JPH0146006B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic mileage display device.

Conventionally, electronic mileage display devices have disadvantages such as when the battery is removed for repair or the power supply circuit is disconnected, all the memory contents of the counter are erased. Until now, there has been no device that has been put into practical use to display mileage.

The present invention has been made in view of the above-mentioned circumstances, and includes a distance sensor that generates a pulse every time a vehicle travels a certain distance, and an ODD lower unit that stores and outputs distance data based on the pulse for displaying the cumulative distance. A RAM for storing data, a RAM for storing TRIP data which can be reset by an operation switch and which stores and outputs distance data based on the pulses for displaying the cumulative distance after the reset, and at least a RAM for storing the ODD lower data mentioned above. Non-volatile memory (hereinafter referred to as "NVRAM") that stores and outputs data based on distance data output from RAM
Then, the above pulses are counted and each of the above is used as distance data.
A distance data controller that writes distance data into RAM, reads distance data from each of the above RAMs as necessary, and writes data based on the same distance data into the above NVRAM, and displays distance based on the distance data stored in each of the above RAMs and NVRAM. The memory area of the NVRAM is
It has three upper groups, first, second, and third,
The first group and the second group each constitute a binary counter, and the third group is further divided into a plurality of storage units of 1 byte, and the distance data controller
Every time the distance data stored in the RAM for storing ODD lower-order data reaches a predetermined value, the +1 count-up data is simultaneously written to all bits of one of the above-mentioned storage units, and the above-mentioned ODD lower-order data is stored. Each time writing is completed for all memory units in the third group, data incremented by 1 is alternately written into the second group and the first group, and the data is incremented by one. The memory contents of the third group are reset, and the memory contents of the last written group among the second group and the first group, the memory contents of the third group, and the lower ODD For data storage
It is an object of the present invention to provide an electronic mileage display device configured to read the contents of RAM and output it to the display device.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a circuit configuration diagram showing an embodiment of the present invention, in which 1 is a mileage sensor attached to the transmission output shaft of a vehicle, 2 is a TRIP reset switch, and 3 is a switch between TRIP and integration. ODD/TRIP switch that performs
4 is a microcomputer (microcomputer); 5 and 6 are memory circuits (hereinafter referred to as RAM) that store the results of counting pulses from the distance sensor 1 by the distance data controller 7; This is RAM for data storage. Reference numeral 8 denotes an NVRAM, into which data output from the RAMs 5 and 6 is written or read by a distance data controller 7, which is a control circuit. 9 is a power supply circuit, 10 is an ignition key switch, 11 is a battery, 12a,
12b and 12c are waveform shaping circuits, respectively.
Further, 13 is a display section, ODD display section 14,
It consists of a TRIP display section 15, a Km display section 16, and an m display section 17. Km display section 16 and m display section 1 above
7 is configured to be displayed in seven segments, and a predetermined display is made on the display section 13 from the distance data controller 7 via the display controller 18 and display driver 19. Note that the Km display 16 is made larger than the m display section 17 to make it easier to distinguish.

Next, the operation of the circuit diagram described above will be explained.

First, when the vehicle travels, the pulse from the distance sensor 1 is counted as the distance traveled by the distance data controller 7, and the total distance traveled is calculated.
The RAM 5 of the ODD counter circuit and the section mileage are stored in the RAM 6 of the TRIP counter circuit.

The distance data controller 7 counts the distance traveled, and the stored content is a constant value (for example, 999
When the distance reaches approximately 800m (a fixed value between 1m and 1m), the memory contents of RAM5 are reset,
Count up NVRAM8 by +1.

In addition, the memory contents of NVRAM 8, RAM 5, and 6 are always transmitted to the display controller 18 by the distance data controller 7, and when the ODD/TRIP switch 3 is ON, the data of NVRAM 8 and the data of RAM 5 are added together. , display section 13
At the same time, the ODD display section 14 also lights up.

On the other hand, when the ODD/TRIP switch 3 is OFF, the data in the RAM 6 of the TRIP counter circuit is displayed on the display section 13.
The TRIP display section 15 also lights up.

Here, the TRIP reset switch 2 resets the memory contents of the RAM 6 by turning on the switch, so that it is possible to newly store the section mileage.

Also, ignition key switch 10
When turned off, NVRAM8, display driver 19,
Although the power supply to the waveform shaping circuits 12a, 12b, 12c, etc. is stopped, the microcomputer 4, which is composed of the RAMs 5, 6, etc., is constantly supplied with the power supply B, so that its stored contents are retained.

However, if the power is cut off at the terminal, such as when the battery 11 is removed, the memory contents of RAM5 and 6 will be erased, but since the NVRAM8 is a non-volatile memory circuit, its contents will be retained even if the power is not supplied. Memory contents are always retained without being erased.

Next, the calculation method of the NVRAM 8 will be explained in detail with reference to FIGS. 2 and 3. Figure 2 is a layout diagram of the above NVRAM8.
The memory area is divided into three upper memories A, B, and C as shown in the figure.

Memory C is divided into 1 byte (8 bits) as one storage unit, and every time the storage contents of RAM 5 reach a certain value (for example, 800 m), all bits are cleared from memory R ₁ as shown in Figure 3. Filled with 1.

When memory _R20 is filled, the memory contents of memory A or B are counted up by +1, and memories _R1 to _R20 are reset. Memories A and B constitute a quaternary counter, and each time memory C overflows, the stored contents of memories _R1 to _R3 are counted up by +1.

By writing to NVRAM8 in this way, the number of writes to one storage unit in memory C is reduced to
It is the value obtained by dividing the number of times the memory contents of RAM reach a predetermined value by the number of memory units in the memory (20),
The number of writes to memory A and the number of writes to memory B are half of the number of times writes to all memory units in memory C have been completed, that is, in this embodiment, the memory content of the ODD lower data storage RAM is This is 1/40th of the number of times the predetermined value is reached.

When reading, the memory _R1 of the memory that was last counted up (for example, memory A)
~R Takes a majority vote on the stored contents of ₃ , and outputs data that is the same at least two times. If all the data are different, use another set of memory B.
A majority vote is taken for the stored contents of R ₁ to _{R 3} in the same manner as described above, and the data with more data is output.

Here, memories A and B store data in binary notation, so if the stored content changes even by 1 bit, the data changes significantly, so memories R ₁ ~
By storing the same data in three _R3s and performing majority voting, data destruction due to 1-bit errors is prevented. Furthermore, since the memory C stores one content in units of one byte, even if the 1-bit storage content changes, if a majority vote of "1" and "0" is taken, data destruction can be prevented.

As is clear from the above description, according to the electronic mileage display device according to the present invention, when the battery of the vehicle is removed for repair, the power supply circuit is disconnected, and the memory contents of the RAM are will be destroyed. However, even in this case, the mileage is 0.8
Since it is n times Km and is stored in the non-volatile memory NVRAM, its value will never disappear.

However, only the data stored in the memory part stored in the RAM will be erased, but in the present invention, the data of 799m will only be erased as the maximum value, which is from the perspective of the car's mileage display. The error is extremely small and poses no practical problem, and the vehicle's mileage can be displayed with high accuracy.

The present invention is characterized by being able to display distances of less than 1.0 km, and by making it possible to display and memorize distances of less than 1.0 km, accuracy can be improved at the stage of re-displaying after turning off the power. can be achieved.

In addition, in order to increase the accuracy, it is possible to display and memorize less than Km in small steps, for example every 0.1 Km, but there are also problems such as memory capacity, and if the amount of writing becomes large, it may become impossible to write and some parts of the memory may be lost. Problems such as the following may occur, so in practice, as shown in the present invention, one unit is 0.8 km as an example.

Further, according to the present invention, there is provided a first, second, and third group of NVRAM memory areas, and a third group of NVRAM memory areas is provided.
The group is further divided into 1-byte storage units, and each time the distance data stored in the ODD lower data storage RAM reaches a predetermined value, all bits are sequentially stored in one of the above storage units. Data with all 1s is written, and each time writing of all memory units of the third group is completed, the data of the first group is written.
Since data incremented by +1 is written alternately to the above group and the above second group, the memory contents of the above third group are reset.
The number of writes to one storage unit is
The number of times the distance data stored in the ODD lower data storage RAM reaches a predetermined value is divided by the total number of storage units, and the number of writes to the second group and the number of writes to the first group are , is the value obtained by halving the number of times writing to all storage units of the third group is completed.
The number of times of writing in any of the above cases is significantly smaller than the number of times of writing of the least significant digit in a conventional method in which the least significant digit of the counter is simply rewritten and added by +1. The lifespan of non-volatile memory is determined by the number of writes, so by writing as described above, NVRAM
The lifespan of can be significantly extended.

Also, even if abnormal data is written for some reason while writing to memory C,
By using the last data before all the data stored in the memory C is written, at worst, only a distance error corresponding to +1 count up with respect to the memory C will occur, and the memory A or the memory Even if abnormal data is written in the same way while writing to B,
Every time writing to all memory units of the memory C is completed, writing to the memory A and memory B is performed alternately, so abnormal data corresponds to +1 count up for the memory A or memory B. The only difference is the distance error.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram of an embodiment according to the present invention, and FIG. 2 is a diagram of a nonvolatile memory according to an embodiment according to the present invention.
The layout diagram in NVRAM, Figure 3 is the same as Figure 2.
FIG. 2 is an explanatory diagram of operations in NVRAM. 1... Distance sensor, 2... TRIP reset switch, 3... ODD/TRIP changeover switch, 4...
Microcomputer, 5...RAM for storing ODD lower data,
6...RAM for storing TRIP data, 7...Distance data controller, 8...NVRAM, 9...Power circuit, 10...Ignition key switch,
11...Battery, 12a, 12b, 12c...
Waveform shaping circuit, 13...display section, 14...ODD
Display unit, 15...TRIP display unit, 16...Km display unit, 17...m display unit, 18...display controller, 19...display driver.

Claims (1)

[Claims] 1. A distance sensor that generates a pulse every time the vehicle travels a certain distance, a RAM for storing ODD lower data that stores and outputs distance data based on the pulse for displaying the cumulative distance, and that can be reset using an operating switch. TRIP data storage RAM that stores and outputs distance data based on the pulses for displaying the cumulative distance after the same reset; and at least a TRIP data storage RAM that stores and outputs data based on the distance data output from the ODD lower data storage RAM. A nonvolatile memory to output, and a distance data controller that counts the pulses and writes them as distance data in each of the RAMs, reads the distance data from each of the RAMs as necessary, and writes data based on the same distance data to the nonvolatile memory. and each of the above
It has a display device that displays distance based on distance data stored in RAM and nonvolatile memory,
The memory area of the nonvolatile memory has three upper groups, first, second, and third, and the first
and the above second group each have 2
The third group is further divided into a plurality of storage units of 1 byte each, and the distance data controller configures the ODD.
Every time the distance data stored in the lower data storage RAM reaches a predetermined value, data incremented by +1 is simultaneously written into all bits of one of the above storage units at the same time.
The memory contents of the ODD lower data storage RAM are reset, and each time writing is completed for all memory units of the third group, the data counted up by +1 is alternately added to the second group and the first group. At the same time, the memory contents of the third group are reset, and the memory contents of the last written group among the second group and the first group and the memory contents of the third group are written. and RAM for storing the above ODD lower data
An electronic mileage display device, characterized in that the electronic mileage display device is configured to read out and output the stored contents to the display device.