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BACKGROUND OF THE INVENTION
The present invention relates to apparatus for determining and storing, in
a non-volatile, substantially permanent memory, certain statistical
information. More particularly, the invention concerns apparatus for
accumulating (counting) the occurrences of different types of events and
storing these counts in substantially permanent form.
There are many situations in which the occurrences of events of different
types are to be counted to create statistical data in the nature of a
historical profile. For example, it would be desirable to record a "milage
histogram" of a motor vehicle, such as an automobile. Although most motor
vehicles have a mechanism (either mechanical or electronic) called an
"odometer" for permanently recording the total number of miles that the
vehicle has been driven, this data (total miles) is not very informative
about the condition of the vehicle. Data concerning the length of the
trips that the vehicle has been driven would be also very valuable in
evaluating the condition of the vehicle and in determining the vehicle
accident potential for the calculation of premiums in automobile
insurance.
Thus, in addition to an odometer which registers only the total miles
driven, it would be desirable to provide means for permanently recording
the "driving history" of the motor vehicle--more specifically, information
about the number and types of trips traveled by the motor vehicle--during
the life of the vehicle. As an example, the trips may be classified into
different trip lengths; namely, trips of one mile or less; trips of one to
two miles; two to three miles, etc. By separately counting the numbers of
trips in each type or category (e.g., three mile trips), a "milage
histogram" may be developed during the life of the vehicle. At the time of
resale of this vehicle, this milage history would indicate to a
prospective buyer the condition of the vehicle, thereby assisting both
buyer and seller in determining an appropriate purchase price.
Other types of events for which statistics may be kept are numerous and
varied. For example, in the case of a motor vehicle or an airplane, it may
be desirable to accumulate statistics about the number of hours running
time of the engine (event) at the different possible running speeds of the
engine (type of event). For example, it may be desirable to know how many
hours an engine was operated in the different speed ranges of 500-1000
RPM; 1000-1500 RPM; 1500-2000 RPM; . . . etc.
Statistics of this type are not limited to vehicles or engines, however.
For example, it may be desirable to accumulate statistics about the use of
electricity over a certain period of time (event) such as KWH/month during
the period of the year or during the period that a total number of
kilowatt hours are consumed. In this case, the KWH consumed for one month
(event) may be classified into different "slices" of power consumed (type
of event) such as 50-100 KWH/Mo.; 100-150 KWH/Mo.; 150-200 KWH/Mo . . .
etc.
Still another example of an "event" involves the notes played by a musical
instrument, such as a piano or organ, over the life of the instrument or
even during the playing of a single musical composition. In addition to
the total number of notes played, it would be desirable to know the
relative frequencies with which the individual keys of the instrument are
struck. Thus, the type of note (A, B, C, D . . . etc.) becomes the type of
event.
In accumulating statistics of the above-mentioned kind, it would be
desirable to store these data in a non-volatile memory in a substantially
permanent manner so that the contents of the memory cannot be easily
changed or tampered with. Thus, for example, the use of a conventional
random access memory would permit the accumulated data to be readily
changed so that the data could easily be falsified.
SUMMARY OF THE INVENTION
An object of the present invention is to provide apparatus for determining
the number of occurrences of a certain event which may be categorized into
different types of events.
A further object of the present invention is to provide apparatus for
determining into which type or class each particular one of a plurality of
events should be classified.
A further object of the present invention is to provide apparatus for
obtaining the type of statistical information mentioned immediately above
and for storing this information in substantially permanent form.
These objects, as well as further objects which will become apparent from
the discussion that follows, are achieved, according to the present
invention, by providing (a) a logic element for determining both the
occurrence of an event and the type of such an event, and (b) a
non-volatile memory, associated with and connected to the logic element,
for accumulating and substantially permanently storing the statistical
information.
In a preferred embodiment of the present invention, the memory may comprise
a "fusable-link", programmable read-only memory (PROM) in which stored
bits, all originally all set to their "0" state, may be destructively
"burned" into their opposite state. Since the states of the bits may be
changed only once, this type of memory offers complete security against
unauthorized changing of the statistical information.
As an alternative, an erasable PROM (EPROM), for which the contents may be
changed by the application of ultraviolet light, may also be used,
provided that the EPROM is manufactured without the usual UV light window,
or its UV light window is rendered opaque.
Other types of electronic or mechanical memories may also be employed with
the present invention. The criteria for such a memory are that it be
"non-volatile" (that is, that the memory be capable of retaining its
stored contents even when power thereto is removed); that the memory
comprise a plurality of bit storage locations with all of the bits stored
in the locations being originally set to the same, first logical state
(e.g., 0); and that the memory comprise memory control means for setting
the bits in selected ones of the bit locations to their opposite logical
state (e.g., 1). The memory control means must be capable of changing the
state of each bit only once so that, when the bits are set to their
second, opposite state, they are substantially permanently stored.
For a full understanding of the present invention, reference should now be
made to the following detailed description of one preferred embodiment of
the invention and to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a representational diagram of the contents of a programmable
read-only memory, illustrating the memory organization as well as the
principle of operation of the present invention.
FIG. 2 is a block diagram of a microprocessor based circuit, according to a
preferred embodiment of the present invention, for accumulating and
permanently storing the numbers of trips travelled by a motor vehicle,
where the trips fall into mileage categories.
FIGS. 3A and 3B are flowcharts of a firmware routine called "Permanent
Counter Initialization" used in the microprocessor in the apparatus of
FIG. 2.
FIGS. 4A and 4B are flowcharts of a firmware routine called "Prepare to
Burn Bit" used in the microprocessor in the apparatus of FIG. 2.
FIGS. 5A and 5B are flowcharts of a firmware routine called "Output" used
in the microprocessor in the apparatus of FIG. 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
A preferred embodiment of the present invention will now be described with
reference to FIGS. 1-5 of the drawings.
FIG. 1 illustrates how a programmable read-only memory may be organized to
record the number of trips travelled by a motor vehicle in different
milage categories. In this case, the memory can store 16,777,216 bits
total, organized as 1024 bits deep and 16,384 bits wide. It is capable of
recording trips of any length up to and including 1024 miles, with the
maximum number of trips in any category being 16,384. In the example
shown, the PROM has recorded 5 one mile trips, 4 two mile trips, 2 three
mile trips, 3 four mile trips, etc., thus providing a "histogram" or
milage history of a motor vehicle as outlined by the heavy line 10.
In the nomenclature which will be used herein after, the 1024 possible
categories of trips are stored in 1024 "bins" in the PROM. The proper bin
is found by a PROM "address pointer" 12. Within each bin, the memory
contains a plurality of bytes (2048 groups of 8 bits). Originally, all of
the bits contained in each bin are set to 0. The memory is designed to
permit one change of state of every bit--namely, from 0 to 1--by
appropriate application of signals to the memory address, data and control
inputs. Once a bit has been set to 1, however, its state cannot be changed
again.
At any time, the contents of the memory--that is, the states of all the
bits--may be read out via the data outputs by appropriate application of
address and control signals to the address and control inputs,
respectively.
Memories of the above-described type are commercially available. Such
memories are known as "fusable link" programmable read-only memories or
"ultraviolet light erasable" programmable read-only memories. Memories of
the latter type can be secured against erasure of the stored data by
packaging the semiconductor chip in a dual in-line (DIP) package without
an ultraviolet light window.
A suitable memory of the EPROM type is the TMS 2564 JL, manufactured by
Texas Instruments, Inc., Dallas, Tex. 75265. Since the TMS 2564 is an
8K.times.8 (65,536-bit) memory, a plurality of such memories would be
necessary to store the trip data described above. For example, five
565,536-bit (64K) memories may be used with their contents organized in
the manner shown in the following table:
______________________________________
NUM-
BER TOTAL
PROM OF BIN OF MILE
# PURPOSE BINS LENGTH BITS RANGE
______________________________________
1 very short
4 16,384 65,536 1 to 4
trips
2 short trips
16 4,096 65,536 5 to 16
3 medium 64 1,024 64,536 17 to 64
trips
4 long trips
256 256 65,536 65 to 256
5 very long 1024 64 65,536 256 to 1024
trips
______________________________________
This memory organization takes advantage of the fact that a motor vehicle
obviously travels most frequently on very short trips and travels very
seldom on very long trips. Some prior knowledge of motor vehicle trip
statistics would be helpful to provide the most efficient organization of
memory while avoiding the possibility of overflow.
A preferred embodiment of apparatus for accumulating and permanently
recording data concerning the trip miles travelled by a motor vehicle is
illustrated in FIG. 2. Starting in the upper left corner of this figure,
FIG. 2 shows an electronic sensor 20 arranged at the output shaft of the
vehicle transmission 22 which produces one signal pulse for each
revolution of this shaft. The signal is passed to a divider 24 which
counts the input pulses and produces one pulse on its output line 26 each
time the vehicle has travelled one mile. The signal on line 26 is passed
both to a resettable digital counter 28 and to a "permanent counter" 30.
The purpose of this permanent counter will be explained below. The counter
28 produces a 10-bit parallel digital signal on its output lines 32 which
is supplied to a microprocessor 34 via an I/O port 36. The microprocessor
thus receives a running count of the miles travelled by the vehicle during
each trip, starting at zero at the beginning of the trip.
The counter 28 is reset to zero each time the ignition switch 38 is turned
off. To avoid restarting the counter 28 from zero when the ignition switch
is turned off only momentarily, as when the vehicle is stalled in traffic,
a timer 40 is provided which produces a reset pulse thirty seconds after
the ignition switch is turned off. If the ignition switch is turned off
and subsequently turned on again before the timer 40 "times out" at the
end of the thirty second interval, the timer 40 does not produce an output
pulse.
The ignition switch 38 is also connected via an inverting amplifier 42 to a
second timer 44. This timer 44 produces an output pulse 30 seconds after
the ignition switch has been turned on. The pulse, so produced, is passed
to the permanent counter 30 to cause it to load an initial count received
from the microprocessor 34 via an I/O port 46. The contents of the
permanent counter 30 are indicated by a display device 48.
After a number is loaded into the permanent counter 30, this number is
incremented by the pulses provided on line 26 (one pulse per mile). These
pulses are also supplied to a temporary counter 50, the contents of which
are indicated by a display device 52. The contents of the temporary
counter may be manually reset to zero by pressing an operator reset button
54.
A bank of five UV-erasable, programmable read-only memories 56 are
connected to the address and data busses of the microprocessor 34. The
particular PROM to be read from or written to is selected by a decoder 58
which converts a 3-bit code received from the microprocessor 34 on lines
60 into a pulse on one of its output lines 62.
At the conclusion of a trip, after the ignition switch has been turned off
and the timer 40 produces a 5 volt pulse, as is indicated in the lower
left-hand corner of FIG. 2, this 5 volt pulse is converted to a 25 volt
pulse by a DC-to-DC converter 64. This 25 volt pulse is applied to the
V.sub.pp inputs of all of the PROMS 56; however, only that PROM which is
selected by the decoder 58 by a signal at its "chip select" (CS) input
will be written to. Within this selected PROM, a single bit, at the
location defined by the signals on the address and data busses of the
microprocessor 34, will be "burned" for permanent storage.
The microprocessor 34 is responsive to interrupt signals at three interrupt
ports I.sub.1, I.sub.2 and I.sub.3. The signal applied to the interrupt
port I.sub.3 is generated by an external interrogating device 66 which is
used to interrogate the contents of the PROM's 56. When the interrupt
I.sub.3 is activated, the microprocessor "dumps" the contents of the
PROM's into the interrogating device 66 via an I/O port 68.
The interrogating device may, for example, include a printer which is
capable of producing a printout or "hard copy" of the milage histogram of
the motor vehicle.
FIGS. 3-5 are flowcharts of firmware or software which may be used with the
microprocessor 34 to carry out the functions necessary to determine and
store the number of trips travelled by the motor vehicle in each milage
category.
When the ignition switch 38 is first turned on, the inverter amplifier 42
applies a signal to the interrupt input I.sub.1 of the microprocessor 34.
This interrupt forces the microprocessor to execute a specific routine
called "Permanent Counter Initialization" (PCI) illustrated in FIGS. 3A
and 3B. The purpose of this routine is to scan through all the PROM's and
perform a weighted sum of all the "1" bits to determine the total miles
travelled by the vehicle (odometer function). After thirty seconds, the
timer 44 "times out" and supplies a "load" pulse to the permanent counter
30. At this time, the total miles travelled, as computed by the PCI, are
loaded into the permanent counter 30 via the I/O port 46. Thereafter, the
permanent counter is incremented as the vehicle travels each mile by
pulses produced on line 26.
The pulses produced on line 26 (one count per mile) are also applied to a
second interrupt input I.sub.2 of the microprocessor 34. This interrupt
forces the microprocessor to execute a routine called "Prepare to Burn a
Bit" (PBB) as shown in FIGS. 4A and 4B. The purpose of this routine is the
following:
Every time the interrupt I.sub.2 occurs, the vehicle will have travelled
one more mile. At this time, the microprocessor reads the contents of the
I/O port 36 to determine the current number of miles travelled since the
ignition switch 38 was turned on. The microprocessor then determines which
PROM is to be addressed; it determines the proper address in that PROM;
and it determines the appropriate bit within the bin which should be
burned if the vehicle were to stop at this time.
The appropriate signals are applied to the control, address and data bus
lines; however, no bit is burned unless the ignition switch is turned off
and, thirty seconds thereafter, the DC-to-DC converter 64 applies a 25
volt pulse to the V.sub.pp inputs of the PROM's 56.
Finally, a signal applied to interrupt I.sub.3 by the interrogating device
66 initiates a routine called "output" shown in FIGS. 5A and 5B. When this
routine is called, the microprocessor reads the contents of the PROM's 56
and supplies this information to the interrogating device 66 via the I/O
port 68.
There has thus been shown and described a novel recording apparatus which
fulfills all the objects and advantages sought therefor. Many changes,
modifications, variations and other uses and applications of the subject
invention will, however, become apparent to those skilled in the art after
considering this specification and the accompanying drawings which
disclose preferred embodiments thereof. All such changes, modifications,
variations and other uses and applications which do not depart from the
spirit and scope of the invention are deemed to be covered by the
invention which is limited only by the claims which follow.
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