JP2000222889A - Method for erasing and writing memoy and storage medium recording memory erasing and writing programs - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the number of times of rewriting in a nonvolatile memory capable of rewriting a plurality of times. SOLUTION: This method for erasing and writing a memory comprises the steps of retrieving the number of accumulated times of rewriting so far in the memory for erasing and writing (S101), then outputting erasing and writing enabling command (S102), and actually starting erasing and writing (S103). In this case, a time required for the erasing and writing is largely changed according to the number of accumulated times of rewriting at the time point. This method further comprises the steps of dealing with a pulse width for deciding the time required for the erasing and the writing variably by table data and a calculation (S104), inserting a queuing time for the calculated pulse width (S105), thereafter newly registering number of times of accumulated rewriting (S106), and inhibiting the erasing and the rewriting (S107).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to a semiconductor or a device equipped with a nonvolatile memory that can be rewritten a plurality of times, and a memory erasing / writing method for erasing / writing a memory, and a memory. The present invention relates to a storage medium on which a memory erase / write program is recorded.

[0002]

2. Description of the Related Art Due to the characteristics of a nonvolatile memory which can be rewritten a plurality of times, the time required for erasing / writing increases as the number of rewriting increases.

In the conventional method, as shown in the graph of FIG. 7, since the pulse width, which is the waiting time during erasing and writing, is constant, the point at which the erasing / writing time intersects with the fixed pulse width is the upper limit of the number of rewriting. Had become.

If the time required for erasing / writing exceeds the time of the fixed pulse width, rewriting cannot be performed as the life of the memory.

[0005]

A system equipped with a nonvolatile memory which can be rewritten a plurality of times is frequently used in a system for changing data after completion of a product, and updates control software, changes data, and the like. That is, increasing the number of rewritable times is directly linked to extending the life of the product.

However, in a conventional non-volatile memory which can be rewritten a plurality of times, the pulse width is constant, so that a memory having a small number of times of rewriting uses a wasteful waiting time. In addition, the number of times of rewriting was small, and the life of the product was short.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and provides a memory erasing / writing method capable of reducing wasteful waiting time and dramatically increasing the maximum number of times of rewriting. The purpose is to provide a medium.

[0008]

In order to achieve the above object, the present invention comprises a step of checking the number of times of erasing and writing, and a table data and a waiting time during erasing and writing according to the number of times. It is characterized by comprising a pulse width variable step of making variable by calculation and a step of registering the number of times of erasing and writing.

Further, the present invention provides an erasing / writing experimental step of attempting erasing / writing on a part of a memory, and a waiting time during erasing / writing when the erasing / writing has not been performed in the erasing / writing experimental step. And increasing the waiting time.

According to the above-mentioned method, it is possible to reduce a useless waiting time at the time of erasing / writing the memory, and it is possible to increase the maximum number of times of rewriting.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a flowchart for explaining a variable pulse width memory write control for explaining a first embodiment of the present invention. This first embodiment is a method of making the pulse width variable according to the number of times of rewriting.

In FIG. 1, first, in S101,
A search is made for the cumulative number of times of rewriting of the memory to be erased / written. Subsequently, in S102, an erasing and writing permission command is issued, and in S103, erasing and writing are actually started. Since the time required for erasing / writing greatly changes depending on the cumulative number of rewritings at that time, the pulse width for determining the time required for erasing / writing is made variable by table data and calculation in S104.

Then, S is calculated by the calculated pulse width.
At 105, a waiting time is entered. Thereafter, in S106, the cumulative number of rewrites is newly registered, and in S107, erasure / rewrite is prohibited.

FIG. 2 shows the relationship between the number of rewrites and time at this time. In this way, by making the waiting time from erasing / writing to the next processing variable, the upper limit number of rewriting can be increased. Further, the erasing / writing processing time can be shortened by eliminating useless waiting time. In addition, the upper limit of the rewriting time or the upper limit of the number of rewriting can be set freely according to the customer's request. In the graph of FIG. 2, r1 indicates the number of times of rewriting when the upper limit of the rewriting time is set to t1.

As shown in the graph of FIG. 3, a fixed pulse width is used up to the point where the required erase / write time, which is called a switching point hereinafter, increases in a quadratic curve, and thereafter a variable pulse width is used. It is also possible to This method will be described with reference to the flowchart of FIG.

In FIG. 4, in the number search step of S401, the cumulative number of rewrites so far of the memory to be erased / written is searched, and in S402, an erasure / write permission command is issued. Start. At this time, it is determined whether or not the accumulated number of times exceeds the number of rewriting of the switching point in S4.
If it is determined that the value exceeds the value (Yes in S404)
s) In steps S406 and S407, the pulse width is made variable by table data and calculation, and a waiting time is entered. If it does not exceed the switching point (No in S404), a fixed pulse width is given in S405 and S
At 407, time waiting is performed. Then, the cumulative number of rewrites is registered in S408, and erasure / rewrite is prohibited in S409.

FIG. 5 is a flowchart relating to a variable pulse width memory write control for explaining a second embodiment of the present invention. In the second embodiment, the pulse width is made variable by judging from the number of rewrites. Instead, an experimental area is actually provided in the memory, and an erasing / writing experiment is first performed in that area.

In FIG. 5, an area to be tested first is set in S501. Subsequently, in S502, an erase / write experiment is performed in the experiment area. The contents of this experiment are shown in the flowchart of FIG.
In step S1, an erase / write permission command is issued, and in step S602, the erase / write is actually started. In step S603, the control waits for the pulse width set at the present time,
In step S604, the erasure / writing is prohibited, and the experiment ends.

From the experimental results based on the flow of FIG.
In S3, it is confirmed whether or not the experiment is successful. If the experiment is successful (Yes in S503), an erasing / writing permission command is issued in S504, and erasing / rewriting is actually started in S505. In step S506, the process waits for a time corresponding to the pulse width set in step S506.
Prohibit rewriting.

If the experiment is not successful in S503 (No in S503), the pulse width is extended in S508, the experiment area is changed in S509, and the experiment is performed again.

The reason for changing the experimental area is that if the cumulative number of rewrites of the non-volatile memory to be rewritten is a certain number (i times), the time required for erasing / writing changes depending on the number of rewrites. If the cumulative number of rewrites is not the same i, the mismatch will occur.

It is assumed that an experiment for the i-th rewriting is actually performed in S502 of FIG. Consider a case where it is determined that the experiment has failed in the determination in S503. If S50
If the experiment area is not changed in step 9,
At 502, the area to be tested is the (i + 1) -th erasure /
Writing is performed, and there is a difference between the number of times of actual rewriting and the number of times of rewriting. The difference increases as the number of failures increases. Therefore, by changing the experimental area in S509 to an area in which the total number of times of rewriting is equal to the area to be actually rewritten, the optimal experiment can be performed in S502. If the experiment is successful in S503, the optimal design specified in S508 is performed. Erase / write can be actually performed with a proper pulse width.

A memory erasing / writing program consisting of data corresponding to each step constituting the first and second embodiments is recorded on a recording medium and processed by a computer.

[0025]

As described above, according to the present invention, by making the waiting time from erasing / writing to the next processing variable, the upper limit number of rewriting can be increased, and the erasing / writing processing time can be reduced. , And can be shortened by eliminating useless waiting time. Further, the upper limit of the rewriting time or the upper limit of the number of rewriting can be set arbitrarily.

[Brief description of the drawings]

FIG. 1 is a flowchart related to a variable pulse width memory write control for explaining a first embodiment of the present invention;

FIG. 2 is a graph showing the relationship between the rewriting time and the number of rewriting when the control method of FIG. 1 is used.

FIG. 3 is a graph showing the relationship between the rewrite time and the number of rewrites when a fixed pulse width is used up to a switching point and a variable pulse width is used in the first embodiment of the present invention.

FIG. 4 is a flowchart relating to variable pulse width memory write control in the case where control is performed as shown in FIG. 3;

FIG. 5 is a flowchart of a variable pulse width memory write control for explaining a second embodiment of the present invention;

FIG. 6 is a flowchart showing details of some of the steps in FIG. 5;

FIG. 7 is a graph showing the relationship between the rewrite time and the number of rewrites when a conventional fixed pulse width is used.

[Explanation of symbols]

S101, S401 Cumulative count step S102, S402, S504, S601 Erase / write permission step S103, S403, S505, S602 Erase / write start step S104, S406 Variable pulse width setting step S105, S407, S506, S603 Time wait step S106, S408 Cumulative rewrite number registration step S107, S409 Erase / rewrite prohibition step S404 Switching point rewrite number determination step S405 Fixed pulse width setting step S501 Initial experiment area setting step S502 Erase / write experiment step S503 Experiment success judgment step S507, S604 Erase / Rewrite Write inhibit step S508 Pulse width increase step S509 Experimental area change step

Claims (4)

[Claims] In a memory erasing / writing method for erasing / writing a nonvolatile memory which can be rewritten a plurality of times, a step of examining the number of times of erasing and writing is performed; A method for erasing and writing data in a memory, comprising: a pulse width changing step of making the waiting time during erasing and writing variable by table data and calculation; and a step of registering the number of times of erasing and writing. 2. A memory erasing / writing method for performing memory erasing / writing on a nonvolatile memory which can be rewritten a plurality of times. And a waiting time increasing step for extending a waiting time during erasing and writing when writing and erasing have not been performed in the erasing / writing experiment step. 3. A storage medium storing a memory erasure / write program for performing memory erasure / write on a nonvolatile memory which can be rewritten a plurality of times,
A step of examining the number of times of erasing and writing, a step of changing a pulse width for varying a waiting time during erasing and writing according to the number of times by table data and calculation, and a step of registering the number of times of erasing and writing. A storage medium on which a memory erasing / writing program is recorded. 4. A storage medium in which a memory erase / write program for performing memory erase / write on a nonvolatile memory which can be rewritten a plurality of times is recorded.
In the erase / write experiment step of trying to erase and write to a part of the memory,
A storage medium storing a memory erase / write program, characterized by recording data having a wait time increasing step for extending a wait time during erasing and writing.