JPH01138697A - Nonvolatile semiconductor memory - Google Patents

Abstract

PURPOSE:To estimate the life of a memory to prevent accidents by providing a means where the number of times of write to an electrically erasable nonvolatile semiconductor memory is stored and is read out to the external. CONSTITUTION:An erasing circuit 4 is driven from an internal terminal 41 to initialize a nonvolatile memory 3. The output of the memory 3 is sent to a counter 2, and the counter 2 is counted up by one at each time of erase and write of a nonvolatile memory 1. Thereafter, contents of the counter 2 are written in the memory 3 at the time of detecting power-off, and contents of the memory 3 are loaded on the counter 2 at the time of detecting power-on. Thus, the accumulated number of times of write to the memory 1 is stored in the memory 3 and is monitored from an output terminal 23, and it is read out to the external.

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 means for externally determining its life span 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 that the invention seeks to solve]

Therefore, there is a drawback that it is not known until a problem occurs during actual use.

An object of the present invention is to provide a nonvolatile semiconductor memory that solves the above problems.

[Means for solving problems]

The present invention is an electrically erasable non-volatile semiconductor memory characterized by including a counter for counting the number of writes, a non-volatile storage section for storing the counted value, and means for reading the counted value from the outside. This is a non-volatile semiconductor memory.

〔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 an original non-volatile memory, 2 is a counter for counting the number of writes, and 3 is a non-volatile memory for storing the output of the counter 2, the output 32 of which is connected to the input 21 of the counter 2. 4 is an erase circuit.

The output 22 of the counter 2 is output to the output terminal 23 at the same time as the input 31 of the nonvolatile memory 3. However, the number is n. The erase input 33 of the nonvolatile memory 3 includes an erase circuit 4.
The output 42 of the erase circuit 4 is connected, and the input 41 of the erase circuit 4 is connected to an internal terminal.

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 one time, it is desirable to output the data to an external terminal to avoid erasing it again due to an erroneous operation. Even when nonvolatile memory 1 is erased, 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 rOFFJ, the contents of the counter 2 are written to the nonvolatile memory 3. Conversely, if it detects that the power supply becomes roNJ,
Load the contents of non-volatile memory 3 into 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, ie, the cumulative number of writes, is stored in the nonvolatile memory 3.

〔Effect of the invention〕

As explained above, in the present invention, by monitoring the cumulative number of writes from the output terminal, it is possible to know whether the electrical write limit has been exceeded, and therefore, it is possible to take measures such as replacement before an actual failure occurs. This has the effect of preventing accidents in advance.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. 1.3...Nonvolatile memory 2...Counter 4.
・Erasing circuit

Claims (1)

[Claims] (1) An electrically erasable nonvolatile semiconductor memory, characterized by including a counter that counts the number of writes, a nonvolatile storage section that stores the counted value, and means for reading the counted value from the outside. Non-volatile semiconductor memory.