JPH0765592A - Nonvolatile memory - Google Patents

Abstract

PURPOSE:To prolong lifetime without lowering a throughput of a system and to enable execution of notification as to whether the lifetime of a memory cell expires or not. CONSTITUTION:A comparator circuit 21 reads out data from a memory cell array 20 in response to input of a write enable signal, compares the data with data from outside and notifies the result to an AND circuit 22. The AND circuit 22 checks input of the write enable signal to the memory cell array 20 when the result of comparison shows coincidence, while it permits the input of the write enable signal to the memory cell array 20 when the result shows coincidence. A counter circuit 23 executes increment when the input of the write enable signal to the memory cell array 20 is permitted, and compares a count value after the increment with the maximum number of rewritable times held inside beforehand. When the count value exceeds the maximum number of rewritable times, the counter circuit 23 outputs an alarm signal.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a non-volatile memory,
In particular, it relates to an electrically erasable and electrically writable nonvolatile memory such as an EEPROM or a flash memory.

[0002]

2. Description of the Related Art Conventionally, this type of nonvolatile memory has been electrically erasable and writable, but there is a limit (upper limit) to the number of rewritable times. If rewriting is performed over the number of times that rewriting is possible, the non-volatile memory deteriorates and the write data cannot be guaranteed. In that case, it is not known when the non-volatile memory reaches its end of life.

Therefore, a method is conceivable in which the number of times writing is performed in the non-volatile memory is counted by hardware such as a counter provided outside the non-volatile memory or software of a microcomputer, and the counted value is displayed. ing. Such a method is disclosed in JP-A-62-527.
There are techniques disclosed in Japanese Patent Laid-Open No. 96-96, and Japanese Patent Laid-Open No. 63-200399.

Further, in the non-volatile memory, the contents of the memory cell are rewritten by the data from the outside without judging whether the data written from the outside is the same as the already recorded data.

Therefore, even if the data to be newly written from the outside is the same as the already-recorded data, the memory cell is rewritten. Therefore, in a nonvolatile memory with a limited number of rewritable times, The limit of rewritable times will be reached soon.

In order to solve this problem, it is judged by the software of the microcomputer whether the data newly written from the outside is the same as the already recorded data,
A method of extending the life of the non-volatile memory by stopping the writing of the data to the non-volatile memory if the same data is also considered. Regarding such a technology, Japanese Patent Laid-Open No.
There is a technique disclosed in Japanese Patent Laid-Open No. 4-66525.

[0007]

In the conventional non-volatile memory described above, the number of times writing is performed is counted by external hardware or software of a microcomputer, and the counted value is displayed. There is a problem that extra hardware and software are required to monitor and count the rewriting of data in the memory from the outside, which leads to an increase in the amount of hardware and a decrease in system throughput.

Further, since the writing of the same data when rewriting the memory cell is prevented by the software of the microcomputer, in the writing process in the software, after the data of the address to be written is read once, Compare the data with the write data,
It is necessary to add a process for determining whether they are the same. Therefore, there is a problem that the throughput of the system using this memory circuit is reduced.

Therefore, an object of the present invention is to solve the above problems and provide a non-volatile memory capable of knowing the life of a memory cell without increasing the amount of hardware and reducing the throughput of the system. is there.

Another object of the present invention is to provide a non-volatile memory capable of prolonging the life of the system and knowing the life of the memory cell without lowering the throughput of the system.

[0011]

A non-volatile memory according to the present invention is a non-volatile memory having an upper limit on the number of times data is rewritten, and is provided with counting means for counting the number of times data is rewritten.

Another non-volatile memory according to the present invention is a non-volatile memory having an upper limit on the number of times of rewriting data, and a comparing means for comparing rewriting data from the outside with data written inside. A means for controlling the rewriting data from the outside to be written in the inside when a match is detected by the comparing means, and a counting means for counting the number of times the rewriting data from the outside has been written in the inside. I have it.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In the figure, non-volatile memory (EEPR
The OM) 1 includes a memory cell array (CELL) 10 and a counter circuit (COUNTER) 11. The nonvolatile memory 1 is connected to the power supply line Vcc and the ground line GND.

When data is read from the nonvolatile memory 1, the output enable signal (OE), the chip enable signal (CE), and the address signal (ADDRES).
S) is supplied to the memory cell array 10, and the data (DATA) read from the memory cell array 10 is output to the outside.

When data is written in the nonvolatile memory 1, a write enable signal (WE), a chip enable signal (CE) and an address signal (ADDRESS).
Are supplied to the memory cell array 10, and external data (DATA) is written in the memory cell array 10.

The counter circuit 11 is a memory cell array 10
The count value is incremented by a write enable signal to, and the count value after the increment is compared with the maximum rewritable number held in advance. When the counter circuit 11 detects that the count value exceeds the maximum rewritable count by the comparison, the alarm signal (ALAR
M) is output to the outside.

FIG. 2 is a block diagram showing the configuration of another embodiment of the present invention. In the figure, non-volatile memory (EEP
The ROM 2 includes a memory cell array (CELL) 20, a comparison circuit (COMPARATOR) 21, and an AND circuit 2.
2 and a counter circuit (COUNTER) 23. The nonvolatile memory 2 is connected to the power supply line Vcc and the ground line GND.

When data is read from the nonvolatile memory 2, an output enable signal (OE), a chip enable signal (CE), and an address signal (ADDRES).
S) is supplied to the memory cell array 20, and the data (DATA) read from the memory cell array 20 is output to the outside.

When data is written in the nonvolatile memory 2, the chip enable signal (CE) and the address signal (ADDRESS) are supplied to the memory cell array 20, and the write enable signal (WE) is supplied to the comparison circuit 21. And the AND circuit 22.

The comparison circuit 21 reads data from the memory cell array 20 in response to the input of the write enable signal, and also reads the read data and external data (D
ATA) and the comparison result is output to the AND circuit 22 as a determination signal.

The AND circuit 22 ANDs the judgment signal of the comparison circuit 21 and the write enable signal, and uses the operation result as a write enable signal for the memory cell array 20.
And output to the counter circuit 23.

That is, the AND circuit 22 is the comparison circuit 21.
When the data mismatches are detected, the write enable signal is passed through and output to the memory cell array 20 and the counter circuit 23 as it is. Therefore, external data is written in the memory cell array 20, and the data is updated.

At this time, the counter circuit 23 counts up according to the write enable signal from the AND circuit 22, and compares the count value after the count-up with the maximum rewritable number held inside beforehand.

When the counter circuit 23 detects that the count value exceeds the maximum rewritable count by the comparison, it outputs an alarm signal (ALARM) to the outside.

On the other hand, the AND circuit 22 inhibits the output of the write enable signal to the memory cell array 20 and the counter circuit 23 when the comparison circuit 21 detects the coincidence of the data, so that the external data is written in the memory cell array 20. It will not be crowded. At this time, the counter circuit 23 does not count up.

As described above, the number of times the external data is written in the memory cell array 10 is counted by the counter circuit 11 in the non-volatile memory 1, and when the count value exceeds the maximum rewritable number, an alarm signal is issued. Is output, it is possible to know the life of the memory cell array 10 without increasing the amount of hardware and reducing the throughput of the system.

When the comparison circuit 21 detects that the data from the outside is the same as the data inside the memory cell array 20, the memory cell array 2 of the data from the outside is detected.
The AND circuit 22 inhibits writing to 0, and the counter circuit 23 in the nonvolatile memory 2 counts the number of times external data is written in the memory cell array 20,
By outputting an alarm signal when the count value exceeds the maximum rewritable number, the number of writing to the memory cell array 20 can be reduced and
The life of the memory cell array 20 can be known. Therefore, the normal operation time until the maximum number of rewritable times of the nonvolatile memory 2 is reached can be lengthened, and the life of the nonvolatile memory 2 can be extended.

In this case, since the comparison and judgment of the data from the outside and the data in the memory cell array 20 are realized by the hardware, the processing for extending the life of the non-volatile memory by the software of the microcomputer becomes unnecessary, The software can be easily created, and the throughput of the system incorporating the nonvolatile memory can be improved.

[0030]

As described above, according to the non-volatile memory of the present invention, the non-volatile memory having the upper limit of the number of data rewrites is provided with the counting means for counting the number of data rewrites. There is an effect that it is possible to know the life of the memory cell without increasing the number of cells and reducing the throughput of the system.

According to another non-volatile memory of the present invention, a non-volatile memory having an upper limit on the number of times of rewriting data is compared with a comparison means for comparing the externally written data with the internally written data. By providing a means for suppressing the writing of write data from the outside when a mismatch is detected by this comparison and a means for counting the number of times writing has been performed, a long service life is achieved without reducing the system throughput. There is an effect that the life of the memory cell can be known by increasing the efficiency.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a block diagram showing the configuration of another embodiment of the present invention.

[Explanation of symbols]

 1, 2 Non-volatile memory 10, 20 Memory cell array 11, 23 Counter circuit 21 Comparison circuit 22 AND circuit

Claims (4)

[Claims] 1. A non-volatile memory having an upper limit on the number of times of rewriting data, comprising a counting means for counting the number of times of rewriting of the data. 2. The non-volatile memory according to claim 1, further comprising means for outputting alarm information when the count value of the counting means reaches the upper limit number of times. 3. A non-volatile memory having an upper limit for the number of times data is rewritten, the comparing means comparing externally rewritten data with internally written data, and the comparison means detects a match. And a counting means for counting the number of times the rewriting data from the outside has been written to the inside. memory. 4. The non-volatile memory according to claim 3, further comprising means for outputting alarm information when the count value of the counting means reaches the upper limit number of times.