JPH01220300A - Nonvolatile semiconductor memory - Google Patents

Abstract

PURPOSE:To recognize the limitation of the number of times of write from the outside and to guarantee a write operation by containing a counter for counting the number of times of write, a nonvolatile storage part for storing a count value, and a means for monitoring the excess of the count value over a prescribed count value from the outside. CONSTITUTION:The counter 2 is counted up by one at every erasure and write of a nonvolatile memory 1. Afterwards, in case of detecting the OFF of a power source, the content of the counter 2 is written on a nonvolatile memory 3, and adversely, when the ON of the power source is detected, the content of the nonvolatile memory 3 is loaded on the counter 2. Thenceforth, the counter 2 is counted up by one at every erasure and write of the nonvolatile memory 1, and thus, the accumulated number of times of write on the nonvolatile memory 1 is stored in the nonvolatile memory 3. And since the output of a comparator 5 changes when the value exceeds a critical value, it is possible to recognize the limitation from the outside easily by monitoring the change from an output terminal 23. In such a way, the write can be guaranteed as the one effective electrically.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrically erasable nonvolatile semiconductor memory, and more particularly to a memory having a function of externally monitoring its lifespan based on the number of writes.

[Conventional technology]

Conventionally, this type of non-volatile semiconductor memory has a limit on the number of times it can be erased and written, but there was no way to know this from the outside.

[Problem to be solved by the invention]

Therefore, there is a drawback that a problem is not known until it occurs during actual use.6 An object of the present invention is to provide a nonvolatile semiconductor memory that solves the above problems.

[Means to solve the problem]

In order to achieve the above object, the non-volatile semiconductor memory of the present invention includes a counter that counts the number of writes, a non-volatile storage section that stores the counted value, and an external monitor that monitors whether a predetermined counted value has been exceeded. and means to do so.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

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

1 is the original non-volatile memory (storage unit), 2 is a counter that counts the number of writes, 3 is a non-volatile memory (storage unit) that stores the output of counter 2, and its output 32 is connected to the input 21 of counter 2. has been done.

Further, 4 is an erase circuit, and 5 is a comparator. The output 22 of the counter 2 is connected simultaneously to the input 31 of the non-volatile memory 3 and to the input 52 of the comparator 5.

However, the number of pieces is n. The output 42 of the erasing circuit 4 is connected to the erasing power 33 of the nonvolatile memory 3, and the input 41 of the erasing circuit 4 is connected to an internal terminal.

The other input 51 of the comparator 5 is set with a guaranteed limit value of this nonvolatile memory. The output of the comparator 5 is connected to an external output terminal 23 for externally monitoring a predetermined count value.

Next, its operation will be explained.

First, the erase circuit 4 is driven from the internal terminal 41 to initialize the nonvolatile memory 3. Since this is performed only - times, it is desirable to output the data to the external output terminal 23 to avoid erasing it again due to an erroneous operation. and non-volatile memory 1
Even when erasing the data, the nonvolatile memory 3 is not erased.

Next, the output of the non-volatile memory 3 (currently initialized to 0) is loaded into the counter 2. Thereafter, the counter 2 is incremented by one each time the nonvolatile memory 1 is erased or written. After that, when it is detected that the power becomes rOFF J, the contents of the counter 2 are written into the nonvolatile memory 3. Conversely, when it is detected that the power is turned on, the contents of the nonvolatile memory 3 are loaded into the counter 2. After that, the counter 2 is incremented once each time the nonvolatile memory 1 is erased or written in the same manner. In this way, the total number of writes to the nonvolatile memory 1, that is, the cumulative number of writes, is stored in the nonvolatile memory 3. The latest cumulative number of writes is stored in the counter 2, and when this value exceeds the limit value, the output of the comparator 5 changes, so by monitoring this change from the output terminal 23, you can easily know from the outside. Can be done.

〔Effect of the invention〕

As described above, the present invention can ensure that writing is electrically effective by monitoring from the output terminal whether the cumulative number of writes has been exceeded.

Therefore, by taking measures such as replacing the product before it actually becomes defective, it is possible to prevent accidents in advance.

[Brief explanation of the drawing]

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

Claims (1)

[Claims] 1. In an electrically erasable non-volatile semiconductor memory, a counter that counts the number of writes, a non-volatile storage section that stores the counted value, and means for externally monitoring whether a predetermined counted value has been exceeded. A nonvolatile semiconductor memory characterized by comprising: