JPH06236695A - Non-volatile memory device with exchange display function - Google Patents

Abstract

PURPOSE:To enable the sure exchange of a memory device before the rewriting of data can no longer be made by providing an exchange time display circuit making display in such a manner that the conversion of the device is executed in accordance with the output signal above the limit value of the number of rewriting times from a comparator circuit. CONSTITUTION:The writing effective command signal inputted to the memory device 10 is detected by a rewriting operation detecting circuit 21 and a rewriting operation detection signal B is outputted. A number of rewriting times memory circuit 23 acids the number of rewriting times of a counter output signal C to the previously held number of rewriting times and stores the accumulated number of times. A non-volatile memory element having the limit value of the number of rewriting times equal to or higher than the limit value of the number of rewriting times of the memory element within the device 10 is used for the memory element to be used in this circuit 23. The accumulated number in the number of rewriting times memory circuit 23 and the limit value of the number of rewriting times are then transmitted to a comparator 24. The number of rewriting times output signal D of the circuit 23 and the output signal E of the limit value of the number of rewriting times are received and compared in the circuit 24. The circuit 24 displays 25 the signal F when the signal D rises to E or above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a memory device using a nonvolatile memory element such as an EEPROM or a flash memory which has a limited number of times of writing.

[0002]

2. Description of the Related Art Conventionally, a device of this kind is composed of a control unit for controlling the device and a memory unit for storing data, and reads / writes data from / to a nonvolatile memory element in the memory unit. It is a thing. FIG. 3 is a block diagram showing a configuration example of such a conventional nonvolatile memory device.

In this figure, 1 is an address decoder for selecting each memory element, 2 is a control circuit for controlling the read / write of data, and 3 is a memory section for holding it. A is a data bus for inputting / outputting data, B is an address bus for inputting an address, C is a chip select signal for selecting each mounted memory element, and D is for controlling the address decoder 1. Decoder control signal for enabling, E is an output enable signal for enabling data output, F is a write enable signal for enabling data writing, G is data writing for controlling external data writing In the signal, H is a data read signal for controlling the data read from the outside.

Therefore, when data is written, when a specified address of the storage area is input from the address bus B and the external data write signal G is enabled, the read / write control circuit 2 controls the address decoder 1 to perform decoder control. The signal D is output, and the write enable signal F is output to the memory unit 3. The address decoder 1 receiving the specified address and the decoder control signal D input from the address bus B outputs the chip select signal C for selecting the memory element specified by the address to the memory unit 3. Chip select signal C and write enable signal F
The memory element in the memory unit 3 that receives the data writes and stores the data input from the data bus A.

[0005]

However, in the conventional memory device described above, the memory section 3 shown in FIG. 3 is used.
The memory device has a limit to the number of times data can be rewritten. If this limit is exceeded, the memory device cannot be used.
I was replacing the device. However, in the current memory device, it is not possible to know exactly when to replace the memory device. Therefore, when replacing the memory device, the period during which the number of data writes to the memory device of the system using the memory device does not reach the limit is estimated in advance. I was replacing the memory device.

However, according to this method, the limit period changes depending on the operating condition of the system. Therefore, if the operating rate of the system is higher than the estimate in advance, the system will be exceeded until the device is replaced and the system is down. There was something to do. SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned problems and provide a nonvolatile memory device with a replacement display function that can accurately display the replacement time of a memory device in accordance with the number of times data is written to the memory.

[0007]

In order to achieve the above object, the present invention provides a non-volatile memory device using a non-volatile memory element, which detects a rewriting operation every time data is written to the memory element. A circuit, a rewrite frequency counter that counts the number of rewrites to the memory element based on an output signal from the rewrite operation detection circuit, and an output signal from the rewrite frequency counter,
A rewrite frequency storage circuit that stores the cumulative number of times counted before, a comparison circuit that compares the rewrite frequency from the rewrite frequency storage circuit with a rewrite frequency limit value of the memory element, and a comparison circuit from the comparison circuit. A replacement time display circuit is provided to indicate that the device is to be replaced based on an output signal that is equal to or greater than the rewrite count limit value.

[0008]

According to the present invention, as described above, the number of times of rewriting is counted every time data is written to the memory element, the number of times of rewriting is accumulated and stored, and the number of times of rewriting is
The number of rewrites is compared with the limit value, and when the number of rewrites exceeds the limit value, it is displayed so that the device can be replaced.Therefore, the memory device must be replaced before the data cannot be rewritten. can do.

As a result, it is possible to surely prevent the device from becoming unusable by rewriting the data more than the limit value and destroying the data in the device.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a block diagram of a nonvolatile memory device with an exchange display function showing an embodiment of the present invention.
In the figure, 10 is a memory device, and this memory device 10 comprises a memory unit 11 and a control unit 12. Reference numeral 21 is a rewrite operation detection circuit, 22 is a rewrite number counter, 23 is a rewrite number storage circuit, 24 is a comparison circuit, and 25 is a replacement time display circuit.

A is a write enable signal, B is a rewrite operation detection signal, C is a counter output signal, D is a rewrite count output signal, E is a rewrite count limit value output signal, and F is a comparison circuit output signal. Therefore, the rewrite operation detection circuit 2
1 is connected to the memory device 10 by a write enable signal line to which the write enable signal A is sent,
The rewrite operation detection signal line to which the rewrite operation detection signal B is sent is connected to the rewrite number counter 22. The rewrite number counter 22 is connected to the rewrite number storage circuit 23 by a counter output signal line to which the counter output signal C is sent. The rewrite frequency storage circuit 23 is connected to the comparison circuit 24 by a rewrite frequency output signal line to which the rewrite frequency output signal D is sent.

On the other hand, the comparison circuit 24 is connected to a rewrite number limit value output signal line to which the rewrite number limit value output signal E is input. The output signal line of the comparison circuit 24 is connected to the replacement time display circuit 25, and the comparison circuit output signal F is sent to the replacement time display circuit 25. Next, the operation of the nonvolatile memory device with the exchange display function showing the embodiment of the present invention will be described with reference to FIG.

First, when data is written to the memory device (step S1), the write enable signal A is input to the memory device 10. Then, the rewrite operation detection circuit 21 monitors the operation of the write enable signal A input to the memory device 10 and detects that data is written in the memory element (step S2). Memory device 1
When the memory element in 0 is an EEPROM, data is written when the write enable signal A is asserted and the interval until it is asserted is more than ten nanoseconds (nanoseconds). The circuit 21 detects the interval (step S2) and outputs the rewrite operation detection signal B (step S3) assuming that the data has been rewritten.

When the memory device in the memory device 10 is a flash memory, the write execution command signal input to the memory device 10 is detected by the rewrite operation detection circuit 21 (step S2), and the rewrite operation detection signal B is output. (Step S3). The rewrite number counter 22 counts the rewrite operation detection signal B and outputs the rewrite number as a counter output signal C (step S4). The rewrite number storage circuit 23 adds the number of rewrites of the counter output signal C to what was previously held by an adder and stores the cumulative result (step S5). This rewrite frequency storage circuit 2
As the memory element used in No. 3, a non-volatile memory element having a rewrite count limit value equal to or greater than the memory element in the memory device 10 is used.

Next, the cumulative number in the rewrite frequency storage circuit 23 and the rewrite frequency limit value are transmitted to the comparison circuit 24 (step 6), and the comparison circuit 24 outputs the rewrite frequency output signal D of the rewrite frequency storage circuit 23. , Rewrite count limit value output signal E
Is received (step S7), and both are compared. When the rewrite number output signal D becomes equal to or more than the rewrite number limit value output signal E (step S8), the rewrite number comparison circuit 24 outputs the comparison circuit output signal F to the replacement time display circuit 25.
Replacement time display circuit 25 receiving the comparison circuit output signal F
Displays a message prompting the replacement of the memory device such as turning on the LED (step S9).

The present invention is not limited to the above embodiments, and various modifications can be made within the scope of the present invention, and these modifications are not excluded from the scope of the present invention.

[0017]

As described above in detail, according to the present invention, a rewrite operation detecting circuit for detecting a rewrite operation every time data is written to a memory element, and an output signal from the rewrite operation detecting circuit are used. A rewrite frequency counter that counts the number of rewrites to the memory element, and a rewrite frequency storage circuit that stores the cumulative number of the recount frequency based on the output signal from the rewrite frequency counter. A comparison circuit that compares the number of times of rewriting from the number of times memory circuit with a limit value of the number of times of rewriting of the memory element, and a message indicating that the device should be replaced based on an output signal from the comparison circuit that is equal to or greater than the limit number of times of rewriting Since the replacement time display circuit is provided, the memory device can be reliably replaced before the data cannot be rewritten.

As a result, it is possible to prevent the device from becoming unusable by rewriting the data over the limit value and destroying the data in the device.

[Brief description of drawings]

FIG. 1 is a block diagram of a nonvolatile memory device with an exchange display function according to an embodiment of the present invention.

FIG. 2 is an operation flowchart of the nonvolatile memory device with a replacement display function according to the embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration example of a conventional nonvolatile memory device.

[Explanation of symbols]

 10 memory device 11 memory unit 12 control unit 21 rewriting operation detection circuit 22 rewriting frequency counter 23 rewriting frequency storage circuit 24 comparison circuit 25 replacement time display circuit A write enable signal B rewriting operation detection signal C counter output signal D rewriting frequency output signal E Rewrite count limit value output signal F comparison circuit output signal

Claims (1)

[Claims] 1. A non-volatile memory device using a non-volatile memory element, comprising: (a) a rewriting operation detection circuit for detecting a rewriting operation every time data is written to the memory element;
(B) A rewrite frequency counter that counts the number of rewrites to the memory element based on the output signal from the rewrite operation detection circuit; and (c) counts forward based on the output signal from the rewrite frequency counter. And (e) a comparison circuit for comparing the number of rewritings from the rewriting number storage circuit with a rewriting number limit value of the memory element, and (e) the comparison. A non-volatile memory device with a replacement display function, comprising a replacement timing display circuit for displaying that the device is to be replaced based on an output signal from the circuit that is equal to or greater than a limit value of the number of times of rewriting.