JPH0373958B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method of storing data in an EEPROM, which is a nonvolatile memory that can be electrically erased, written to, and read from, and particularly relates to a method of storing count data.

[Prior art]

In recent years, the development of such EEPROMs has progressed, and some devices that can be controlled with a single 5V power supply, which is the same as controlling peripheral devices, have appeared, making it possible to use them over a wide range of applications, especially without the need for a dedicated backup power supply, which was often difficult in the past. There are great expectations for its use as a solution to data storage problems in small systems.

However, when used similarly to RAM, rather than as a temporary backup during power outages,
Unlike normal RAM, EEPROM has two stages of writing (rewriting): erasing and writing, and is 10m long.
Since it takes a relatively long time of about 20 seconds, there are measures to be taken in case of interruption during that time, i.e., to determine whether the data read after restarting the operation is the correct final data rather than the meaningless data that was interrupted, or It is necessary to ensure that complete data immediately before interruption is obtained, and for example, methods have been proposed in which multiple storage areas are provided for one type of data and the final data is determined by majority vote.

Another point that must be solved if EEPROM is to be used in the same way as RAM is:
There is a problem with the limit on the number of writes. That is, currently
EEPROM can be erased and written to approximately ¹⁰⁶ times. Therefore, when using this as a counter, if a specific area is provided and the numbers are simply counted there, it will only be possible to count up to the number of erasing/writing possible.

[Summary of the invention]

The present invention was made in view of these circumstances, and its purpose is to always obtain reliable final data regardless of interruptions in writing operations, and to exceed the limit on the number of erasing and writing times for individual areas. The object of the present invention is to provide a method for storing counting data in an EEPROM that allows counting of numbers.

In order to achieve such an objective, the present invention
The maximum number of counting digits is divided into multiple categories in order of digits, and for the upper category, a counting data storage area is provided for each category, and for the lowest category, a counting data storage area is provided for the number of items smaller than the maximum count value of the relevant category, When updating the count value, search the contents of the count data storage area of the lowest division for the last data just before the natural number sequence is disturbed, and
The updated value is stored in the area of the next rank, and when the updated value becomes "0", the contents of the higher classification are further updated.

Generally, as a way to ensure final data,
For each type of data to be stored, n data storage areas of 3 or more and corresponding sign storage areas are provided, and the sign storage areas contain n+1 or more different signs whose ranks can be specified, for example, consecutively. When updating data, the last consecutive sign of the sign is searched as corresponding to the final data, and the data of the next rank in the corresponding data storage area is stored. A possible method is to store the updated data in the storage area and then rewrite the signature in the corresponding signature storage area to a sign ranked one rank after the last ranked signature. In other words, the signature is rewritten once the new data has been written,
This signature makes it possible to detect the latest and final data among complete data, but using this method for storing count data has the problem of the limit on the number of writes mentioned above. In the case of count data, since the data itself is a continuous natural number, it can also be used as a sign as it is.

Therefore, the present invention divides the maximum number of digits,
For the lowest category, by providing a large number of data storage areas ([maximum count value of the category - 1] or less), the number of rewrites per area can be reduced, and the final This allows data to be detected. For upper divisions, as described above, it is possible to provide three or more data storage areas and signature storage areas for each division, or other methods, such as the majority voting method described above, can be used to determine the final data. Just do it like this. Hereinafter, the present invention will be explained in detail using Examples.

〔Example〕

FIG. 1 is a block diagram of a system showing an embodiment of the present invention applied to an electronic odometer. In the figure, numeral 10 denotes a processor, specifically constituted by, for example, a well-known microprocessor.
20 is a RAM, and 30 is an EEPROM. Also 4
0 is a sensor which sends a pulse signal PS generated every fixed distance traveled to the processor 10 via the input interface 50. Furthermore, 60 is a display for displaying the distance traveled, and 70 is a driving circuit thereof, which is controlled by the processor 10.
The EEPROM 30 is provided with a program area 31 used as a fixed memory and a data area 32 used like a RAM. D1 is a data signal exchanged between the processor 10 and the data area 32, D2 is a data signal read from the program area 31, A1 is an address signal specifying a specific address area of the data area or program area. R1 is a read control signal, and W1 is a write control signal.

In the above configuration, the program area 31 is
For example, fixed data is stored in advance, such as the number of pulses input from the sensor 40 per 100 m calculated by assuming standard diameter tire circumference (m)/number of pulses per tire rotation = A, and n ₀ = 100/A. The data area 32 is used to store counting data for counting the number of pulses. Note that 80 is a circuit for preventing the rewriting of data that should not be rewritten carelessly, such as the above-mentioned fixed data, and is a NAND circuit provided that no signal is sent to a specific address signal line.
AND circuit installed on the write control signal line, provided that all inputs of NAND ₁ are inactive.
By opening _AND1 , it is possible to prevent the content of the address from being rewritten so that the digit corresponding to the specific address signal line becomes "1". Further, 90 is a circuit for preventing erroneous data from being written when the processor 10 goes out of control.During normal operation of the processor 10, the circuit is repeatedly discharged by the clock pulses sent from the processor, and its terminal voltage is reduced. The comparator detects that the terminal voltage of the capacitor _C1 , which is suppressed below a certain level, exceeds the reference voltage B, which is higher than the above certain level, and in that case, the comparator
When the output of COM ₁ becomes "0", the AND circuit AND ₁ is closed and writing is prohibited.

Therefore, the capacity of EEPROM30 is 512 bytes,
Assuming the maximum number of digits to be counted as 4 bytes = 32 bits,
The area of the EEPROM 30 is divided into two as shown in Figure 2, and one side has a count data storage area R ₁ for the lowest byte.

Claims (1)

[Scope of Claims] 1. The maximum number of counted digits is divided into a plurality of divisions in digit order, and a counting data storage area is provided for each division for the upper division, and the maximum count value for the lowest division is smaller than the maximum count value of the lowest division. A count data storage area for the number of pieces is provided, and the count value is updated by searching the content of the count data storage area for the lowest division as the final data immediately before the natural number sequence is disturbed.
This shall be done by storing the updated value in the counting data storage area of the next rank after the concerned counting data storage area, and if the updated value becomes "0", further updating the contents of the counting data storage area of the higher category. A counting data storage method in EEPROM characterized by: 2. An overflow area is provided to identify whether the carry has been carried out correctly, and when the final data retrieved for the lowest division is "0", the lowest digit in the upper division is stored before storing the updated value. When compared with the contents of the overflow area, if they do not match, the count value of the upper division is updated, and on the other hand, if the updated value of the lowest division is "0", the contents of the data storage area of the upper division are updated. 2. A method for storing count data in an EEPROM according to claim 1, characterized in that the updated value of the least significant digit in the upper classification is stored in an overflow area in advance.