Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
POWER SUPPLY FOR COMPUTING MEANS WITH DATA PROTECTED S~UT-DOWN
BACKGROUND OF THE INVENTION
~iel~l ~.e ~I~A Inven~ n
The invention is in the field of data monitoring and re-
cording systems particularly adapted for use on vehicles.
Description of the Prior Art
Prior data recording apparatus has been utilized for re-
cording various engine parameters for use as diagnostic and
maintenance tools for land vehicles and aircraft. Additional-
ly, recording devices have been utilized in connection withinterstate truck travel to keep track of gasoline purchases in
various states to take advantage of tax rebates and the like.
Representative examples of these prior art devices as shown in
U.S. Patents 3,099,817; 3,964,302; 4,050,295; 3,864,731;
3,938,092; 3,702,989; and 3,792,445. Typically, these prior
art devices utilize either singly or in combination various
display means, manual input means, and recording means in the
form of either paper or magnetic tape. In some instances only
alarm indications are provided or pertinent data is displayed
as shown, for example, in U.S. Patents 4,050,295 and
3,964,302. In other cases entire vehicle performance data is
recorded as discussed in U.S. Patent 3,099,817. Attempts have
been made to reduce the amount of recording and consequent
tape usage by means of hardware and software selective data
recording such as disclosed in U.S. Patents 3,792,445 and
3,702,989.
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A particular disadvantage of these prior art devices
is their lack of versatility with regard to usage and
recording of data and a reliance upon bulky and expensive
magnetic or paper tape as a primary recording medium.
Of palrticular importance in utilizing data vehicle
monitoring recording apparatus is the necessity to keep
accurate track of time so that various malfunctioning
engine parameters may be exactly correlated with the time
of occurrence. Although various clocking techniques have
been developed in the prior art, such as, for example,
apparatus disclosed in U.S. Patents 4,031,363, 4,022,017
and 3,889,461, these systems do not provide the necessary
time tracking accuracy and reliability coupled with power
conservation needs required in land vehicles. In
particular, when a computing means such as a micropro-
cessor is utilized to selectively filter and store data as
well as provide a real time clock function there is a need
for maintaining a high accuracy in the real time clock
function despite inoperability of the microprocessor when
the vehicle engine is turned off. In this connection the
prior art has not addressed itself to the problem of
shutting down the microprocessor in an orderly fashion to
protect data being processed in the event of power failure
or engine turnoff.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to pro-
vide a versatile monitoring and recording system for pro-
viding accurate data parameters useful for record keeping,
performance and maintenance applications.
Yet another object of the invention is to provide a
monitoring and recording system utilizing a computing
means to read the various input parameters and selective-
ly ~tore pertinent input parameters in a memory.
To this end the invention consists of a device
monitoring and recording system comprising: a) sensing
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means for sensing device operating parameters and generat-
ing data signals corresponding thereto; b) computing means
for receiving and processing said data signal; c) memory
storage means for storing said processed data signals from
said computing means; d) power supply means for providing
power to said device, said computing means and said memory
storage means; e) said computing means comprising: i)
means for executing a data protect routine in response to
at least one of: (1) said data signals corresponding to a
shut-down condition of said device, and (2) a power-fault
signal corresponding to a power fault of said power supply
means; and f) said power supply means comprising: i) means
for receiving said shut-down command from said computing
means; ii) means for disconnecting said power supply means
from said device and said computing means in response to
said shut-down command; iii) means independent of said
computing means for disconnecting said power supply means
from said device and said computing means; and iv) means
for delaying operation of said independent disconnecting
means for a time period substantially greater than that
normally required for the computing means to issue said
shut-down command in response to said fault status signal.
Another object of a preferred embodiment of the
invention is to provide an on-board microprocessor
controlled vehicle monitoring and recording system for
selectively displaying and recording data in a random
access memory also located on-board the vehicle.
The preferred embodiment also provides an accurate
real time clock circuit in a vehicle monitoring and
recording system wherein an on-board microprocessor is
utilized to accurately track time when the engine is on
and a separate counting circuit is utilized for accurate
time keeping purposes when the engine is off. Means are
also provided for synchronizing the counting circuit with
the microprocessor counting circuit when the engine is
turned back on.
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Additionally, there is provided in accordance with the
teachings of the invention a method of protecting data
being processed by a computing means having a central
processing unit (CPU) and a memory storage means, said CPU
operable to sense vehicle operating power therefrom, said
method comprising the steps of: a) sensing at least one
vehicle parameter indicative of an engine shut-down
condition; b) sensing a power fault condition of said
vehicle battery; c) executing a data protect routine in
said CPU in response to one of said at least one sensed
shut-down condition and said power fault condition for
storing data being processed by said CPU into said memory
storage means; d) disconnecting said vehicle battery from
said CPU after completion of said data protect routine,
said CPU initiating said disconnecting step; e) sensing a
predetermined time interval substantially longer than the
time normally required for said CPU to execute said data
protect routine; and f) upon failure of said CPU to
initiate said disconnecting step, disconnecting said
vehicle battery from said CPU independently of said CPU.
In the preferred embodiment of the invention there is
provided a vehicle parameter monitoring, recording and
analyzing system comprising a plurality of sensors, a d~ta
processing and recording device, a portable data link and
a remote computing apparatus. The plurality of sensors
are positioned for sensing operating parameters of the
vehicle and for generating data signals in response
thereto. ~he data processing and recordiny devi.ce is
positioned on-board the vehicle and comprises a computing
means including a central processing unit for processing
the data signals, a program memory storage means for
storing an operting program from the central processing
unit, the central processing unit selecting some of the
data signals in accordance with predetermined criteria as
stored in the program memory storage means and a data
memory storage means for receiving and storing the selected
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data signals from the central processing unitO The
portable data link comprises a non-volatile memory of
substantially larger memory capacity than the data memory
storage means, a power generating means independent of the
vehicle for operting the non-volatile memory, means for
connecting the non-volatile memory to the data storage
means, means for reading the selected stored data signals
from the data storage means into the non-volatile memory,
means for disconnecting the non-volatile memory from the
data storage means, said non-volatile memory storage means
adapted for removal from the data link. The remote com-
puting apparatus comprises means for reading the selected
stored data signals of the non-volatile memory, means for
analyzing the selected stored data signals and means for
printing the analyzed data.
These and other features of embodiments of the
invention will become clear in connection with the fore-
going description taken in conjunction with the drawings
- wherein:
Figure 1 is an overall block diagram of the vehicle
monitoring and recording system;
Figure 2 is a block diagram of the on-board subsystem;
Figure 3 is a schematic diagram of the analog
interface;
Figure 4 is a schematic diagram showing an overview of
the digital interface;
Figure 5 shows a detailed schematic diagram of the
digital interface and the real time clock circuit;
Figure 6 is a block schematic diagram of the power
supply circuit; and
Figure 7 is a detailed schematic diagram of the
voltage sensing and control circuit of Figure 6.
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DETAILED DESCRIPTION OF THE PREFERRED EM~ODIMENT
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System Overview
A block diagram of the vehicle monitoring and
recording system 1 in accordance with the invention is
illustrated in Figure 1. The system has three major
components, namely, an on-board subsystem 2, a portable
data link 4 and a remote data processing subsystem 60 The
on-board subsystem 2 is indicated
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as being housed within a vehicle such as the cab of truck 8 and
is seen to comprise a plurality of sensors generally indicated
at 10, a data recorder 12 and a data monitor 14. The sensors
10 are positioned in various locations throughout the vehicle
and typically provide both analogue and digital signals to the
data recorder 10. The data recorder 12 is in turn intercon-
nected to the data monitor 14 so that the operator of the
vehicle may have access to the sensor data on a real time
basis. An input means such as a plurality of switches 16 are
provided on the data monitor to allow the operator to select
particular data for display means 18. The display means 18
may comprise, for example, a seven segment LED display. The
data recorder 12 may also comprise a plurality of switches 20
for manual input of data to be recorded. Switches 20 may in
fact comprise an entire keyboard so that digital data or coded
data may be fed into the data recorder 12. For example, when
the vehicle passes across a state line the operator may enter
a code representing the new state entered which will automat-
ically effect recordation of the time of day and odometer
reading to form a record for tax rebate purposes. Further,
switches 20 may comprise designated input keys such as a
"snapshot" key 22 which effectively enables the data recorder
to record all sensed data at that particular instant of time.
In this manner, the vehicle operator may override automatic
data recording at will as, for example, upon the occurrence of
an abnormal operating condition. The snapshot key 22 thus
permits recording of data at the instant the operator notices
an abnormal condition, thus permitting a correlation of the
time at which the condition occurred thus allowing for proper
reconstruction of the malfunction during off-line processing.
The data monitor 14 is not required for operation of the
system 1 and indeed, the apparatus may be employed only uti-
lizing the sensors 10 and data recorder 12.
The portable data link 4 is utilized to extract data from
the data recorder 12 and store same onto a magnetic tape means
24. A flexible cable 26 is provided with pin connected
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terminals to allow simple connect/disconnect capabiliti~s of
the data link 4 to the data recorder 12. Transmission of data
from the data recorder 12 to the data link 4 is achieved by a
read command provided by switches 20. The data link 4 may also
comprise display means generally indicated at 28 for display-
ing data stored on the magnetic tape means 24. Typically, the
data link 4 operates on its own battery source (not shown).
Further, the data link 4 may be provided with an optical dis-
play means to permit display of data on the magnetic tape
means 24.
Vehicle data on tape 24 is transmitted to the remote com-
puting subsystem 6 for detailed processing of the data origi-
nally stored in memory means of the data recorder 12. A number
of different paths for data processing are illustrated in
FIGURE 1. For example, the magnetic tape means 24 may be fed
to input means of a central computer 30 where data may be
sorted and formated for printing on printer 32. Alternately,
the data from the magnetic tape means 24 may be fed into input
means of a diagnostic console 34 where the data may be sequen-
tially viewed on display means thereof. For example, dataassociated with a particular day's operation may be scanned
without any prior sorting and utilized by mechanics as a diag-
nostic tool. The diagnostic console 34 may additionally be
utilized to provide the tape data to a printer 36 to provide
hard copies of the daily operating parameters. Yet addition-
ally, data from the magnetic tape means 24 may be applied to a
motor communication link M for transmission over telephone
lines T for subsequent feeding to a distantly located computer
38 and printer 40. It is clear that the cable 26 o`f the data
link may alternately serve as a means for reading the data
from tape means 24 into any of the processing channels set
forth in FIGURE 1.
The particular type of data that may be provided as an
output from the remote data processing subsystem 6 is illus-
trated hereinbelow. A particular example of a truck fleetreport may comprise three major sections, namely, a vehicle
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utilization report, a performance exception report and a
parameter pro~ile report. The vehicle utilization report may
comprise a summary of information which is related to the
modes of vehicle use over the reporting period and is t~pical-
ly reported on a daily basis. Such information may beprovided, as, for example, vehicle mileage, fuel consumption,
en~ine operating hours, average ~GP, average speed etc. The
information thus provided at the output of the remote data
processing subsystem 6 for this type of report is illustrated
in Table I. Thus, it is seen that on April 20, 1977 vehicle
No. 1234 consumed .1 of a gallon of fuel when the engine was in
idle and .3 of a gallon of fuel when the engine was operating
at road speeds. The relative inactivity of the vehicle on the
day in question is thus easily apparent. In this fashion, a
truck fleet manager has easy access of the daily activity of
each of a large number of vehicles. Total figures for the
period of time in question may also be provided. Vehicle
status codes are used to indicate which sensed parameters
exceeded their corresponding threshold values and the corre-
spondence of the vehicle status code with the sensed operatingparameters are indicated in Table II.
TABLE I
Vehicle No. 1234 Vehicle Trip Report 4/20/77 Thru 4/22/77
DATE ENG FUEL TOTAL AVE AVE VEHICLE
HRS GAL MILES SPD MPG STATUS
4/20/77 Idle.21 .1
WED Road.12 .3 .3 2.5 1.2
4/21/77 Idle6.101.9
Road17.67211.6951.0 53.8 4.5 D
304/22/77 Idle3.151.0
Road7.4979.2405.8 54.2 5.1 DE
_______________________________________________________
Total 9.46 25.28 294.1 1357.1 53.7 4.6 DE
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A representative example of the performance exception
report is shown in Table II. In this type of report only
abnormal vehicle operating parameters are recorded. For
example, on April 21, 1977, the battery voltage was seen to
reach a peak value of 13.5 volts which is above the normal or
threshold value in this case of 12.7 volts. The number of
times the battery exceeded the threshold value is also indi-
cated as well as the duration in hours during which such
excess existed. On the same day, oil pressure is seen to have
dropped to a peak low value of 2.5 PSI in comparison with a
threshold value of 20 PSI. Further, the oil pressure dropped
below threshold a total of five times for a total duration of
0.05 hours. (An asterisk next to the parameter measured indi-
cates a below threshold parameter.) Table II thus provides
valuable data that may be utilized for routine maintenance
purposes as well as to anticipate near future maintenance ad-
justments in addition to diagnostic testing and analysis.
It will also be appreciated that the storage of data
within the data recorder 12 is greatly compressed inasmuch as
the computer software performs a data threshold function so as
to store only the number of times a threshold is exceeded, the
time duration and the peak value. It is thus not necessary to
allocate large sections of memory or utilize large amounts of
magnetic tape and the like to continuously store all operating
parameters as is typical with prior art systems.
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TABLE II
Vehicle No. 1234 Abnormal Vehicle 4/20/77 Thru 4/22/77
Operation
VEHICLE PARAMETERS DATE DURA- # OF PEAK THRESH~
5 STATUS TION EVENTS VALUE OLD
D MPH 4/21/77 6.41 81. 81. 60.
D MPH 4/22/77 3.74 55. 72. 60.
E RPM 4/22/77 3.20 74. 2280. 1950.
0 Bat Vlt 12.7
4/21/77 16.66 1. 13.5 12.7
4/22/77 6.74 2. 13.5 12.7
1 Oil Pres* 20.0
4/21/77 . 05 5. 2.5 20.0
4/22/77 .03 3. 8.4 20.0
6 C. Pres* 10.0
4/21/77 16.20 4. .0 10.0
4/22/77 6.72 1. .0 10.0
7 Air Pres* 70.0
4/21/77 4.56 31. 18.0 70.0
4/22/77 1.67 47. 46.0 70.0
ING ON/OFF
4/20/77 4.
4/22/77 1.
The parameter profile report is illustrated in Table III.
Typically, the information provided represents a data snapshot
of all parameters at the particular time listed. The computer
module within the data recorder 12 may automatiaally record
data snapshots at various periodic times, as for example,
whenever the engine is turned off or, if desiredr at twelve
midnight of every day. In yet another example the computer
modules within the data recorder 12 may store a data snapshot
only if a programmed criteria is met, which criteria may in-
volve an interrelationship of a plurality of sensed vehicle
parameters. Specifically, a data snapshot could be taken
every hour if the vehicle is continually traveling over 30 mph
and the engine is revolving at greater than 1200 rpm during
the entire hour. This criteria will essentially ensure that
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the data snapshot corresponds to highway usage. Thus~ valu-
able specific data can be maintained to provide individual
dynamic vehicle histories for comparative studies providing a
unique source of data for maintenance and diagnostic use.
Further, by utilizing the snapshot key 22, the operator
may manually initiate a data snapshot recording whenever
desired, as for example, upon detection of some abnormal
running condition.
TABLE III
DATA SNAPSHOT - Vehicle No. 1234
PARAMETER DATE DATE DATE
4/21/77 4/21/77 4/22/77
TIME 2:30 6:39 1:16
MILEAGE 45.1 276.6 30.0
15 MILES PER GALLON 3.9 6.0 6.6
MILES PER HOUR 59. 57. 55.
RPM 1810. 1840. 1720.
BATTERY VOLTS 13.0 13.1 13.0
OIL PRESSURE 48.6 48.3 47.6
20 FUEL FILTER 2.0 3.0 2.3
COOLANT PRESSURE 3.0 5.0 3.5
AIR PRESSURE 75. 87. 86.
BRAKE TEMP 85. 68. 82.
COOLANT TEMP 158. 162. 159.
25 FUEL TEMP 39. 51. 62.
OIL, COOLANT LEVEL* 3 3 0
Legend -- Oil, Coolant Level*
0 - Both levels low
1 - Oil level low
2 - Coolant level low
3 - Both levels satisfactory
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On-Board Subsy~stem
A block diagram of the on-board subsystem 2 is illustrat-
ed in FIGURE 2. The on-board subsystem 2 is seen to comprise a
computer module 50, program memory 52, data memory 54, analog
interface 56, digital interface 58, power supply 60 and real
time clock circuit 62. The analog interface 56 receives
analog data from a plurality of sensors along lines generally
designated Al-Al6. Similarly, digital interface 58 receives a
plurality of input digital signals from digital sensing means
along lines generally designated Dl-Dll. It is clear that any
number of analog and digital sensors may be employed consis-
tent with the use requirements of the system.
The computer module 50 may comprise any of a number of
well known microprocessors currently available. For example,
a suitable device is the PPS-8 microprocessor including as-
sociated general purpose I/O, clock generator and memory units
manufactured by Rockwell International Corporation, Anaheim,
California. The program memory 52 may comprise, for example,
a programmable read only memory (PROM) and may be fabricated
utilizing PROM chips, Model No. NM5204Q. A plurality of
address lines are provided from the computer module 50 to
selectively address locations within the program memory 52.
Sequentially addressed locations provide instructions fed to
the computer module 50 governing the polling routine for the
sense data, threshold data selection requirements and the
like. The program residing in program memory 52 may be
tailored to specific user uses to govern the manner in which
the data is polled and the format of the data stored in data
memory 54.
Data memory 54 may comprise, for example, dynamic random
access memory (RAM) chips for permitting storage of processed
data from the computer module 50 and may be fabricated
utilizing thirty-two by one bit RAM chips, Model No. MM74C929.
A plurality of address and data lines interconnect the data
memory 54 to the computer module 50 to permit bidirectional
data transfer to selected memory addresses. A selected
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address within the data memory ~ay be chosen to serve as a real
time clock register.
A real time clock circuit 62 is ~lso provided on the on-
board subsystem 2 and is utilized to provide clock pulses to
the computer module 50 for time keeping purposes. Additional-
ly, the real time clock circuit 62 provides clock pulses to a
separate counter which forms part of the clock circuit and is
utilized to maintain accumulated time when the computer module
50 is shut down as, for example, when the engine is turned off~
A standby battery 64 is interconnected to the real time clock
circuit 62 as well as the data memory 54. When the engine is
shut down, the standby battery 64 is utilized to provide the
necessary operating voltages for the real time clock circuit
62 to power the separate counter contained therein. Further,
standby battery 64 maintains operating voltages to the RAM
chips within data memory 54 so that data memory 54 is effec-
tively a non-volatile memory. Normally, during engine operat-
ing conditions, power supply 60 supplies the necessary voltage
requirements to data memory 54 and real time clock circuit 62
as well as the other units residing on the on-board subsystem
2. Thus, system power is derived from the 12 volt vehicle
battery (not shown) and power supply 60 provides the necessary
power conversion, conditioning and regulation for distribution
to the various modules and sensors. A control line 66 is shown
connecting the computer module 50 to the power supply 60. The
control line thus permits microprocessor control of the power
supply shut-down to all modules, with the exception, of
course, of the data memory 54 and real time clock circuit 62
which are at that time supplied by the standby battery 64. The
computer module 50 thus senses ignition turnoff or power fail-
ures as high priority interrupts and the normal activity of
the microprocessor is suspended in favor of a data protect or
shut-down routine. After all data being processed is properly
stored, the last instruction of the shut-down routine effec-
tively implements the power supply shut-down (via line 66)
which in turn shuts down power to the computing module itself.
This mode of contxolled shut-down assufes safe preservation of
critical data regardless of the cause of the power loss. Data
is likewise preserved prior to a CPU directed power shut-off
in response to a sensed engine-off condition.
Analog_ nterface
A block diagram of the analog interface 56 is shown in
FIGURE 3. Typically, each analog channel provides a differ-
ence input signal to a voltage comparator 70, as for example,
National, Model No. LM124AN. Each of the voltage comparators
is identified by a channel suffix to designate the correspond-
ing analog input channel. It is also noted that each voltage
comparator 70 has a corresponding reference potential input
which may be individually set at a desired voltage level.
Noise discrimination filters and gain control resistor cir-
cuits may also be provided (not shown). Each of the outputs ofthe voltage comparators 70 are fed to a sixteen channel analog
multiplexer 72 (as for example two eight channel data selec-
tors, Model F34051) where the analog data is sequentially se-
lected and fed to an analog-to-digital converter 74. The con-
verted digital data is then fed to the computer module 50 forfurther processing. Diqital Interface - Overview
FIGURE 4 is a schematic diagram of the digital interface
58. Two representative digital channels are illustrated cor-
responding to a first channel providing sensed data along lineD1 and a last channel providing sensed data along line Dll.
The channel associated with line Dl is shown to comprise a
filter 80, comparator 82, flip-flop 84 and tri-state buffer
86. After filtering of the data in filter 80 the data is
compared to a reference voltage source which is utilized to
discriminate the sensed data signal from noise levels. The
output of comparator 82 is then utilized to set flip-flop 84
which remains set until reset by the microprocessor along
reset line RL-l. The microprocessor may select the output
35 from channel 1 as well as the remaining channels by means of
enabling the tri~state buffer 86 via a control signal along
line DIM select (digital interface module-select). The
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channel associated with the digital sensor having an input
along line Dll likewise comprises a filter 80, comparator 82
and tri-state buffer 86. In this case, however, the flip-flop
84 is not utilized. These channels typically represent signal
levels which do not change very often and consequently do not
have to be latched in a flip-flop. As before, prefixes have
been utilized to designate the channel associated with the
various devices 80, 82, 84 and 8~.
Digital Interface - Detailed Description
Real Time Glock Circuit
A more detailed circuit diagram for the digital interface
58 is shown in FIGURE 5. Also illustrated in FIGURE 5 is a
schematic diagram for the real time clock circuit 62. Each
channel of the digital interface circuit 58 is seen to com-
prise a filter 80, comparator 82, flip-flop 84, tri-state
buffer 86 and a programmable divide by N counter 87. The
programmable divide by N counter is utilized for relatively
high frequency input signals as, for example, engine RPM and
provides a single output pulse for a programmable number of
input pulses. Effectively then, counter 87 slows down the
pulse rate for high frequency input signals, These devices,
namely devices 80, 82, 84, 86, and 87, interconnected as a
unit shown in the Figure form a digital channel interface
circuit generally designated 90. Identical circuits are pro-
vided for each of the signal channels D2-D7 with small changes
as shown associated with the latch reset lines LR7 and LR8
associated with channels 6 and 7 respectively. A similar but
not ~uite identical digital interface circuit is shown at 92
associated with input signals D8-Dll. The difference between
the digital channel interface circuits 90 and 92 is simply the
removal of the flip-flop and the former circuit (See also
FIGURE 4).
The DIM select signal is an address decode off of the
address lines of the computing module 50 and is normally low
(logical zero or zero volts) to pass therethrough the signals
from the data input lines Dl-Dll. When the DIM select signal
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goes high, the tri-state buffers are placed in a high im-
pedance state with the buffer outputs left floating. As such,
additional signals interconnected to the output terminals of
the buffers 86 may be utilized to feed the input data lines to
the central processing unit (CPU~ of the computer module 50.
Thus, signals tied to the outputs of buffers 86-8, 86-9, 86-10
and 86-11 may be passed to the data input lines of the CPU
whenever the DIM select signal is not low, e.g. whenever the
DIM signal is present. In this fashion, the tri-state buffers
86 may be utilized to multiplex various signals into the data
lines of the CPU. The data input terminals in FIGURE 5 are
identified as BLl-BL8 and B9-B12. Reset signals to the flip-
flops 84 are fed by the CPU after reading data along terminals
BLl-BL8 to reset the corresponding flip-flops 84.
The real time clock circuit 62 is utilized to provide
clock signals which are received either by the computer module
50 or by a separate counter in the event that the computer
power is turned off, e.g. the vehicle ignition is off. Thus,
the real time clock circuit is seen to comprise a crystal
oscillator 100 which provides clock signals of 4.194 MHz to a
frequency division and conditioning network 102 as, for
example, Interse:l Model No. lMC7213. The frequency division
and conditioning network 102 divides the crystal clock signals
to provide a 16 Hz clock signal along line 104 and a 1 ppm
signal along line 106. The 16 Hz clock signals along line 104
are fed to flip-flop 108 and through tri-state buffer 110 to
the data terminal BLl for input to the computer module 50.
Normally, the DIM select signal is low thus enabling a contin-
ual source of l~Hz clock signals utilized by the computer
module 50 for real time clock tracking purposes.
The one pulse per minute (ppm) clock signal is fed from
the frequency division and conditioning network 102 to a five
stage decade counter 112 which may be, for example, ~otorola
Model No. 4534. The five stage decade counter counts the 1 ppm
pulses and sequentially reads each digit out as a binary coded
decimal (BCD) along lines 114a-114d. The BCD digits from
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decade counter 112 are thus provided at terminals B9-B12 and
are multiplexed into the data bus of the computer module 50
upor. the occurence of the DIM signal. It is noted, however,
that decade counter 112 is continually reset by the reset line
from the computer module 50 at terminal LRl whenever the CPU
of the computer module 50 is operative. Thus, whenever the
ignition is on and the vehicle is operating it is a function of
the computer module 50 to keep accurate real time and the
decade counter 112 is continually reset along terminal LRl and
line 116.
The 16 Hz is also fed along line 118 to one input of NAND
gate 120. A second input of the NAND gate 120 is provided by a
power status signal supplied from the power supply 60. The
power status signal is normally high (logical 1 or 5 volts)
when the power supply is operating at acceptable voltage
levels. Consequently, the output of NAND gate 120 provides an
interrupt signal to the CPU in time synchronism with the 16 Hz
clock signals. Upon receipt of the interrupt signal the CPU
of the computer module 50 examines the signal from input ter-
minal BLl and, if a clock signal exists the interrupt isinterpreted as a clock signal interrupt. As such, the com-
puter software updates the real time clock and resets the
clock flip-flop 108. The polling time for the CPU to cycle
through all of the digital as well as analog input signals is
typically on the order of 4 ms. ~n interrupt signal is, of
course, serviced at the highest priority. If a clock pulse
does not exist a:Long the data line associated with the input
terminal BLl then the software program governing the computer
module 50 interprets the interrupt as a power failure condi-
tion and a data protect or shut-down sequence is instituted.
When the vehicle ignition is turned off all power to the
system is terminated with the exception of power provided by
the standby battery 64 to the real time clock circuit 62 and
data memory 54 (See FIGURE 2). It iæ important to note, how-
ever, that it is the CPU which is responsible for the powershut down to the on-board subsystem 2. Thus, as seen in FIGURE
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5, the standby battery power is fed along line 122 to the
decade counter 122 as well as the frequency division and con-
ditioning network 102. As such, the 1 ppm pulses are con-
tinually stored in the five stage decade counter 112 and thus
maintain accurate time even though the engine is inoperative.
It is further pointed out that this time keeping function is
maintained even if the vehicle battery is completely removed
as may be entirely apprGpriate during a maintenance procedure.
The standby battery 64 may typically be housed on the RAM
memory board of the data memory 58 and is not effected by
removal of the vehicle battery.
After the vehicle is started and power is again supplied
to the computer module 50 as well as the other units of the on-
board subsystem 2, it is necessary to update the real time
counter residing in the data memory 54. Typically, when the
computer is operative one or more memory locations within the
data memory 54 will be utilized to provide the real time keep-
ing function. When the computer is turned off these data
memory locations are no longer operated but the information is
nevertheless preserved by means of the standby battery 6~,
e.g. the memory is non-volatile. It is consequently only
necessary to add to the contents of the real time clock
counters within clata memory 54 the time increment during which
the CPU was inoperative i.e. the time increment during which
the vehicle engi~e was turned off. Inasmuch as a five stage
decade counter only counts in increments of minutes it is
necessary to update the real time clock registers in data
memory 54 at the exact time at which the one minute pulse
increments the register. Thus, the updating of the real time
counters is done when the five stage decade counter increments
to the next succeeding minute. At most, it can take only one
minute in order to bring the real time clock residing in the
data memory up to date. The computer program memory residing
in program memory 52 directs the computer module 50 to contin-
ually examine the least significant bit of the decade counter112. The BCD digits are fed to the data bus of the CPU along
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lines 114a-114d when the engine is first started up and the
CPU continually issues a DIM signal to provide a continual
sequential readout of the date from decade counter 112. All
of the digits which sequentially appear on lines 114a-114d are
stored in a temporary time register within the data memory 54.
The least significant bit of this temporary time register is
continually monitored by the CPU and upon a one increment
change thereof the time interval in the temporary time regis-
ter is utilized to update the real time registers of the data
memory 54. At this time the DIM signal is removed and the DIM
select signal is consequently generated to enable passage of
the 16 Hz clock signals to pass to the CPU. In this fashion,
the contents of the decade counter 112 are utilized to main-
tain an accurate real time counter within the CPU even though
the counter 112 counts at rather large increments of 1 ppm.
Synchronizing the transfer o~ the counter 112 to the real time
registers within the data memory 54 enables accurate real time
tracking even after temporary inoperability of the CPU.
Power SuP~ly Circuit
FIGURE 6 is a block schematic diagram of the power supply
60. The power supply 60 is seen to comprise a filter F, power
transistor Ql and voltage regulators VRl-VR3. Typically, the
vehicle battery supplies a 12 volt signal to the emitter junc-
tion of power transistor Ql. The base of transistor Ql is
connected by means of a line 150 to a voltage sensing and
control circuit 152 which is further described in connection
with FIGURE 7. :Essentially, voltage sensing and control cir-
cuit 152 operates to turn on and off the power transistor Ql.
In turn, power transistor Ql is connected for operating
voltage regulators VRl-VR3 to provide various output voltage
signals along lines 154, 156, 158 and 160. These lines
provide respectively voltage levls of -12 v, +12 v, +5 v and +8
v. These voltage levels are utilized to power the various
other circuits illustrated in FIGURE 2. It is important to
realize, however, that all voltage levels are essentially
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controlled by the power transistor Ql which in turn is con-
trolled by the voltage sensing and control circuit 1520
A first input to the voltage sensing and control circuit
152 is provided by means of a line 162 which directly supplies
S the vehicle battery voltage which is subsequently sensed in
circuit 152. A further input of the voltage sensing and con-
trol circuit 152 is provided by an external start signal along
line 164. This signal is provided from the ignition switch
and is present whenever the ignition switch is turned on and
the engine is in the cranking mode. A further input to the
voltage sensing and control circuit 152 is provided from the
central processing unit of the control module 50. This signal
is the shut-down command provided along a line 166. This
command is issued by the CPU of the computer module 50
whenever the detected battery voltage level is below
acceptable limits or whenever the CPU detects an engine shut-
down condition as for example when the engine is manually
turned off. The voltage sensing and control circuit 152 pro-
vides a power status signal to the CPU of the control module 50
along line 16~. This signal is normally high (nominally 5
volts) but goes low upon detection of an abnormal battery
voltage condition. It is this signal, the power status
signal, that essentially initiates a data protect or shut-down
sequence within the CPU. After the shut-down sequence is
completed the CPU then issues the shut-down command to the
voltage sensing and control circuit 152 which subsequently
turns off the power transistor Ql thereby shutting down the
entire power supp:Ly.
A schematic diagram of the voltage sensing and control
circuit 152 is illustrated in FIGURE 7. The voltage sensing
and control cir uit 152 is seen to comprise a plurality of
voltage comparators, Ul-U4 and transistors Q2 and Q3. A
number of reslstors, Zener diodes and diodes are also provided
interconnecting the various elements as shown.
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The power status signal along line 168 is indicative of
the status of the power supply, namely, the vehicle battery
power supply which is nominally 12 volts. The 12 volt battery
signal is fed into the voltage sensing and control circuit 152
along line 162 and is connected to the positive input of the
voltage comparator U3. The output of voltage comparator U3 is
normally 5.1 volts maintained by the Zener diodes at the out-
put thereof. Thus, the normal status of the power status
signal is a logical l corresponding to the S volt output of
comparator U3. However, the output of comparator U3 will go
to zero whenever the voltage magnitude at the minus input is
larger than that at the positive input. This condition occurs
when the vehicle battery voltage drops below acceptable levels
which may, for example, he set at a threshold of approximately
5 volts. The threshold may obviously be selected by means of
the resistors dividing the voltage to the inputs of comparator
U3. Comparator U3 thus provides a means to sense the vehicle
battery source and provide an output signal, the power status
signal indicative of the acceptable or unacceptable condition
of the vehicle battery. If the power status signal drops to
zero volts, the CPU of the computer module 50 will initiate a
data protect ancl shut-down sequence and subsequently issue a
shut-down command over line 166.
The operation of the voltage sensing and control circuit
152 may be besl: understood by assuming initially that the
vehicle engine is turned off. Under such circumstances, the
external start signal along line 164 and representative of an
ignition on condition is a logical zero corresponding to 0
volts. This 0 volt signal is fed to the positive input of
voltage comparator Ul~ However, the negative input of voltage
comparator Ul is at a higher potential than the positîve input
inasmuch as this input receives a divided voltage from the
vehicle battery source, e.g. non-zero. Under these circum-
stances the voltage comparator output is low thus forcing the
output of voltage comparatoL U2 to be also low. The zero volt
output of voltage comparator U2 is fed via lines 170, 172 and
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174 to the base of control transistor Q3. The zero volt on the
base of transistor Q3 maintains the transistor in a non-
conducting state. The collector of transistor Q3 is con-
nected, however, via a line 150 to the power transistor Ql
(see FIGURE 6). Consequently, whenever the control transistor
Q3 is off the power transistor Ql will likewise be off and no
power will be delivered to the system.
Let us now assume that the operator of the vehicle turns
on the ignition switch and consequently causes the external
start signal on line 164 to go high. This high signal is fed
to the positive input of voltage comparator Ul forcing its
output high and forcing the output of voltage comparator U2
high. In turn, control transistor Q3 turns on giving power to
the entire system including the CPU of the computer module 50.
After the CPU of the computer module 50 is energized a normal
polling sequence examines the power status signal on line 168.
Assuming that the vehicle battery source is within acceptable
limits, no shut-down signal will be issued. The shut-down
command along line 166 is 0 volts to force a shut-down, and
nominally 5 volts when no shut-down is desired. Consequently,
a 5 volt signal is fed from the CPU of the computer module 50
along lines 166, ]72 and 174 to the base of control transistor
Q3. Consequently, even after the operator has released the
ignition key, the control transistor Q3 will be maintained on
since the base voltage is now supplied by the CPU itself which
has subsequently been brought up to power.
The CPU may now detect a shut-down condition as, for
example, by means of one of the digital or analog sensors. For
example, engine rpm may be continually monitored and the
absence of an rpm signal triggers the CPU to enter the data
protect and shut-down mode. At such time, a 0 volt signal is
applied as the shut-down command along lines 166, 172 and 174
to turn off control transistor Q3 and subsequently turn off
the power transistor Ql. Nominally a power off condition is
detected during a typical polling sequence which may last on
the order of 4 ms and the data protect and shut-down routine
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proceeds immediately in response thereto.
The shut-down command may also be given by the computer
module 50 in response to a battery failure condition which
would be detected ~y the CPU by means of the power status
signal on line 168. An additional shut-down procedure is also
provided in the event of excessive battery drain by means of
voltage comparator U4 and transistor Q2. Normally, when the
output of voltage comparator U3 is high (corresponding to an
acceptable operating condition) the output of comparator U4 is
low and thus transistor Q2 is non-conducting. However, when
the vehicle battery voltage is inadequate (below 5 volts for
example), the output of voltage comparator U3 goes to 0 volts
thus forcing the output of voltage comparator U4 to a high
state. The output of voltage comparator U4 turns on transis-
tor Q2 which in turn turns off the control transistor Q3 thusshutting down power. It is important to note, however, that
voltage comparator U4 does not change state instantaneously in
response to a low voltage signal at the output of voltage
comparator U3. In effect, capacitor C connected at the nega-
tive input terminal of voltage comparator U4 maintains a highvoltage at the input to the negative terminal thus maintaining
the output of U4 in a low state for a time delay roughly on the
order of 1-2 seconds. This time delay is effective to permit
the CPU of the computer module 50 to detect the power status
signal (which immediately goes to 0 volts as per the output of
voltage comparator U3) and initiate the data protect and shut-
down sequence. If the CPU is operating properly through the
entire shut-down routine the CPU itself would issue the shut-
down command well in advance of the time delay supplied by
capacitor C. However, in the event that no shut-down command
ever gets issued, the voltage comparator U4 and transistor Q2
insure that after the time delay the control transistor Q3
will be turned off thus shutting down power to the system.
The word vehicle as utilized herein and in the appended
claims is not intended to be restricted to truck but generally
applies to all forms of vehicles including by way of example,
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boats, airplanes, trains, tractors, off-highway machines, etc.
More generally, a "device" utilizing the principles of the
invention is intended to encompass not only vehicle but sta-
tionary apparatus such as, for example, generators, engines,
plant and process control systems, numerically controlled ap-
paratus and all forms of measuring and testing equipment.
Although the invention has been described in terms of
specific preferred embodiments, the invention should not be
deemed limited thereto, since other embodiments and modifica-
tion will readily occur to one skilled in the art. It istherefore to be understood that the appended claims are in-
tended to cover all such modifications as fall within the true
spirit and scope of the invention.
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