Note: Descriptions are shown in the official language in which they were submitted.
5~L~
' This invention relates to an el,ectronic taximeter.
More specifically, this invention relates to such a taximeter
which utilizes discrete rnicrocircuits for the purpose of forming
a dedicated microprocessor adapted to carry out the functions
required by a taximeter.
To a large extent, taximeters available in taxies
today are of the mechanical type. These are heavy and bulky and
, difficult to calibrate accurately on a time basis. In addition,
the process for calibrating mechanical taximeters to new fare
, 10 rates is awkward and expensive as it usually requires changes in
computing gears. The mechanical versions also su~fer from poor
accuracy and a lack of adequate resolution as well as limitations
on the number of optional rates. In addition, they have limited
feature capability and fail to take advantage of available
'' technology.
Electronic taximeters have also been designed, but
'~ these have failed to match the mechanical taximeters in cost and
general performance. General purpose microprocessor based
,
,1 electronic taximeters have so far proved uncompetitive due to
poor temperature performance, high cost, susceptibility to elec-
, trical interference from the cars electrical system, and general-
,``~' ly poor design. The use of a general purpose microprocessor
is expensive because of the provision, in tlhe microprocessor, of
capabilities, which must be paid for, but which are not employed
', in the opera~ion of the taximeter.
`~' It is therefore an object of the invention to provide
~:
, an electronic taximeter which overcomes the above difficulties.
It is a more speciflc object of the inventiorl to pro-
vide an electronic taximeter which incorporates more features,
``~ 30 and is competitive in cost and superior in performance to
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- mechanical taximeters.
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It is a still more specific object of th~ invention to
provide such an electronic taximeter which eliminates the high
cost and other difficulties of yeneral purpose microprocessors.
These, and other objects, are realised, in accordance
with the invention, by providing an electronic taximeter which
utilizes a dedicated microprocessor formed of discrete, off the
shelf and readily available microcircuits.
In accordance with a specific embodiment, a dedicated
microprocessor for a taximeter comprises: a) main memory means
for storing data at a plurality of storage locations therein;
b~ data memory means for receiving input data at a plurality of
storage locations therein, c) combining means for combining the
data of storage locations of the main memory means with the
input data of respective storage locations of the data memory
means for updating the main memory; d) program memory means for
controlling the operation of the data memory means, and comprising
a plurality of storage locations therein, e) counter means for
sequentially selecting the storage locations of said main memory
means and said program memory means, and f) clock means for
driving the counter means through its cycle.
The main memory means may comprise a random access
memory (RAM), and the data memory means and the program memory
- means may comprise, respectively, first and second read only
memory (ROM) means.
In a preferred embodiment, each of said storage loca-
tions of the RAM and the first ROM comprise four bits of informa-
tion whereby a single binary coded digit (BCD) can be stored at
-" each of said aforesaid storage locations, and said combining
means comprises a BCD adder.
The microprocessor may further include latch means
having an input connected at the output of said BCD adder, and
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an output connected to an input of sa.id RAM whereby upa~ted
data from said BCD adder is provided to said RAM.
The microprocessor may still further comprise an in-
put multiplexer having an output connected to an input of said
first ROM, said counter means being connected to said multi-
plexer: and input latches having an output connected to an in-
put of said multiplexer and having inputs connected to sources
of input data, said clock means being connected to drive said ..
input latches, whereby input data is provided to said first ROM
through said input latches and said input multiplexer in syn-
chronism with storage lGcation selection in said RAM.
. From a different aspect~ the invention relates to
a taximeter including a microprocessor as above defined and
further comprising: a selector circuit subsystem having an
~ input connected to the output of said latch means9 said selector
.~ circuit subsystem being driven by said counter means' the out-
put of said selector circuit subsystem being connection to an
input of a BCD to 7 segment converter: the output of said con~
, verter being connected to a display device, whereby parameters
selected on said subsystem are displayed on said display device
in synchronism with storage location selection in said RAM.
In accordance with a more specific embodiment, a
processor for an electronic taximeter comprises: A) a computer
; loop including, 1) a RAM having a plurality of updatable data
storage locations therein accessible by a like plurality of
. addresses; 2) a DATA ROM having a plurality of preset data
storage locations therein accessible by a like plurality of
aadresses, 3) a BCD adder receiviny inputs from both said
RAM and said DATA ROM to add the contents of predetermined
: 30 storage locations of both, 4) a PROGRAM ROM whose output is
-` fed to said DATA ROM, and 5) a latch receiviny the output of
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said BCD adder and feeding an input of said RAM to thereby
update said RAM with updated data from said sC~ adder; B)
~ input multiplexer means fed to said DATA ROM, C) means for
;` addressing said R~M, said PROGRAM ROM, and cycling said in-
put multiplexer means, said means comprising; 1) clock means:
and 2) electronic counter means and D) func~ion circuit means
including said counter and connected to said clock means for
signalling taximeter functions such as HIRED and TIME OFF
wherein, all calculations are performed in said computer
loop.
The invention will be better understood by an axam-
ination of the following description 9 together with the accom-
panying drawings, in which:-
FIGURE 1 is a block diagram of the electronicsportion of the taximeter,
FIGURE 2 is a schematic illustration of a transducer:
and
FIGURE 3 shows the front face of one embodiment of
a display device.
Referring to Figure 1, the taximeter in accordance
with the invention comprises a trnnsducer 1 for providing pulses
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at fixed units of distance travelled by the taxi in which the
taximeter is ins-talled. One embodlment of such a transducer is
shown in Figure 2 in which 3 is the transducer shaft which is
connected in series with the speedometer cable 5 of the taxi.
Four blades 7 are equally spaced around the shaft, and the blades
are disposed to pass in the path of light between light emitting
diode 9 and phototransistor 11. An output pulse is provided
from the phototransistor each time the path of light between
the LED and the phototransistor is broken by the passing of a
blade 7 therebetween. AS most speedometer cables are rotated at
an approximate rate of 1000 turns per mile (or kilometer) travel-
led by the taxi, the phototransistor will provide approximately
4000 pulses per mile (or kilometer) travelled.
Returning to Figure 1, the output of the transducer 1
is fed to one terminal of the input latches 13 which, as ~ell
known in the art comprises a plurality of bistable devices. A
second input terminal of 13 is fed from an EXTRAS pushbutton on
the taximeter input as will be described below. Another terminal
of 13 is connected to quartz time base generator 15 which acts
as the clock for the entire system. The frequency of 15 is of
the order of 2.5 MHZ .
The output of 13 is fed to input multiplexer 17, and
the output of the multiplexer is fed to data ROM 19.
Clock 15 also provides a timing signal to function
circuits subsystem 21 which comprises an electronic counter.
The count on counter 21 is increased by one each time a pulse is
supplied from clock 15 until the maximum count of the counter is
~` reached. At the next clock pulse, the counter returns to zero
to begin a new cycle.
The function circuits subsystem has one outpu-t connected
to the address terminals of the RAM 23, and the ad~ress on the R~M
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23 which is selected at any time Co~re~pon~S ko the count on ~1.
Thus, the ad~ress of RAM 23 is sequentially stepped an~ accessed
through its entire range in each cycle of the subsystem 21, as
the maximum count on 21 corresponds to the number of addresses
of ~AM 23. In a preferred embodiment, R~M 23 comprises 64
storage locations, each location storing ~our bits so that a
single binary coded digit can be stored thereat. In this ernbodi-
ment, 21 has a maximum count of 64.
The output o~ RAM 23, referred to as last data output,
consists o~ four lines connected to BCD adder 25, and the out-
put of 25 is fed to latch 27. AS will be seen below, new data
supplied to data ROM 19 is added to the last data of RAM 23 in
the adder 25. The new data is then fed to latch 27,and, in turn,
to RAM 23 to thereby update the data in RAM 23.
` In the preferred embodiment, above-mentioned, the RAM
23 is a 64 x 4 bit memory, and the connection between 21 and
23 comprises SlX parallel address lines. This same output from
21 is also fed to program ROM 29, and the function of program
ROM 29 is to control the operation of data ROM 19 and the remain-
der of the circuits as will be more fully described below. In
the embodiment described herein, the program ROM acts as a
'`look-up" table.
Function circuits 21 also sequence selector circuit
` subsystem 31 which receives data input from latch 27 preparatory
to feeding the data to display unit 33 where it can be visually
displayed. BCD to seven segment decoder 35 converts to BCD
representation to a code usable by the display unit.
Although shown as a separate unit in Figure 1, manual
select switches 37 are really a part of the display device.
Parameters to be d:isplayed on the display unit are selected by
activating the appropriate rotary switch or pushbuttons on 37 to
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prime appropriate addresses in the selector circuit to permit
; passage of the data at the addresses ~hrouyh to the ~isplay unit.
The front face of the display unit is illustrated in
Figure 3 and consists of a VACANT/HIRED switch 39, an EXTRAS
button 41, TIME ON/TIME OFF switch 43, and readout and rate
selector rotary switch 37. The display unit also includes a bank
of LEDs 47 which pro~ide a nine digit readout. The same reference
numerals in Figure 1 designate either lines from the appropriate
switches in Figure 3 or schematic representations of the same
elements.
, In an em~odiment not illustrated herein, the VACANT/
' HIRED and TIME O~/TIME OFF switches are replaced with a single,
3 position switch which operates under control of the following
fixed sequence:-
, HIRED ..... 1st, 4th, 7th ..... pushes
TIME OFF .. ...2nd, 5th, 8th .. ...pushes
`` VACANT .... .3rd, 6th, 9th .... ~ pushes.
The basic measurements which are performed by the
' taximeter are listed below in the order of increasing comple~ity:-
(a) Counting and storage of the total number of paid
trips as indicated by depression of the VACAMT/HIRED switch 43
at the start of each trip.
(b) Recording and storage of the extra fare or sur-
; charge (due to excess luggage for example) as entered by a
single or repeated depression of the EXTRAS button 41. The
EXTRAS display and storage are cleared before the start of each
trip and new data is entered if necessary only at the start of
;~ each trip.
i~ (c) Recording and storage of total extras, that is,
the total of all items (b) above for all trips.
(d) recording and storage of total miles (or kilometers)
travelled, i.e., basically the same funct:ion as an odometer of a
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car.
(e) Recording and storage o~ paid miles (or kilometers)
i.e., total miles (or kilometers) travelled during the time the
taxi is hired.
(f) Processing and recording of the fare, that is, the
fare for each paid trip. The fare processing is a significantly
more complicated function than any of the preceding items listed
above. On a typical trip, the following events occur to make up
the fare:-
(1) A drop fare is recorded when the VACA~T/HIRED
- switch 39 is depressed. The drop fare could amount to,
for example, 75~.
(2) When the taxi starts to move, it will first
traverse a l`dead zonell distance or time for which no
extra fare is charged. The distance could typically
be of the order of 1/4 of a mile.
(3) After the dead zone distance or time has been
traversed, and if the taxi is travelling faster than
a cross over speed as defined below, the fare is in-
cremented on the basis of a predetermined increment
per unit of distance travelled, for example, 12¢ per
l/S of a mile.
(4) If the taxi decreases the speed below cross
over or stops during the trip, the fare is incremented
at a predetermined rate per unit of time, for example,
5~ for each 30 second period.
(5) If the taxi starts again after a stop has
occurred, the fare continues to be incremented at the
time rate until the cross over speed is again reached.
The cross over speed is defined as the speed at which
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~ the rate of accumulation of distance based fare as in
- (3) is just e~ual to the rate of accumulation of time
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based fare as in (4), or it may be arbitrarily set to
, any speed in accordance with the local or municipal
rate structure legally in effect. -~
With the examples given above, i.e., a distance based
rate of 12~ per 1/5 of a mile and a time based rate
of 5~ for every 30 seconds, the cross over speed which
yields the maximum allowable revenue is 10 miles per
hour. In order to determine when the cross over speed
is reached, the meter compares actual with cross over
'
speed continuously and switches from distance based
increments to time based increments below the cross
` over speed and frorn time hased increments to distance
based increments above the cross over speed.
(6) The time rate is switched off by the driver
ii when he arrives at the destination of his fare by
: depressing the TIME ON/TIME OFF switch 43. At this
``- point, no further fare increments can be accumulated as
the timer mechanism is off and no further distance is
being covered.
`- 20 (7) The time rate may be switched off at any point
during the trip by depressing the switch 43 if fare is
to be charged solely on the basis of distance travelled.
~ (g) Total fares, that is, the sum of all items (f) above
`~ for all trips, is also calculated and stored and can be read out
" as required.
Method of Operation
`"' `
The operation of one embodiment of the invention will
now be described.
m The data ROM and the RAM, .in the described embodiment,
` 30 each comprise 64 memory locations with 4 bits each, or the for-
` mation of a single BCD digit, at each location. Current informa-
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tion is stored in the RAM, and new clata is computed by adding
the contents of ROM to RAM. The data in the RAM ig updated,
when the address a-t which this data is contained in the RAM is
; selected by the function circuits, by applying the data of the
RAM to one input of the scD adder. The new data is then applied
to the other input of the BCD adder, and the information at both
inputs is then processed in the adder.
The process data is then applied to the latch 27 where
; it becomes available for insertion, as updated data, to an input
terminal of the RAM 23. At the same time, the updated data is
available to be displayed on a display device by virtue of the
connection between the latch 27 and selector circuits 31.
The following examples indicate the computations and
manipulations for the various functions as above described:
EXTRAS (total)
The EXTRAS data is inserted into the dedicated micro-
processor by depression of a button 41 of the display. Each
time the button is depressed, the appropriate address of the
data ROM is activated. This address will contain a predetermined
BCD number, (equivalent, for example, to 15~) and this predeter-
mined amount will be added to the appropriate storage location
in the RAM through the BCD adder as above described. For example,
` if it is required to insert 45~ of EXTRAS, then button 41 is de-
pressed three times.
If the amount stored in the addresses of the EXTRAS in
RAM 23 is, for example, $1.25, then the digits 5, 2 and 1 would
'., '
be stored in 3 separate locations respectively in the RAM. These
digits will be presented, in sequence, to the BCD adder when the
locations at which they are stored in the RAM are selected by the
. . ~
function circuits.
Each depres,sion of the EXTRAS switch 41 causes one of
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the input latches 13 to be ~Iset~ to logical 1 from logical 0).
Thus, when the function clrcuits 21 produce the address of the
least significant digit (5 of the $1.25) the output of the input
multiplexor 17 is a logical 1 (due to the prior setting of the
EXTRAS input latch 13). The output of the input multiplexor
causes the appropriate address of the data ROM to be 5 as this
was the predetermined amount pre-programmed into the data ROM
at this location. The 5 of the data ROM and the RAM will be
added together to produce a 0 with a carry 1.
When the address of the middle significant digit of
the $1.25 is selected by the function circuits, the carry 1 will
be added to the ~ from the RAM and the second digit 1 from the
ROM by virtue of the operation of the BCD adder. The data ROM
location corresponding to the RAM location of the middle signif-
icant digit will always be a 1. The address of the data ROM
corresponding to the RAM location of the most significant digit
of the EXTRAS will always be a zero.
The numbers 0, 4 and 1 will be sequentially loaded into
the RAM 23 after the addition has been performed so that the data
at the EXTRAS locations of the RAMs will now be the updated
amount of $1.40.
If there is no EXTRAS input, then only 0 will be added
to the RAM data so that there will not be any change in the data
in the RAM.
The total EXTRAS locations of the RAM will be updated
by adding the contents of the totals locations thereto under the
control of the program ROM.
The RAM contents storing the EXTRAS amounts is cleared
at the start of each trip. The RAM conkents for the total EXTRAS
are cleared only during intentional clearing of the meter
statistics.
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TRIPS_(total)
Total trips refers to the -total number of paid trips
taken by the taxi during any period. If this is cleared at
the beginning of each day, then the amounts stored at the end of
the day will be the total number of paid trips taken in that day.
I~ this is cleared at the beginning of the week, then the amount
stored in the R~M at the end of the week will constitute the total
number of paid trips taken during the week.
Input data relative to paid trips is inserted by de-
pression of the HIRED button 39. This data is inserted throughthe function circuits 21, and when the HIRED button is pressed,
then the address of this information in the data ROM is activated.
The data ROM at the appropriate location will contain a BCD 1
so that each time the HIRED button 39 is pressed, the relevant
data at the locations in the RAM 23 will be incremented by 1.
MILES OR KILOMETERS (total)
The operation of the computing circuit for total miles
(or kilometers) travelled is very similar to the operations for
EXTRAS as described above. The basic difference is that the
input data comprises distance pulses arriving from the trans-
ducer 1 at a rate of approximately 4000 per mile (or kilometer)
travelled. Each pulse from the transducer sets a lldistance"
latch in the input latches, and the sequence of events for adding
this new data to the data already in the RAM 23 must all take
place before the next distance pulse arrives -from the transducer 1.
A total of 8 digits are used for calculating and storing
total miles (or kilometers) in the R~M. Thus, the maximum dis-
tance which can be stored is 99,999.999 miles (or kilometers).
As the transducer produces a distance pulse each time
30 the taxi travels 1/4000 of a mile (or kilometer), or every 0.00025
miles (or kilometer), obviously data cannot be loaded directly
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into the thir~ ~igi-t to the right of the decimal, i.e., into the
thousandth position. In ad~ition, calibration may be such that
a pulse is produced for a distance which is not exactly 0.00025
miles (or kilometers), that is, it can produce a pulse every
0.000247 miles (or kilometers) or every 0.000256 miles (or
kilometers). In order to allow for the use of a nominal 1/4000
mile (or kilometer) resolution, and in order to allow for a car
calibration variation, or even for a change from miles to
kilometers, 3 additional locations in the RAM are used, and
with each transducer pulse, the numbers 2, 5 and 0, representing
0.000250 miles (or kilometers), or appropriately different
numbers as discussed below, are added to respective ones of these
3 additional locations. A fourth additional location, comprising
an overflow location, is filled with a 1 each time there is an
overflow of the sum of the 3 additional locations, (i.e., the
sum is greater than or equal to 1000) and this 1 represents 0.001
miles (or kilometers).
For a car which produces exactly 1 pulse for every
1/4000 of a mile (or kilometer), corresponding locations in ROM
20 19 are pre-programmed (burned) with the numbers 2, 5 and 0,
representing 0.000250, or 1/4000 of a mile (or kilometer)~ If
the transducer produces pulses at a different rate, then different
numbers will be pre-programmed into the ROM. For example, if
the transducer produces 1 pulse every 1/3850 miles (or kilometers),
then the appropriate ROM locations will be pre-programmed to
contain the numbers 2, 6 and 0, representing 0.000260, or
1/3846th of a mile (or kilometer), which is an error by only
0.1% or one part in a thousand.
A car calibration is achieved by looking up the digits,
- 30 to be added to the additional locations in the RAM, in the
appropriate additlonal locations of the ROM 19 at the appropriate
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moment of the RAM/ROM/adder functional sequence. I'hese ~iyits
are then stored in the additional locations oE the RAM.
To convert from miles to kilometers, appropriately
different digits would be burned into the ROM locations. As a
kilometer is approximately 2/3 of a mile, the transducer pro-
duces a distance pulse approximately every 1/2665 of a kilometer
or every .00038 kilometer. Thus, -the numbers 3, 8 and 0 would
be burned into the appropriate ROM locations.
This is the only change necessary to convert from
mileage operation to kilometer operation.
The output of the overflow additional address of the
RAM will be added to the RAM address containing the thousandths
data total miles (or kilometers) travelled information whenever
there is a logical 1 at this overflow location. Thus, the infor-
mation concerning miles (or kilometers) travelled is updated in
the RAM addresses.
As will be appreciated, when the car is not moving,
distance pulses will not be produced by the transducer 1. At
this time, distance information of the RAM 23 cycles around the
computing circuit loop unchanged along with other data (which
is not necessarily unchanged) as the RAM is stepped through its
memory location by the function circuits 21.
As will be appreciated, the content of the ROM will be
applied only against the least significant digit (thousandths)
of the RAM for total miles (or kilometers) travelled. The only
time any of the other locations will be incremented is by a carry
from a lesser significant digit to a more significant digit.
PAID MILES GR KILOMETERS
The operation of this circuit is the same as for total
miles (or kilometers) except that in the case oE paid miles (or
kilometers), the accumulation is only done when the taxi has been
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hired and the HIRED button on the taximeter has been clepressed.
The accumulation of paid rniles (or kilometers) beyins when the
HIRED button is pressed and en~s, for any trip, when the VACANT
button is depressed afterwards.
FARES COMPUTATION
The operation of the computing circuit for fares is
more complicated than for the previous functions above describe~.
The fare for any ride is made up of the following elements:
(l) Drop fare - a fixed fee inserted at the beginning
of each paid trip when the VACANT/HIRED switch is
- depressed.
(2) Distance based fare - fee based on the distance
travelled by the taxi when the taxi is moving in excess
of a cross over speed.
(3) Tlme based fare - ~ee charged when the vehicle is
moving at a speed less than the cross over speed
(including not moving at all).
In addition to the complications of drop fare, time
based fare and distance based fare, there is the additional
element of l'dead zonel', which is defined as a fixed distance or
a fixed time after the beginning of a trip during which the
customer is not actually charged at the prevailing time or
distance fare. The presence or absence of dead zone, or the
actual amount thereof, is fixed by the applicable tariff regula-
tion authorities and is therefore separately adjustable for
different geographical areas in which any taximeter may be re-
quired to operate.
Five locations in the RAM are assigned to the storage
of fares data. Thus, the maximum fare which can be stored in
the RAM iS $999.99. ~1hen the VACANT/HIRED switch 39 is depressed,
and the taximeter goes into the HIRED mode, these five locations
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are cleare~ and the drop fare is ad~e~ ~rom 5torage lo~a~,ions ~r
this data from the ROM 19. This addition take~ place under the
control of the program ROM duriny the first cycle of the function
circuits after the depression of the button 39.
When there is a dead zone regulation in the area o~
operation, then dead zone locations will be assigned in the RAM
including an overflow dead zone location. The overflow dead
zone location will be filled (set to logical l) only after the
dead zone distance or time has been traversed ~y the vehicle.
Further fare accumulation will not take place until the overflow
dead zone location has been filled.
The amount by which the fare is incremented is pre-
programmed into memory locations in the ROM corresponding to
appropriate memory locations in the RAM. Thus, if the increment
is 5~ (say for every tenth of a mile (or kilometer), then the
nurnber 5 will be pre-programmed into a memory location in the
ROM corresponding to the least significant digit fares location
in the RAM. Each time a tenth of a mile (or kilometer) is
traversed, the memory location in the ROM will be activated to
be added to the corresponding location in the RAM on the next
pass of the function circuits. If the increment is 10~, then
the memor~ location in the ROM corresponding to the second least
significant digit location in the RAM will be pre-programmed
with a l.
The calculation of the miles (or kilometers) traversed
which are to be charged, or the time traversed when the vehicle
is either not moving or moving at below the cross over speed,
' is under the control of the program ROM 29.
TOTAL FARES COMPIJTATION
Five locations are provided in the RAM for the storage
of total fares. These locations are not cleared at the start of
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each trip but have to be deliberately cleared at the d1scretion
of the owner of the device.
The contents of the total fares addresses are continu-
ously updated in parallel with the fares addresses. This function
also comes under the control of the program ROM.
DISPLAYING PARAMETERS
As RAM 23 is continuously sequenced through all of its
64 addresses, each 4 bit 4 wire BCD digit is presented by latch
27 to display selector circuits 31. In order to select any
particular parameter, manual selector select switch 37 is rotated
to that selected parameter. The switch 37, in conjunction with
synchronizing signals from function circuits 21, select the
parameter to be displayed. Each BCD digit of that parameter is
decoded by the sCD to 7 segment decoder, and the decoder is
connected to light emitting diodes of 7 segments to display
any decimal digit as is well known in the art.
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