JPH05296781A - Electronic travel distance recorder - Google Patents

Abstract

PURPOSE:To restrain an error from occurring by installing an error correction code means to be operated at the time of detecting a bit error in the storage contents of a main memory. CONSTITUTION:A control means 3, receiving a control signal, outputs a series of data for a renewal (writing/erasing) of storage contents (total distance of run) of a main memory 4 consisting of a nonvolatile memory, and then issues a display signal so as to renew the display contents of a display 6. An error correction code means 7 added for detecting and correcting a bit error in the memory 4 outputs data out of the control means 3 to a first check bit generating means 7 at the time of renewing the storage contents of the memory 4, generating a first check bit, and it is stored in an auxiliary memory 72 with a check domain of 100 words X 5 bits in conformity with the memory 4. At the time of reading from the memory 4, the storage contents are outputted to a second check bit generating means 73, and on the basis of the first check bit corresponding to the storage contents of the second check bit and the memory 72, the bit error of the memory 4 is detected and corrected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic odometer, and more particularly to error reduction.

[0002]

2. Description of the Related Art When a conventional electronic odometer is used as, for example, an odometer of a vehicle, it is necessary to keep the past total mileage even if a battery abnormality (voltage drop, disconnection, etc.) occurs. Therefore, a non-volatile memory is used (Japanese Patent Laid-Open No. 57-198810 and 59-1964).
14).

[0003]

When the data of the total traveling distance is held in the non-volatile memory, whether or not it can be surely judged whether or not the erroneous data has been written in the non-volatile memory. There was a problem with reliability. That is, in order to make the above-mentioned discrimination, it is easier to find erroneous data as the amount of written data is larger (since erroneous data is a value far from other correct data). However, in the above-mentioned conventional technique, since the data is written in the unit mileage error,
Even in correct data, there is a large difference between the minimum value and the maximum value (latest value), and it is difficult to find erroneous data.

Therefore, the present applicant writes only the upper digit of the mileage into each address of the non-volatile memory as data, and displays the lower digit by using the address itself, thereby writing into the non-volatile memory. In principle, the number of types of data at each address is reduced and the number of times is reduced. Therefore, a technique has been provided which can improve the reliability of facilitating the detection of erroneous data having a distant value (Japanese Patent Laid-Open No. 62-62160). -20131
No. 2).

It is an object of the present invention to provide an electronic odometer that is resistant to bit errors and has higher reliability by adding a new function to the prior art of the present applicant.

[0006]

The present invention focuses on the above-mentioned problems and counts the signals from the distance detecting means to determine the upper digits of the traveling distance after the unit traveling distance and to store the high-order digits of the main memory in a non-volatile memory. Write and hold as data in the address,
In the electronic odometer, which uses the address itself of the main memory for the lower digit of the mileage, shifts to the next address after the unit mileage, and writes and holds the data, There is provided error correction code means for generating a check bit for detecting a bit error of the stored contents according to the data written in the memory and correcting when the bit error is detected.

[0007]

[Operation] Even if a bit error occurs in the stored contents of the main memory,
Since it can be detected and corrected, the error can be suppressed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the embodiments of the accompanying drawings.

FIG. 1 shows a block diagram in which the electronic odometer according to the present invention is used as an odometer of a vehicle. The distance detecting means 1 is provided on a wheel or an axle of the vehicle, and a pulse signal is output for each rotation speed. Is output and is used as the distance input of the distance calculation means 2.

The distance calculation means 2 receives the distance input, counts the number of pulses, and outputs a control signal to the control means 3 for each predetermined unit traveling distance (1 km).

The control means 3 receives the control signal and receives EEPRO.
Data for updating (writing / erasing) the stored contents of the main memory 4 composed of a non-volatile memory such as M is output, and a display signal for updating the displayed contents of the display 6 via the driver 5. Is output.

A method of writing to the main memory 4 and outputting a display signal to the display 6 will be described with reference to the allocation table shown in FIG.

The main memory 4 stores the upper digits of the total mileage at addresses 00 to 99 (for example, the upper 4 digits in the case of 6 digits, that is, 4 bits per digit for a total of 16 bits) at each address 00.
.About.99 data of one kind or two kinds (in this embodiment, "1
・ 2,3,3 "and" 1, 2, 3, 4 ") are written every 100 km, and the control means 3 outputs a display signal to the driver 5 based on this data. The display 6 displays the latest value, and the writing and display signal output methods up to this point are based on the same concept as the above-mentioned prior art of the applicant.

In FIG. 2, when the control means 3 determines that the latest value is the stored content of the address 56 by the above-mentioned predetermined processing, the control means 3 determines the data "1.2" of the address 56.
・ 3.4 "is read out and the total running physician" 123456 km "is obtained based on this data and the address 56.

A feature of the present invention is that an error correction code means 7 is added for detecting and correcting a bit error in the main memory 4. That is, when the stored contents of the main memory 4 are updated, the data from the control means 3 is output to the first check bit generation means 71 to generate the first check bits, and 100 words corresponding to the main memory 4 are generated. -Stored in the auxiliary memory 72 having a check bit area of 5 * 5 bits. When the main memory 4 is read, the stored contents of the main memory 4 are output to the second check bit generation means 73, and the main memory 4 is read based on the second check bits and the first check bits corresponding to the stored contents of the auxiliary memory 72.
Bit error detection and correction are performed.

Next, the bit error correction of the main memory 4 by the auxiliary memory 72 will be described using the check bit generation principle diagram of FIG.

The 21 bits obtained by adding the information bits b16 to b1 of the main memory 4 and the check bits c4 to c0 of the auxiliary memory 72 are arranged and considered as follows. Generally, cx is placed at the position of 2 ↑ x. Position 21 20 19 18 17 16 15 14 13 Bit b16 b15 b14 b13 b12 c4 b11 b10 b9 Position 12 11 10 9 8 7 6 5 4 bits b8 b7 b6 b5 c3 b4 b3 b2 c2 Position 3 2 1 bit c1 b1 b1 c4 to c0 are c4 = b16 XOR b15 XOR b14 XOR b13 XOR b12 c3 = b11 XOR b10 XOR b9 XOR b8 XOR b7 XOR according to the principle shown in FIG.
b6 XOR b5 c2 = b16 XOR b15 XOR b11 XOR b10 XOR b9 XOR
b8 XOR b4 XOR b3 XOR b2 c1 = b14 XOR b13 XOR b11 XOR b10 XOR b7 XOR
b6 XOR b4 XOR b3 XOR b1 c0 = b16 XOR b14 XOR b12 XOR b11 XOR b9 XOR
b7 XOR b5 XOR b4 XOR b2 XOR b1. Therefore, according to this, when a bit error occurs, its position can be immediately known. For example,
When an error occurs at position 11 or bit b7, the check bits c3, c1 and c0 including the error naturally occur, so that it is understood that the incorrect position is 11 or bit b7. Therefore, it is only necessary to correct the bit b7, and correction, that is, restoration to the original is nothing but inversion. Therefore, the signal that this error has occurred and XOR (exclusive OR) may be taken, and the error correction means 74 This is the reason why the correction circuit (1) takes an exclusive OR. By the way, the number k of inspection bits is k when j = 5 to 11 in relation to the number j of information bits to be inspected.
= 4, j = 12 to 26, k = 5, j = 27 to 57, k = 6, and j = 58 to 120, k = 7.

Here, for example, the address 5 of the main memory 4
Even if a 1-bit error occurs in the bit b1 of 6, it can be detected by the check bits c4 to c0 of the auxiliary memory 72, and this error can be corrected by the error correction means 74 and passed to the control means 3. Therefore, there is no problem that the control means 3 uses the contents stored in the main memory 4.

It should be noted that it is possible to detect that a 2-bit error has occurred by adding one parity bit to the auxiliary memory 72. In this case, since the bit position cannot be specified, only the occurrence of a 2-bit error is reported to the control means 3.
The control means 3 receives the result, estimates the erroneous data from the contents stored in the main memory 4, and corrects it. However, the possibility that a bit error of 2 bits or more will occur is extremely low, and in actual use, detection and correction of a 1-bit error are sufficient.

The first check bit generating means 71 and the second check bit generating means 71
The check bit generating means 73 has the same circuit and can be shared. Further, the processing relating to the detection and correction of the bit error does not necessarily have to be carried out by the logic circuit, and it is also possible to carry out the processing by software using the microcomputer for the control means 3.

[0021]

According to the present invention, the signal from the distance detecting means is counted, and after the unit traveling distance, the upper digit of the traveling distance is written and held as data in each address of the main memory composed of the non-volatile memory, In the electronic odometer, which uses the address itself of the main memory for the lower digit of the mileage, shifts to the next address after the unit mileage, and writes and holds the data, An error correction code means for generating a check bit for detecting a bit error of the stored contents according to the data written in the memory and correcting when the bit error is detected is provided. It is easy to deal with bit errors in the static memory. Further, since the algorithm can be simplified without requiring a complicated determination function, it is possible to provide an inexpensive and highly reliable electronic odometer.

[Brief description of drawings]

FIG. 1 is a block diagram when an embodiment of the present invention is used as a vehicle odometer.

FIG. 2 is an allocation diagram of the nonvolatile memory according to the embodiment.

FIG. 3 is a principle diagram of generation of check bits according to the embodiment.

[Explanation of symbols]

 1 distance detection means 2 distance calculation means 3 control means 4 main memory 5 driver 6 indicator 7 error correction coding means

Claims (1)

[Claims] 1. A signal from a distance detecting means is counted, and after the unit traveling distance, the upper digit of the traveling distance is written and held as data in each address of a main memory composed of a non-volatile memory, and the traveling distance of the traveling distance is calculated. The lower digit is written in the main memory in the electronic odometer which utilizes the address itself of the main memory and shifts to the next address after the unit travel distance and writes and holds the data. An electronic mileage, characterized in that error correction code means is provided for generating a check bit for detecting a bit error in the stored contents in accordance with data, and correcting when the bit error is detected. Total.