
the PROM 102 having stored therein the program for the control
unit. Control lines, such as the interrupt line and read/write
line may also be connected to the circuit 101. The circuit 101
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1173168
has a plurality of ports, as will be discussed.
The control unit further incorporates the keyboard 103
including the numeric keys 31, the display keys 35-40, and the
three-position switch 45 shown in Fig. l. This unit also includes
the add-through key 52 and the set postage key 34. All of these
keys ana switches are connected in a matrix to the circuit lOl,in
a conventional manner, to permit the scanning of the keys and
switches in accordance with the program, to detect a key or
switch closure. The eight-line port A, as well as four lines of
port B of the circuit lOl, are also connected to the seven-segment
display panel 104 for multiplexed display in the conventional
manner. The circuit 101 is further connected by a pair of serial
ports for communication to and from the accounting unit. In
addition, a pair of further serial ports enable communication to
and from external devices, by way of opto-electric isolators 107
and 108, respectively. Another output port of the adaptor is
connected to LED lO9 for indicating on the display panel that the
dater door has not been closed. A further output port is con-
nected to an LED 110 on the display panel for indicating that the
operator's intervention is required to recock the trigger mechanism
on the base. Finally, another port is coupled to the service
switch 50, to enable the functions of the postal meter in the
service mode.
In the preferred embodiment of the invention, the,program
of the control unit is directed to servicing of the keyboard unit,
display panel, etc., so that the control functions and storage of
data are effected primarily in the accounting unit. The program
thereby includes those functions necessary for the scanning of the
keyboard, multiple~ing of the display, ormatting of signals for
communication with the othe~ units, and with external devices,
etc., so that any new information may be passed on to the
accounting unit.
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1~"73168
A typical opto-electric isolator is shown in Fig 7,
this constituting primarily a conventional 6N136 device 115
including a solid state emitter for producing optical signals
for reception by a photodiode~ t~e photodiode being connected
in the base circuit of a transistor amplifier.
A block diagram of a preferred example of the accounting
unit is illustrated in Fig. 8, wherein a type 8039 CPU 120 is
shown to communicate with the control unit by way of opto-electric
isolators 121 and 122, and to communicate serially with the
printer unit by way of opto-electric isolators 123 and 124. The
opto-electric isolators 121 and 122 within the accounting unit
thus may pe( connected directly to the corresponding leads of the
control unit. The isolators 123 and 12i may be connected directly
to the printer unit signal channels, since no further isolation
devices are necessary for this purpose. In addition, a control
opto-electric isolator 125, for controlling an interposer or the
like in the printing unit~may be connected to a further port of
the CPU 120. Signals corresponding to a pending power faîlure
are further fed to the interrupt port of the CPU 120, by way of
opto-electric isolator 126. It is thus apparent that~ata and
control signals to and from the accounting unit must be dlrected by
way of opto-electric isolators, in order to insure the electrical
and physical integrity of this unit. The accounting unit further
includes a plurality of PROMs 127 coupled to the address and data
lines o~ the CPU 120, each PROM 127,for example, being a E-PROM
type 8755. This unit is connected to an electrically alterable
read-only memory ~EAROM3 128~ for example, a type ER 3400, serving
as a nonvolatile memory to store data at times during which the
power supply to the postage meter has failed, or has been inten-
tionally disconnected. ~he working memory for the accounting
system, including the registers for storing all operational data,
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are provided in the CPU 120, this data being transferred to
the electrically alterable ROM 128 at such time that a reduction
Of power is sensed. In order to insure the complete transfer of
data, storage capacitors may be connected m a conventional manner
to store adequate power to insure the proper functioning of the
circuit until the transfer of data has been effected.
A preferred example of the circuit of the printing unit
is illustrated in Fig. 9, this circuit consisting primarily of
the CPU 130, for example, a type 8748-8, the CPU being connected
by way of suitable buffers where necessary, to the I/O devices
within the printing unit itself. The me-chanical and opto-
electric sensing systems in the printing unit are conventionaland may be generally of the type disclosed, for exa~ple, in U.S.
Patent No. 4,050,374 and aforementioned copending application
Serial No. 346,655. Thus, the CPU i8 connected to a
plurality of opto-electric senBor~ (not shown) for sensing
of the positioning of the prlnt wheels, these lines also being
connected to enable the sen~ing of the privileged access switch
51 of Pig. 2, The privileged access switch 51 is located within
the printing unit and i8 accessible only by way of a door sealed
by the post office. These lines of the CPU are further connected
to sense the position of the dater door, the dater door switch
and privileged access switch being strobed by way of a further
output of the CPU 130. The LEDs for the optical sensors are
2s strobed at the proper times by way of another output of the CPU
130, and still further outputs of the CPU enable the stepping
of the bank and digit stepping motors for ~he print wheels. In
addition, the CPU 130 has a pair of ports for serially communi-
cating to and from the accounting unit. Further, the interposer
output from the accounting unit and another output of the CPU
130 control a pair of transistors 131 for energizing the interposer
-21-
. . . 1173168
solenold, whereby the interposer solenoid 153 is not energized
until all the precondltionY are met both in the accounting
unit and the printing unit. As a result, a printing cycle
cannot commence unless the physical and electrical conditions
in the meter are correct for normal printin~. In the printing
unit, it is theref~re ev~dent that the program is provide~
within the CPU itself.
Postal meters o~ the above-described form may be provided
with several modificatlon~. For example, ln one modific2tion
a remote charging featureis ava-~labl~
whereby the key is provided for operation of the three-position
charging switch on the keyboard. The operator of the unit may
thus be provided with asuitable combination for entry into the
kçyboard, to enable remote charginq li.e., away from the post
ofice)~ In such unlts the privileged access switch is omitted.
In a further modiication, the three-position recharging
switch on the keypoard may be controlled by ~ 3imple knob, without
the necessity o~ a key. In thls type of a system,
the meter may be manually ~echarged at the post offlce, but the
service functicn~ may be efected locally in a manner similar to
~hat of remote ~echarging system type units.
In other words, recharging of a postal meter of the above
type can be effected locally, 1~ devices are provided with a key
for the three-position switah, in wh~ch event further security
25 i6 re~uired a~ will be discussed later. On the other hand, in
postal meter6 having a simple knob switch lnstead of the key
switch, the "privlleged access~, sealed at the post office, ls
provlded for manual recha~glng.
In the normal mode of operation of the 6ystem, as above
discussed, the s~x display keys, when depressed, efect the
display on the display panel of the ~lx parameters above noted,
-22-
ll'Y31~B
i.e.,~the total in the ascending register of all postage that
has been printed, the total remaining in the descending register
of postage available, the control sum, the total number of
printing operations of the meter, the value of postage printed
and the number of pieces that have been printed since the last
batch clear operation of the associated registers. The depression
of these keys results only in the number of concern being displayed
for a timed period after the key is released, for example, two
seconds following which the display will return to the postage
setting
In either type of meter, if the service switch is placed
in the service position, with the three-position switch still in
the operate position, the display function of the display keys
will be different. Thus, depression of the "postage used" key
1~ 35 will now result in a display of the current value set in the
dollar unlock register in the machine, at or above which an
operator cannot print postage. Postage values above this value
require an additional depression of the set postage key for
operation, in order to avoid accidental printing of excessive
postage values. Depre~sion of the "postage unused" key 36 will
now result in a display of the value in the low postage warning
register at which a warning should ~e given that the contents of
the descending register are below a determined amount. Depression
of the control or'postage sum" key 37 will now result in the
display of the serial number of the postal meter. Depression of
the "piece count" key 38 will now result in a display of the
diagnostic status of the meter. This display provides an
indication to the serviceman of possible malfunctions . A
depression of the "batch value" key 39 will now result in a
display of the maximum settable amount, i.e., the maximum amount
set internally within the meter, above which the meter cannot
set the print registers. Depression of the "batch count" key
40 w111 h~ve no effect in the service mode.
11731`68
The three-position switch is used to effect
recharging of the meter or to effect the change of values
in the registers concerned with dollar unlock value, the
low postage warning amount and the maximum settable amount.
With the remote recharging feature, positioning
the three-position switch in either the enter combination
or enter amount-- positions enables the customer to enter
a combination or amount respectively into the meter via the
keyboard with indication on the display. When the three-
position switch is controlled to leave this position, the
display value is entered into the accounting unit and the
display is blanked for the next entry. Return of the
three-position switch to the operate position will cause
the accounting unit to complete the recharging routine and
return the meter to normal usage with the recharging amount
added to the postage unused register. The combination for
the remote recharging feature is obtained from a remote
data center and is a random or pseudorandom number which
changes with each recharging for security reasons.
For meters with the manual recharging feature,
the recharging mode is effected by breaking the seal of
the privileged access door, and flipping of the privileged
access switch. The same sequence of operations of the
three-position switch described above for recharging the
meter are followed as in those meters having the remote
charging feature. In the manual recharging system machine
only post office personnel are permitted to effect the
change. The combination is a fixed number known only to
the post office and is stored within the meter. Normal
operation of the meter may proceed once the privileged
access switch has been returned to its operate position.
m~ 24 -
~731~8
To change values in the registers concerned with
the dollar unlock value, the low postage warning amount and
the maximum settable amount, the serviceman would place
the meter in the service mode by placing the service switch
in the service position. The three-position switch is used
as described above for the entry of combination and amount
values. The meter will interpret the combination value to
indicate which register is to be changed.
For the remote recharging system meter and the
manual recharging system meter, if an error has been made
in entry, the occurrence of this error will be deemed to
constitute evidence of tampering with the machine. When a
determined number of such errors have been made, for example,
nine, since the last setting of the meter, then the function
of the machine in recharging postage will be inhibited.
The return of the meter to operating status in such circumstances
may be effected at the post office. A discussion of the means
to return the meter to full operating status is not of
consequence to the present invention and relates to the
security of the meter.
As above discussed, each of the three units of the
postal meter has a microprocessor with a read-only memory
defining a given program, and the communication between the
unlts is effected serially and asynchronously. This is
achieved in the first place by providing each of the computer
systems with a crystal-controlled clock. Further, the
signals are defined such that the transitions thereof are
closely controlled, whereby it is insured that, if a signal
is present, it must be present within a given time period.
As a still further insurance of the correctness of communication,
the bits of a signal are returned to a transmitter as soon as
they are received, for error chec~ing at the transmitter, whereby
mg/ ~ - 25 -
li~31~i8
a "no error" bit may be transmitted ilNmediately following a
data message i~ the data has followed correctly.
The program of the control unit responds to the status
~f the postal meter with respect to determined parameters.
S A register in the microprocessor of the accounting unit
holds meter status information, for example, of two bytes,
the bits of which digitally indicate if the meter trip mechanism
requires recocking, if the dater door has not been opened
following the last application of power or i9 presently open,
if there are insufficient funds to allow printing of the amount
set in the print wheels, if the low postage value has been
reachea, if the meter is in a service mode, if the meter is
enabled, if the batch registers are clear, if a trip has been
completed, or if variou$ types of errors have occurred. The
lS status message associated with these bit8 is not the same as the
diagnostic message noted above that is employed in the service
m~de. The accounting unit ~eeps the control unit informed of
the current status by transmitting a fitatus message to the control
unit after power has ~een turned on and, thereafter, whenever a
change in status occurs. The control unit responds to all such
me~sages by insuring that the display on the meter is consistent
with the status message a~ above discussed. These later steps
may include, for example, the display of a row of decimals in
the event of certain errors, the flashing of the decimal point
in the event of low postage funds, the flashing of the entire
diRplay in the event of in~ufficient postage, and the displaying
of underscores in the place of blanks if the meter is in the
service mode.
An interrupt program in the control unit interrupts the
main program of the control unit at regular intervals in order
-26-
~, . .
~17316~3
to scan the key~oard and keyswitch, and to drive the display.
In ord~r to prevent the display of spurious characters which
can be produced by snea~ currents when more than one key i8
pressed, the interrupt program will cause the display to go
s blank instead. Such values as relate to time, keyboard, and
keyswitch are maintained by the interrupt program for use by
the main controller program.
The main program for the control unit includes the
initializing steps, program steps for the transfer of messages
back and forth between the accounting unit and external devices,
control of the timed display, the checking of the status
message to insure that dater door and reset base lights are
lit in accordance with the status, responding to the reported
positions of keys, and the three-position switch to ascertain
lS change~ of state therein so that the control unit subroutine
which corresponds to the function defined for such a state or
change o ~tate will be executed.
The program of the accounting unit includes initiali~ation
procedures to insure that the working registers are brought up
to date, and that no postage has been printed that has not
been accounted for, a~ well as a power down proces~ing program
to efect the transfer of data to the nonvolatile (electrically
alterable) memory in the event that the power is shut down or
is failing.
The main program of the accounting unit effects the
transmission o the meter status message to the control unit
upon request or change in status, determines the effect of
any currently entered postage value on the funding data
currently registered and makes any necessary varlations in the
status message. The main program also controls the timing
in the accounting unit for Feceiving messages from the control
unit and the printer. The accounting unit program further
117316~3
includes subroutines for processing o~ signals in the bringing
of the registers up to date when postage is to be printed, and
for controlling the operation of the system when the meter
is tripped. A further subroutine controls the bringing of
the meter status message up to ~ate. In addition an error
checking routine which involves cyclical redundancy checklng
is programmed in the accounting unit software. ~rhis will be
described in further detail below.
The program of the printer unit includes a main program
having initializing steps, steps for scanning the sensors and
controlling the strobes for the LEDs of the sensors, and the
processing of messages for communication with the accounting
system. Subroutines are provided for the setting of the
postage wheels, to determine if sensor readings are proper,
and ~o determine if any changes have been made in the outputs
of the various hardware sensors and switches such as the
privileged access and the dater door switch.
-28-
~173~8
Wlth respect to the p~ogx~m for setting the display
unlock value, maximum ~ettable amount and low postage
amount, as discussed above, the keys effectlve for such
setting in the above-described manner are matrixed ln
5 the keyboard and ~canned periodically to determlne lf a
change in the status has been effected. The scanning
positio~ also occur~ with respect to the servlce switch,
in the control unit, whereby the control of any of the
keys and switche~ is communlcated to the accounting
unit for storage therein and proces~ing. For example, if
the service ~witch is set t~ lts ON po~ltion, then the
scanning, which is also effective with respe~t to the three-
position switch, enables as a display routine,to enter
comblnation routine or enter amount routine, in dependence
lS upon the position of the three-position switch.
In the display sub-routine, the data in a register
corresponding to a depressed display ~ey is sent to the
control unit for display. In the enter combination sub-
routine, the next entry into the ~eyboard i8 stored, so
that the value entered into the keyboard when the three-
position switch has been turned to the enter amount position
will be entered into the corresponding register in the CPU
of the ~ccounting un~t, whereby the thus entered value
will be effective in future operatlon of the machine in
normal operating procedures. It is~ of course, apparent
that the testing of the set values during normal operation
i5 effectively made with respect to a value range, for
example, a range of postage values less than or greater
than the ~tored amount, so that the necessary indlcation
-29-
.
A
- 1:173168
can be given. The term "indication" as employed in
this sense refers to the display. When the entexed
postaye value exceeds the maximum setta~le amount, the
entered value is ignored, and the display returns to its
original postal value. The service settable features as
above disclosed may also be considered to effect the
control of the postal meter to different states, such as
a non-operatiVe state~ when the maximum settable value
has been exceeded, a low value warning state when the low
value ind~cation is flashing, and a dollar unlock value
state reguiring an additlonal depression of the set key
when the amount set in the display exceeds this stored
value.
-30-
3~
With further respect to system diagnostics, b~iefly
referred to above, two ~sic error checks are provided in
the software routine of the meter. These two checks are
termed fatal and proc~dural, respectively. Under the
'i category of fatal error checks, two sub-categories are
defined. These two sub-categories are termed hard and soft,
respectively. Hard errors are determined by monitoring hard-
wa~e sensors, such as the bank and digit select sensors,
interposer position sensors, shutter bar sensor, and the like.
A failure of these sensors to provide proper readings will
be termed a fat~l ha~d error; will lock up the meter and will
be non-recoverable upon power-up. Central authority inter-
vention will be required to permit further operation of the
meter.
~5 Another exa~ple of a fatal harderror is a resulting
non-compare from a c~clic redundancy check. Each data
register is continually monitored. Using standard poly-
nomial techniques, a cyclical redundancy remainder is
calculated for each updated data register value. When a
power-down cycle is initiated;the contents of each data
register and its associated cyclical redundancy remainder
is transfexred to non-volatile memory. Upon power-up, the
cyclical redundancy remainder of each data regi6ter is
again calculated and compared to the cyclical remainder
previously calculated upon power-down. A non-compare will
produce a fatal hard error.
Fatal soft errors relate to the intercommunication
capability of the meter units. Thus, communication errors
between internal units such as the accounting, printer and
-31-
` 11731`~8
control units will be sensed, based upon the bit retransmission
previously described. In additon, communication time-out
functions are provided, so that the failure of a unit to
communicate within a specified period will also produce a
soft fatal error. Soft fatal errors will block meter operation.
Unblocking can be effected by recycling the meter; that is to
say, the meter is turned off, then on again, thereby causing
recycling and clearing the error. The power recycling will be
counted in a data register and, as noted above, upon reaching
a predetermined number, could cause total lock up if desired.
In other words, a predetermined number of soft fatal errors
equals a single hard fatal error.
Procedural errors,such as improper
(high) value entries, or an attempted improper procedure,
manifest themselves as visual flags on the display.
Other diagnostic checks, as well as variations as set
forth above, may be easily accommodated within the software
routines implemented herein.
By allowing data to be communicated between units on
a message basis, serially, and by employing the "echo"
technique previously described, the implementation of the fore-
going error checking capability is achieved expeditiously.
jrc~ 32 -
1173168
As above discussed, the inter-unit communication is
serial channel, bit synchronous, character asynchronous,
start/stop communication, for example at 9600 baud. The
communication is solely on the basis of messages, i.e.,
separate control lines are not provided between the units
for control of the communications. This type of communication
is also provided for with respect to communications between
the control units and external devices. The messages are 10
bits long, each including a start bit followed by an 8-bit
word, or byte, and terminating with a stop bit. The last stop
bit of a message has a sense opposite to that of all other
stop bits of the message, in order to indicate the end of
the message. A logical zero is indicative of a start bit,
an end of message bit, and a data zero or low. A logical
one is provided for a request to send, a clear to send, an
end of byte, a data one level, and also serves as a no-error
pulse. The first word of any message has a coded two-bit
field stating whether the message contains information, data
or control functions. Another bit of the first word indicates
whether or not the message concerns the display only, or if
it only concerns the accounting unit. The remainder of the
bits of the first word are specific message identification
bits.
mg/y,~ - 33 -
" ~ ,
1:1731~8
.
If the messages have more then one word, the second
word of the message may contain a format byte, ~onsisting
of two nibble5/ i.e., four-bit groups. The fir9t nibble tells
the number of nibbles of data in the message, and the second
nibble gives th~ number of digits to the right of the decimal
point of the data, or corresponds to a hexadecimal F if there
is no decimal point.
When a message is ready to be sent by a unit, the
receive line of the unit i5 first tested. If it is low then
the transmitting device raises its send line to a high, and
again tests the receive line. If it is still low, the unit
is free to transmit, otherwise, it must become a receiver.
This avoids contention between two units. With respect to
units of the postage meter itself, the programs of the
diffexent units, in the event of possible contention, give
priority to the printer unit,accounting unit, control unit
or external device in descending order. When external devices
are interconnected with the postage meter, i.e., to the control
unit, the control unit is given priority.
The timing of the messages constitutes the crux of the
communication system whereby the messages may be asynchronous.
Typical timing is thus illustrated in Fig. 10, which illustrates
the relative timing of the lines of the transmitter for sending
a given message, and of the lines of a receiver for receiving
the same message. Since the transmitter output line is the
same as the receiver input line, it will be evident that these
two signal lines are identical. The same is true, of course,
with respect to the transmitter input line and the receiver
output line.
In a successful transmission system of this type, the
~173168
transmitter tests its input line at time tl and, if a low is
detected, raises its output line to a high within 50 micro-
seconds, as shown at t2. The transmitter then again tests
its input line at time t3 within 50-100 microseconds. If
the input line is still at a low, then the transmitter can
start to send its message at time t5 following a minimum wait
of 120 microseconds, by the lowering of this output line to
form the start bit of the message. In the meantime, at
time t4 the receiver has raised its output line to a high
level in a minimum of 100 microseconds, indicating it is
ready to receive data. This indicates a '-clear to send"
condition. The timing between the succeeding bytes of a
multibyte message, as indicated by the time interval between
t5 and t5' is 1134.375 microseconds minimum, in order to
insure that the receiver has been enabled to effect proper
reception and storage o~ the signals.
The time from the beginning of the last message byte
t5' to the transmission of a no-error pulse at time t7 is
set at 1031.25 to 1157.291 microseconds, and the no-error
pulse has a width from 309.375 microsecondsto 368.228
microseconds. The receiver must test for the occurrence
of a no-error pulse at time t8 from 1187.291 to 1340.625
microseconds after the initiation of the start pulse of the
last byte of the message. The transmitter bit transitions
must be in accordance with table I, and the receiver sampling
of the data and stop bits must be in accordance with the timing
illustrated in table II.
mg/~ 35 -
.,
1173:1~8
.
r~
TABLE I
n BIT MINIMUM MAXIMUM
_
1 START 0 0
2 DATA 1 103.125 1~5.208
3 DATA 2 206.250 210.417
4 DATA 3 3~9.375 315.625
DATA 4 412.500 42~.833
6 DATA 5 515.625 526.042
7 DATA 6 618.750 6~1.250
8 DATA 7 721.875 7~6.458
9 DATA 8 8~5.~00 341.667
STOP 928.125 946.875
TABLE II
n BIT MINIMUM
1 START
2 Dl 115.2~8
3 D2 22~.416
4 D3 325.624
D4 43~.832
6 D5 536.~40
7 D6 641.248
8 D7 746.456
9 D8 851.664
1~ STOP 956.872
With the above timing, and the use of crystal control
for the clock of each of the unit* asynchronous transmission
is thereby feasible so that control leads for this purpose
between the units are ~nnecessary.
Further, in accordance with the invention, in order
to insure that the informat~on is correctly received by the
receiver without error, the data is sequentially returned to
the transmitter on the receiver output line. The times for
the retransmission of the data, from the beginning of the
instruction loop detecting start bit, are given in table III,
and the times for sampling this data on the input line to the
transmitter are given in table IV.
If, and only if,the received data at the transmitter is
the same as the sent data, will the no-error pulse be transmitted
-36-
11731~8
at the end of the message,
As a further control over the message communication,
the transmitter will wait for 3.5 milliseconds for a clear
to send signal from the receiver after presenting a request
to send transmission, and similarly, the receiver will wait
for about 3.5 milliseconds maximum for the start of a
m,essage ater presenting the clearlto send message.' Conten-
tion between units is further minimized by setting determined
periods that must be existçnt between adjacent transmitter
activity of a u~it, as well a~ between adjacent recçivers.
. ' TABLE III
. n ~ BITMINIUUM MAXIMUM*
1 START32.083 73.125
2 Dl137.292 176.25p
i5 3 D2242.500 279.375
4, D3347.708 382.500
D4452.917 485.62S
6 ' D5558.125 588.750
. ' , 7 ' 'D6663.333 691.8?5
' 8 D7768.542 795.000
; 9 D8873.750 898.125
STOP978.~58 1001.250
*Allows lp microseconds for program loop
, uncertainty in detecting start pulse. If
uncertainty is greater than lp microseconds the
. excess should be subtracted from each maximum
value.
TABLE IV
, n BIT MINIMUM MAXIMUM
1 START 103.125 135.208
2 ' Dl 206.25p 240.416
3 D2 309.375 345.625
4 D3 412.S00 450.833
. D4 515.625 556.041
'6 D5 ,618.750 661.250
7 D6 721.875 766.458
8 , ' D7 825.0~0 871.667
9 D8 928.125 976.875
. STOP 1031.250 1082.083
.
~ .
, t~
1~73168
.. . .
All control and data signals utilize the same pair
of conductors in each direction with precisely defined
timing for control.
For providing external control, the control flow is
in one direction and information flow in the other direction.
All control of the meter and all information inside
the meter can be controlled by connection through an interface
connector along lines 88, Fig. 4. ~11 functions performed by
the meter are controllable electrically from a remote location,
except purely local manual functions such as power on and date
change. This results from the communication capability of the
data units. The software routine will scan for the presence
o an external control device, and permit subrogation of
control to such external device upon recognition of its validity.
The organization of the three units ~esults in a flow of
commands or control of data from the control unit to the
accounting unit and then to the printer ~nlt. A new value
of postage, and where it is to be set, is one example of such
data and command. Thé flow of information is in the opposite
direction, such as a current register value of the like.
Within this concept, connection of an external device, such as
an electronic scale into the control unit, can operate to place
commands or data control instruction information into the meter.
The interface operation allows the external device to take
control of the meter, including the disabling o the keyboard of
the control unit, if desired. The external device interaces
with the meter on a message basis. The external device can send
messages to be displayed, or can send messages requesting the
contents of the display. The control unit programming will
permit the external device to send a message disabling
-38-
;, .
11731~
the keyboard, thereby implementing the subrogation function.
One specific advantage of the foregoing arrangement is that
the control unit may be physically replaced by an attached
external operating device, without any changes in the acccunting
unit or the printing unit, either in hardware or software.
The external device can include a plurality of operating
devices, such as a scale and a remote display. The control
unit microprocessor can be used to function as a message buffer
to allow for flexibility in the development and use of external
devices. External devices may include weighers, displays, or
other type of device normally interfacing with meters of the
type disclosed herein. The software provided in the control
unit can be implemented for this function. As shown in Fig. 11,
an external device 150 may be used to replace or supplement the
control unit function. The external device 150 is preferably
coupled through a connector 152, which may be a standard nine-
p~n connector, to the meter control unit 154, and receives
messages from the meter unit 156. The schematic illustration
o~ the meter unit 156 includes the accounting unit and the
printing unit, a~ previously described. The control unit
includes communication buffers 158 which will logically direct
communication from the meter unit 156 to the external device
150 or locally to the control unit 154. The opposite effect
is ~hown in Fig. 12, wherein external devices may communicate
with the unit through the communications buffer. The effect
i6 similar in that the buffer will receive messages from either
the external device 150 or locally from the control unit 154.
In Fig. 13 a plurality of external devices 164 are
shown, interfaced through the control unit 154 into the meter
unit. Each external unit may be provided with its own control
key for initiation of messages. Each external device could
~ 731613
include a communication buffer as part of its software
to permit operation of the external devices in a daisy
chain manner. Appropriate messages can include complete
subrogation of the control unit logic to the external device.
The control unit programming is designed to permit such
operation.
Regarding external device operation, information flows
in two directions, either inbound towards the meter or outbound
towards the external device. Control signals and requests,
defined generally as controls, flow inbound towards the meter.
Informational data flows outbound. Normally, on the inbound
leg controls originate in the control unit. However, in
accordance wi~h this feature the invention will let an external
device 150 issue commands right through the control unit to the
meter unit. Conversely, informational data on the outbound
leg, from the meter unit ~accounting) comes to the control unit
154 and is repeated on the external device line 152 to the
external device 150 if an external device is present. The
~resence of an external device 150 is determined by whether
or not it responds with a clear to send signal. If not, the
outpu~ on the line 152 goes off after a pre-set time period
~times out) and the meter continues to function normally.
This ability to pass information through the communication
buffer in the control unit allows the advantage of placing
externa~ devices thereon. The external device may be construct~d
in the same manner, with a communication buffer, as shown in the
control unit, such a device may, in turn, have an external devic~
coupled thereto. Thus, a daisy chain of external devices 164,
as shown in Fig. 13, can be provided. The only limitation on
the number of external devices which may be daisy chained in
this manner would be system tolerance and time out restriction~
-40-
1173161~
It is a further feature of the invention to provide
external devices to give certain commands to the conteol unit
itself, which commands do not necessarily need to go into the
accounting module, such as the ability to write a message to
the display of the control unit, or to read a message from
the display of the control unit, or to command the control unit
to disable its keyboard and the rotary three-position switch.
In so doing, the communication buffer responds to a bit in the
beginning of the digital transmission message sequence, or
header, and directs whether the message is to go to the meter
unit or the control unit. This bit, which has an assigned
location in the header, as described above, iæ assigned a "1"
in that position if it is a message to or from the control unit
and a lO" if it is a message to or from the meter unit. In this
manner, the control unit, when it receives a message from the
external device, can exam~ne the hoader and from this bit
determines whether the message is for the control unit or for
the accounting unit. If it is for the control unit, it stops
the message and takes the appropriate action. If it is not for
the control unit, the message is relayed to the meter unit.
~ 173168
The control unit can provide a direct reply to the external
device without involving the meter unit at all, for example,
in response to receipt of a message to read the display.
The control unit does not retain the last meter status
S message received. Thus, when a keyboard disable command is
received, for example, the control unit will request a meter
status message from the accounting unit. When the control
unit gets the response, it will insert a bit into the meter
status message to indicate whetherthe keyboard is enabled or
disabled. Once disabled the control unit will continuously
indicate a disabled state in the status message, until reset
by receipt of a keyboard enable command, or until power is
turned off and on. The keyboard will always be in the enabled
state on a~ power up condit~on.
The meter is thus capable of interfacing directly with
external devices, something that is difficult to impossible to
accomplish with present meter~.
Summarizing the above, the control unit is provided with
a connector for bi-directional communication with a variety of
2~ external devices. Thi~ enables the external devices to access
meter Lnformation, such as register readings, piece count, and
current value selection. In addition, an external device can
control the meter to the same extent that the operator could
from the keyboard~
The meter can be e~uipped with an attachment to
automatically record and charge-back postage to various departments
based on identificatio~ information entered by the operator at the
start of each mailing run. The meter can be used with a display/
receipt printer, providing the customer with a visual indication
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11731~8
of the value on the meter and/or a receipt upon payment
of postage. The meter can be used with customer-provided
devices, such as a computer terminal or minicomputer sys-
tem for real-time aata capture, as in parcel operations
S for additions of postage to an addressee's bill.
The relative ease of interfacing to the meter of
the present invention suggests further possibilities.
Two examples are: 1) use on the end of a decision-making
inserter to vary postage with varying number of inserts,
2) a~ a practical mallomat.
Flowcharts representing the sequence of operation
of the various units are shown in Figs. 14, 15, and 16.
In each case, the unlettered figure shows the manner
wherein the corresponding figure number and letter are
assembled to represent a complete flowchart.
The flowchart representing the operation,of the
control unit is shown in the sequence of Fig. 14.
The flowchart representing the operation of the
printing unit is shown in the sequence of Fig. 15~
The flowchart representing the operation of the
accounting unit is shown in the sequence of Fig. 16.
The appendix A regarding the programmed function is
attached hereto. The appendix is a detailed printout of
each of the programs contained in the accounting unit, con-
tro~ unit and printing unit~
,
-43- ,
1~7316~
It is Xnown and understood that the terms postage
meter and postal meter, as used herein, refer to the general
def$nition of a device for the imprinting of a defined unit
value for governmental or private carrier parcel, envelope
or package delivery, or other like application for unit value
printing. Thus, although the term postal meter is utilized,
it is both known and employed in the trade as a general term
for deVlCes utilized in con~unction with services other than
those exclusively employed by governmental postal services.
~0 For example, private parcel or freight services purchase and
employ postal meters as a means to provide unit value pricing
~or individual parc-ls, lncluding accounting and printing
~unctlons.
~ he pre~ent lnventlon i9 particularly directed to
uae ln a po~tal meter which will empioy varylng features and
~unction~, de8cribed in differing aspects, in any one or more
o~ the ~ollowing groups of applicant'9 copending patent
applications, including this one, all filed concurrently:
Serial-Nos. 363,503~ 363,504t 363,505; 363,506; 363,507;
2~ 363,5097 363,520 and 363,541. Applicant's U.S. Patent No.
4,266,222, i8sued May 5, 1981 is also related to these
applications.
While this invention has been disclo5ed and de~cribed with
reference to a ~ingle embodiment thereof, lt will be apparent
that variations and modifications may be made therein, and lt is
mg/~ L
1173168
intended in the following claims to cover each such variation
and modification as falls within the true spirit and scope of
the invention.
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