JPH03285112A - Electronic odometer - Google Patents

Abstract

PURPOSE:To prevent the integral running distance data and a storing address which stores the running distance data from being broken when electricity is supplied by writing and correcting the integral running distance data at a shorter running distance than usual when an error is brought about. CONSTITUTION:A counter 8 counts pulses of a running distance sensor which are output every time a vehicle runs a predetermined distance, with generating a first signal S1 every time the running distance becomes a first predetermined value. Moreover, the counter 8 generates a second signal S2 every time the running distance reaches a second predetermined value shorter than the first predetermined value. When an error checking circuit 7 detects an error, a latch circuit 9 temporarily stores the content, namely, the changing address and correcting data of the integral running distance. Every time the first signal S1 is input, normally, the integral running distance data of a presettable counter 2 is stored in an involatile memory 6. Meanwhile, at the occurrence of an error, the address of the involatile memory 6 is updated in accordance with the content of the latch circuit 9 when the second signal S2 is input, and the correcting data of the integral running distance is written into the updated address.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a vehicle-mounted electronic odometer using a nonvolatile memory.

[Prior art]

As a conventional electronic odometer, there is one as shown in FIG. 3 (for example, as described in Japanese Patent Laid-Open No. 56-89009).

In FIG. 3, a signal S0 is a signal from a travel distance sensor (not shown), and is, for example, a pulse signal output every time the vehicle travels about 1 m.

Further, counter 1 receives the above signal S. For example, 1
Every time 000 pulses are counted (the vehicle runs 11a1), the signal S signal is output.

Further, the presettable counter 2 counts the signal S□ by adding it to the preset previous cumulative travel distance. Then, the value of the counting result, that is, the cumulative travel distance of the vehicle is displayed on the display 4 via the decoder driver circuit 3.

In addition, the nonvolatile memory (for example, EEFROM, etc.) 6 is
Every time the above-mentioned signal S is given, the count value of the presettable counter 2 at that time, that is, the cumulative travel distance is stored.

Further, the voltage monitor 5 detects power-on since the value of the power supply voltage va rises to a predetermined value or more. When power-on is detected, the nonvolatile memory 6 refers to the address where the accumulated mileage data is stored, reads the accumulated mileage data, and stores the accumulated mileage data in the presettable counter 2. The presettable counter 2 treats the set cumulative travel distance as an initial value, and sequentially adds the signal S to that value for counting.

Therefore, even if the power is turned off when the engine is stopped, the cumulative mileage data will not be lost. When the power supply voltage rises at the next engine start, the cumulative travel distance stored in the nonvolatile memory is read out and preset in the presettable counter 2.

However, with only the above configuration, a problem occurs when an error occurs, so some devices are provided with an error check circuit 7 (for example, as described in Japanese Patent Application Laid-open No. 105915/1982).
.

That is, the error check circuit 7 uses the nonvolatile memory 6
An error check is carried out when reading the storage data of the cumulative travel distance from the system, and when an error occurs, the storage area of the non-volatile memory 6 is immediately updated, and the correction data of the cumulative travel distance is written to the updated address.

Note that the error checking method in the error check circuit 7 described above is to write the same mileage data in three locations, taking into account the reliability of the written data after being written into the nonvolatile memory, and When reading out the data, there is a method of reading out the mileage data stored in three locations and comparing them with each other to detect an error using majority vote (for example, as described in Japanese Patent Laid-Open No. 107207/1982).

[Problem to be solved by the invention]

However, in the conventional electronic odometer as described above, if an error occurs in the read data,
Problems may arise when storing corrected values and update addresses for mileage data in non-volatile memory.

In the operation of the electronic odometer as described above, first,
The accumulated mileage data of the presettable counter 2 is written into the non-volatile memory 6 at the timing of the signal S8 generated every time a certain distance is traveled, and after the writing is completed, it is read out and an error check is performed by the error check circuit 7, and the address is updated when an error occurs. However, in the sequence of writing correction data for cumulative mileage to the update address, signal Sl is generated when the vehicle is normally running, the engine is operating normally, and the power supply voltage is low. Since it is considered normal, no problem arises.

However, when the power is turned on, that is, when the engine is started, the battery voltage drops significantly due to engine cranking. After an error is detected, when writing the updated address and correction data for the cumulative mileage into the non-volatile memory 6, as shown in Figure 4, there is a possibility that the power supply voltage has dropped significantly due to cranking. In such a case, the corrected data of the changed address and cumulative mileage cannot be stored correctly, causing a problem that the odometer function will stop after that.

In addition, in order to deal with the above problem, even if we apply the power-on clear method that clears when the power supply voltage exceeds a predetermined value, power-on clear operates even if the voltage rises momentarily and immediately drops. However, non-volatile memory 6
Since the writing time of 10 seconds is required, it may not be possible to handle this. As a result, it is necessary to use a backup power source and the like, which causes a problem in that the size of one circuit configuration increases, leading to an increase in cost.

In addition, in order to solve the above-mentioned problem, for errors that occur during error checking when the power is turned on, correction data is set in the presettable counter 2 and displayed, but the error correction value is not stored. A method of correcting when the primary constant travel distance signal S1 is generated is also conceivable. However, when this method is used, the first problem occurs.

In other words, considering the error checking method based on majority voting, when data is corrected using data from three locations A, B, and C for mileage data, it is assumed that there is an error in memory location A when the power is turned on. Then, there will be no modification at this point.

When the next fixed mileage signal S1 occurs, the mileage data obtained by adding a fixed distance value to the memory areas of the error occurrence locations A, B, and C is accessed again, and after executing an error check, the error occurrence memory location A is accessed again. The operation to switch is entered here. At this time, since an error does not necessarily occur in the storage area of A, accesses will be executed several times. During this time, it cannot be determined that errors will not occur in other storage areas B and C. If it is assumed that an error has occurred in storage area B, the error in storage area A will become undetectable, and from now on, the error will occur at the storage area A.
Area B is determined to be correct, and the correct storage area C
is determined to be an error, so the storage area C is constantly switched, making it impossible to perform correct error checking. Furthermore, since the storage area is constantly switched, the storage area is reduced, which ultimately leads to a system failure in a short period of time.

The present invention has been made in order to solve the problems of the prior art as described above, and it is an object of the present invention to provide an electronic odometer that is free from memory corruption of cumulative mileage data and mileage data storage address when the power is turned on. With the goal.

[Means for Solving the Problems] In order to solve the above problems, the present invention is configured as described in the claims.

That is, in the present invention, the pulses of a travel distance sensor that generates a pulse every time the vehicle travels a certain distance (for example, about 1 m) are counted, and each time the travel distance reaches a first predetermined value (for example, 1 km), the pulses are counted. transmitting a first signal;
A counter that sends out a second signal every time it reaches a second predetermined value (for example, room) that is shorter than a predetermined value of A latch circuit for temporarily storing correction data is provided. 1 During normal times, the accumulated mileage data of the presettable counter is stored in a nonvolatile memory every time the first signal is applied, and when an error occurs,
When the second signal is applied, the address of the nonvolatile memory is updated according to the contents of the latch circuit, and the correction data of the cumulative mileage is written to the updated address.

With the above configuration, in the present invention,
After the vehicle starts running, that is, after the engine has completely started and the power supply voltage has become normal, the change address and cumulative mileage data at the time of error are corrected.
There is no possibility of being affected by power supply voltage drop due to cranking.

Further, since the correction is performed when the vehicle has traveled a second predetermined distance shorter than the first predetermined distance for normal writing, the corrected value is written during normal writing.

[Embodiments of the invention]

FIG. 1 is a block diagram of one embodiment of the present invention.

In FIG. 1, a signal S0 is a signal from a travel distance sensor (not shown), and is a pulse signal that is output, for example, every time the vehicle travels 1 meter.

Further, the counter 8 counts the above-mentioned signal Sa, and sends a signal S every time the travel distance reaches a first predetermined value (for example, 1), and a second A signal S2 is sent each time the signal reaches a predetermined value (for example, Loom).

Further, the presettable counter 2 counts the signal S□ by adding it to the preset previous cumulative travel distance. And the value of the counting result.

In other words, the cumulative mileage of the vehicle is determined by the decoder driver circuit 3.
It is displayed on the display 4 via the.

Furthermore, each time the above signal Si is applied, the nonvolatile memory 6 stores the count value of the presettable counter 2 at that time,
That is, the cumulative travel distance is stored.

Further, the voltage monitor 5 detects power-on since the value of the power supply voltage v0 rises to a predetermined value or more.

When power-on is detected, the nonvolatile memory 6 refers to the address where the cumulative mileage data is stored and reads the cumulative mileage data.

The cumulative mileage data is set in the presettable counter 2 via the error check circuit 7.

The error check circuit 7 performs an error check when reading the stored data of the cumulative travel distance from the nonvolatile memory 6.

Further, when the error check circuit 7 detects an error, the latch circuit 9 temporarily stores the contents of the error, that is, the changed address and the correction data of the cumulative mileage.

Next, the action will be explained.

First, when the power is turned on, the voltage monitor 5 detects that the power is turned on, reads cumulative mileage data from the non-volatile memory 6, and sets the cumulative mileage data in the presettable counter 2 via the error check circuit 7 when normal. . Note that processing when an error occurs will be described later.

During normal driving, a certain distance (for example, 1-
) Every time the vehicle travels, the counter 8 sends out a signal S1, and the presettable counter 2 sequentially counts the signal S by adding it to the previously set cumulative travel distance. Then, the counted value, that is, the cumulative travel distance, is displayed on the display 4 via the decoder driver circuit 3.

Further, the count value of the presettable counter 2 is written into the nonvolatile memory 6 every time the signal S is applied.

On the other hand, when the above writing is performed, the error check circuit 7 reads the mileage storage data from the nonvolatile memory 6 and checks whether it has been correctly stored. As a result, if the memory is correctly stored, the normal operation described above continues; however, if an error is detected, the storage area of the non-volatile memory 6 is updated, and the updated address and cumulative mileage are corrected. Set the data in the latch circuit 9. When a signal S2 (for example, output every 100 m) is applied from the counter 8, the correction data of the cumulative travel distance is stored in the update address of the nonvolatile memory 6.

Also, when reading the cumulative mileage data from the nonvolatile memory 6 when the power is turned on.

If the error check circuit 7 detects an error, the correction value and update address of the cumulative mileage data are latched into the latch circuit 9. Then, when the signal S2 is applied in the same manner as described above, the correction data of the cumulative mileage is stored in the above update address.

As mentioned above, in the circuit shown in Fig. 1, when the power is turned on, the cumulative mileage stored in the non-volatile memory 6 is immediately set to the presettable counter 2 and displayed, but the memory contents when an error occurs The update timing is configured to be performed at the time when the signal S2 outputted after the vehicle has traveled a predetermined distance is given. When the vehicle is running, the engine is expected to have started completely and the power supply voltage is expected to be normal, so if the memory contents are updated at this time, there is no risk of any inconvenience occurring.

FIG. 2 is a diagram showing the power supply voltage waveform and write timing in the above operation. As shown in FIG. 2, the signal S2 is applied after the vehicle starts running, and at this point the power supply voltage is stable at a normal value.

Further, in the embodiment shown in FIG. 1, when an error occurs, the update address and the corrected value of the cumulative mileage are temporarily stored in the latch circuit 9.
There is no risk of making a mistake in correction when an error occurs.

Note that the voltage monitor 5 determines that the power is turned on every time the power supply voltage v0 rises above a predetermined value, so as shown in FIG. When the device starts up again, it is determined that the power has been turned on, and reading from the nonvolatile memory 6 and error detection by the error check circuit 7 are performed again. Therefore, after the first error detection, the power supply voltage decreases rapidly due to cranking, which causes the latch circuit 9
Even if there is a case where the corrected information cannot be stored, the error check and corrected information will be reliably performed the next time the power supply voltage is turned on.

Further, since the correction is performed when the vehicle has traveled a second predetermined distance shorter than the first predetermined distance for normal writing, the corrected value is written during normal writing.

〔Effect of the invention〕

As explained above, according to the present invention, when an error occurs, correction writing of cumulative mileage data is performed.
By configuring it to be performed when the vehicle has traveled a predetermined distance that is shorter than the distance traveled for normal writing,
There is no risk that the storage of cumulative mileage data and mileage data storage address will be destroyed due to a voltage drop at power-on caused by cranking when starting the engine, etc., and the reliability of the odometer can be improved. Moreover, compared to providing a backup power source, the configuration is simpler and more reliable control can be performed.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a diagram showing write timing in the present invention, Fig. 3 is a block diagram of an example of a conventional device, and Fig. 4 is a diagram showing write timing in the conventional device. It is a diagram. <Explanation of symbols> 1... Counter 2... Presettable counter 3... Decoder driver circuit 4... Display 5... Voltage monitor 6... Non-volatile memory 7... Error check circuit 8 ...Counter 9...Latch circuit

Claims (1)

[Scope of Claims] A mileage sensor that generates a pulse every time the vehicle travels a certain distance; and a mileage sensor that counts the pulses and sends out a first signal every time the mileage reaches a first predetermined value; A counter that sends a second signal every time it reaches a second predetermined value that is shorter than the first predetermined value, and a preset value of the previous cumulative mileage read from the non-volatile memory below when the power is turned on. a presettable counter that counts the first signal of the counter by adding to the first signal of the counter; a display that displays the distance traveled according to the counting result of the presettable counter; and a display that stores the address of the data storage area and when writing data. a non-volatile memory that refers to the address and stores the counting result of the presettable counter at that address; an error check circuit that performs an error check on the stored data when reading data stored in the non-volatile memory; a latch circuit that temporarily stores an updated address and cumulative mileage correction data when the circuit detects an error; It stores the count value of the presettable counter, and if an error occurs, stores correction data at the update address based on the stored contents of the latch circuit at the time when the second signal of the counter is applied. An electronic odometer characterized by: