JP2001014865A - Flash memory, flash memory rewriting frequency storing method and computer readable recording medium recorded with program making computer execute the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the cost of a flash memory by reducing the burden of a user and a user software and enhancing the reliability of rewriting frequency information and reducing a memory area for storing the rewriting frequency. SOLUTION: This flash memory is provided with a general flash memory ROM area 2 where various data are to be stored and a monitor area 3 where is installed apart from the general flash memory RAM area 2 and where the rewriting frequency of the area 2 is to be stored and where a security function prior to the executing of an erasing operation is higher than that in the area 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flash memory for recording the number of rewrites, a flash memory rewrite number storage method, and a computer-readable recording medium for recording a program for causing a computer to execute the method. The present invention relates to a flash memory for recording the number of rewrites in a flash memory, a flash memory rewrite number storage method, and a computer-readable recording medium in which a program for causing a computer to execute the method is recorded.

[0002]

2. Description of the Related Art In recent years, flash memories, which are writable nonvolatile memories, have been widely used. Flash memory is cheap and fast,
Since the number of times of rewriting is limited, it is necessary to record and manage the number of times of rewriting. By the way, there is known a conventional flash memory in which the number of rewrites is recorded in the flash memory.

FIG. 12 is an explanatory diagram showing a schematic configuration of a conventional flash memory. In a conventional flash memory, an arbitrary block 51 in the entire memory 50 is used to store the number of times of rewriting of the flash memory. Next, the operation of the conventional flash memory will be described. In the conventional flash memory, every time rewriting is performed, information indicating rewriting is written in the block 51 by user software programmed by the user. Here, in the conventional flash memory, additional writing to one writing unit is not allowed, so that writing of information indicating one rewriting requires a memory area for one writing unit.

[0004]

However, according to the above-mentioned prior art, each time rewriting is performed, block 5 is rewritten.
Since the function of writing to 1 is realized by user software programmed by the user, there is a problem that the load on the user and the user software increases. Further, since the block 51 for storing the number of times of rewriting of the flash memory is a general-purpose block, there is a high possibility that the number of times of rewriting is erased due to erroneous writing or the like, and the reliability of the number of times of rewriting (information indicating the number of times of rewriting) is high. However, there was a problem such that the number of samples decreased. In addition, 1
Writing information indicating the number of times of rewriting of the flash memory requires a memory area for one writing unit, so a large memory area obtained by multiplying the number of times of rewriting and the writing unit is required, thereby increasing costs. was there.

The present invention has been made in view of the above, and has been made to reduce the load on the user and the user software, improve the reliability of the rewrite frequency information, and reduce the memory area for storing the rewrite frequency. It is another object of the present invention to provide a flash memory that reduces costs, a flash memory rewrite frequency storage method, and a computer-readable recording medium that stores a program that causes a computer to execute the method.

[0006]

Means for Solving the Problems To solve the above-mentioned problems,
In order to achieve the object, in the flash memory according to the present invention, a normal storage means for storing various data,
The security function is provided separately from the normal storage means, stores the number of times of rewriting of the normal storage means, and has a security function until the execution of an erasing operation is performed more frequently than the normal storage means. I do.

According to the present invention, the number-of-times storage means, which is provided separately from the normally used normal storage means and has a high security function, stores the number of rewrites of the normal storage means. This can reduce the possibility that the rewrite frequency information (information indicating the rewrite frequency) is lost due to erroneous writing or the like.

[0010] In the flash memory according to the next invention, a normal storage means for storing various data and a normal storage means are provided separately, and the number of rewrites of the normal storage means is stored and erased by a user. And a number storage means having no function.

According to the present invention, the number-of-times storage means provided separately from the normally used normal storage means and having no user erasing function stores the number of times of rewriting of the normal storage means. As a result, the possibility that the rewrite frequency information is lost due to erroneous writing or the like can be reduced.

[0010] In the flash memory according to the next invention, the number storage means is capable of additionally writing.

According to the present invention, additional writing to the number-of-times storage means can be performed, and writing can be performed not for each writing unit but for each bit.

[0012] In the flash memory according to the next invention, a normal storage means for storing various data, a number storage means for storing the number of rewrites of the normal storage means, and a flash memory for rewriting the normal storage means. Control means for updating the number of rewrites stored in the number storage means,
It is characterized by having.

According to the present invention, instead of the user software, the control means updates the number of times of rewriting stored in the number storage means provided separately from the normal storage means normally used. This eliminates the need to implement the function of updating the number of times of rewriting by user software, prevents erroneous writing due to a program error, and reduces the possibility that the number of times of rewriting is lost.

[0014] In the flash memory according to the next invention, the number-of-times storage means can perform additional writing, and the control means sets the number-of-times storage means every time the data storage means is rewritten. , Find the boundary between the written and unwritten bits,
It is characterized in that writing of one bit to the number storage means is performed in a predetermined order.

According to the present invention, additional writing can be performed on the number-of-times storage means, and the control means can control whether the written bits and the unwritten bits of the number-of-times storage means each time the data storage means is rewritten. A bit to be written is determined by searching for a boundary between the bits, and one bit is sequentially written. This allows
Writing can be performed not for each writing unit but for each bit.

In the flash memory according to the next invention, the number storage means is a single block.

According to the present invention, when the number-of-times storage means is a single block, the possibility that the number-of-times-of-rewriting information is lost due to erroneous writing or the like can be reduced.

In the flash memory according to the next invention, the number storage means is one word line area.

According to the present invention, even when the number-of-times storage means is one word line area, the possibility that the number-of-times-of-rewriting information is lost due to erroneous writing or the like can be reduced.

In the flash memory according to the next invention, the number storage means is a plurality of word line regions, and each word line region corresponds to each digit of the number of rewrites. I do.

According to the present invention, the plurality of word line regions correspond to each digit of the number of times of rewriting. This further
The memory area for storing the number of rewrites can be reduced.

The flash memory according to the next invention further comprises an alarm unit for issuing an alarm when the number of rewrites stored in the number storage unit exceeds a preset number. I do.

According to this invention, the alarm means issues an alarm when the number of rewrites stored in the number-of-times storage means exceeds a preset number. As a result, the user can be notified that the number of rewrites has exceeded the guaranteed number of rewrites.

In the flash memory according to the next invention, the number-of-times storage means stores the number of times of rewriting for each block of the normal storage means for which rewriting is permitted.

According to the present invention, the number-of-times storage means stores, for each block of the normal storage means, for which rewriting is permitted,
The number of times of rewriting can be stored, and the number of times of rewriting can be managed for each block.

In a flash memory rewrite frequency storage method according to the next invention, the flash memory rewrite frequency storage method for storing a rewrite frequency in a flash memory provided with a frequency storage means for storing the rewrite frequency. A search step of searching for a boundary between a written bit and a non-written bit in the number storage means each time the flash memory is rewritten; and the number storage means based on a search result in the search step. Updating one bit of data in a predetermined order.

According to the present invention, each time the flash memory is rewritten, the boundary between the written bit and the unwritten bit in the count storage means is searched to determine the write bit, and the count is sequentially determined. 1-bit writing to the storage means is performed. As a result, writing can be performed not for each writing unit but for each bit.

In the flash memory rewriting number storage method according to the next invention, the number storage means comprises a plurality of word line regions corresponding to each digit of the number of rewritings. In addition, the word line area corresponding to the lower digit is cleared, and one bit is written to the word line area corresponding to the upper digit.

According to the present invention, a plurality of word line regions are assigned to each digit of the number of rewrites,
The word line area corresponding to the lower digit is cleared, and one bit is written to the word line area corresponding to the upper digit. Thereby, the memory area for storing the number of times of rewriting can be further reduced.

A computer-readable recording medium according to the next invention is characterized by recording a program for causing a computer to execute the method according to the above-described invention.

According to the present invention, it is possible to reduce the memory area for storing the number of times of rewriting by causing a computer to execute the method according to the above-described invention.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a flash memory, a flash memory rewrite frequency storage method, and a computer-readable recording medium storing a program for causing a computer to execute the method will be described in detail with reference to the drawings. Will be described. The present invention is not limited by the embodiment.

Embodiment 1 FIG. 1 is a block diagram illustrating a schematic configuration of a flash ROM (flash memory) according to the first embodiment of the present invention. The flash ROM 1 according to the first embodiment has a normal flash ROM area 2 for storing various data and a monitor memory for storing the number of times of rewriting (hereinafter sometimes simply referred to as “rewriting”) the normal flash ROM area 2. An area 3, a control section 4 for controlling the flash ROM 1, and a data address bus 5 for connecting the above sections are provided. The monitor memory area 3 is composed of one word line area, and is set to permit additional writing.

Writing of the rewrite frequency information (information indicating the normal rewrite frequency of the flash ROM area 2) to the monitor memory area 3 is performed by user software programmed by the user. Here, the monitor memory area 3 is provided separately from the normal flash ROM area 2 so that the user software does not accidentally erase the rewrite frequency information. It is set higher than the normal flash ROM area 2. Specifically, the erasing procedure is different from that of the normal flash ROM area 2,
The erasing function by the user is eliminated, so that the erasing operation cannot be performed by the user. The normal flash ROM area 2 corresponds to the normal storage means of the present invention, and the monitor memory area 3 corresponds to the number storage means of the present invention.

The operation of the first embodiment in the above configuration will be described with reference to FIGS. FIG.
6 is a flowchart showing a flow of a rewriting operation by user software according to the first exemplary embodiment; The user software first performs a write process on the monitor memory area 3 (S1), and then rewrites the normal flash ROM area 2 (S2). That is, each time the normal flash ROM area 2 is rewritten, a write process to the monitor memory area 3 is performed.

In the monitor memory area 3, additional writing is permitted, and the number of rewrites is indicated for each bit on a word line basis, so that the memory usage can be minimized. The reliability problem caused by permitting additional writing can be solved by retrieving the previous writing bit at the time of rewriting because the last writing data is guaranteed. FIG. 3 is a flowchart illustrating a flow of a writing process to the monitor memory area 3 according to the first embodiment. In the process of writing to the monitor memory area 3, the user software first searches for a boundary between already written bits and unwritten bits (S3). Subsequently, based on the search result, a bit to be written is determined according to a fixed predetermined order, and one bit is written into the monitor memory area 3 (S4).

In the process of writing to the monitor memory area 3, for example, one bit is sequentially written from the end of the word line area, and a search is performed in the opposite direction, and the written bits and the unwritten bits are searched. Detect the boundary between bits. FIG. 4 is an explanatory diagram for explaining the writing process to the monitor memory area 3 according to the first embodiment, and shows an example of the writing process at the time of the fifth rewriting after four rewritings. I have. in this case,
As a result of the search, a boundary between the fourth and third bits is detected, and writing is performed on the fourth bit.

As described above, according to the first embodiment,
Since the rewrite frequency information is written in the monitor memory area 3 which is provided separately from the normal flash ROM area 2 and has a high security function until the erase operation is executed, the rewrite frequency is erased due to erroneous writing or the like. It is possible to reduce the possibility and increase the reliability of the rewrite frequency information. Further, the additional writing of the monitor memory area 3 is enabled, the boundary between the written bit and the unwritten bit is searched in reverse order, and the bit to be written is sequentially specified. To reduce costs, and
It is possible to prevent the same cell from being rewritten many times, and to improve the reliability of the rewrite number information.

Embodiment 2 The flash ROM according to the second embodiment has basically the same configuration as the flash ROM 1 according to the first embodiment, except that a monitor memory area 10 described later is provided instead of the monitor memory area 3. When rewriting information is recorded in word line units as in the first embodiment, the maximum value depends on the number of bits connected to the word line. , A certain word line area is written each time rewriting is performed, and when all the word line areas are used, 1-bit information is recorded as carry in another word line area, and The used word line area is cleared (erased) so that a large number of rewrites can be recorded in a small area.

FIG. 5 is an explanatory diagram showing a schematic configuration of the monitor memory area 10 according to the second embodiment of the present invention. The monitor memory area 10 according to the second embodiment includes a plurality of word line areas 10a, 10a corresponding to each digit of the number of rewrites.
b to 10c. The monitor memory area 10, like the monitor memory area 3 according to the first embodiment, has a high security function and can additionally write. In this example, since one word line area is 8 bits, the word line areas 10a, 10b to 10c correspond to the respective digits of the octal number.

The operation of the second embodiment in the above configuration will be described with reference to FIGS. FIG. 6 is a flowchart illustrating a flow of a writing process to the monitor memory area 10 according to the second embodiment. Since the operation of the second embodiment is basically the same as that of the first embodiment, the same parts as those of FIG.
The description is omitted. In the process of writing to the monitor memory area 10, the user software first searches the word line area 10a corresponding to the least significant digit for a boundary between already written bits and unwritten bits (S3).

Next, the word line region 10
It is determined whether or not a is completely used, that is, whether or not all are written (S5). If all the data has been written, the word line area 10a is cleared, the 1-bit information is stored as a carry in the word line area 10b corresponding to the upper digit (S6), and the process ends. On the other hand, if not all data has been written,
Then, writing to a is performed (S4), and the process ends.

FIG. 7 is an explanatory diagram for explaining the writing process to the monitor memory area 10 according to the second embodiment, and shows an example in the case of the ninth rewrite after the eight rewrites. In the writing process to the monitor memory area 10, after rewriting eight times, all bits in the word line area 10a have been written. Therefore, at the time of the ninth rewriting, the word line area 10a is cleared,
One-bit writing is performed in word line region 10b.

As described above, according to the second embodiment,
The monitor memory area 10 is composed of a plurality of word line areas corresponding to each digit of the number of rewrites. When a carry occurs, the word line area corresponding to the lower digit is cleared and the word line area corresponding to the upper digit is cleared. Since one bit is written in the area, the memory area for storing the number of times of rewriting can be further reduced, and the cost can be reduced. In the monitor memory area 10, the normal flash ROM area 2 in which rewriting is performed is rewritten only once less than the number of bits connected to one word line. Is improved.

Embodiment 3 The flash ROM according to the third embodiment has the same configuration as the flash ROM 1 according to the first embodiment, except that a monitor memory area 22 described later is provided instead of the monitor memory area 3. FIG. 8 is an explanatory diagram illustrating a schematic configuration of the flash ROM according to the third embodiment of the present invention. The flash ROM according to the third embodiment includes a sub memory area 20, a main memory area 21,
And a monitor memory area 22 composed of one block. The monitor memory area 22, like the monitor memory area 3, has a high security function and can additionally write.

Here, for example, when the rewriting of the sub memory area 20 is extremely large, for example,
By arranging the monitor memory area 22 inside the block, it is possible to monitor the number of times of rewriting with high reliability by recording in a block with a small number of times of rewriting. In this case, there is no need to specify a word line.

The operation of the third embodiment having the above configuration will be described with reference to FIG. FIG. 9 is an explanatory diagram for explaining a writing process to the monitor memory area 22 according to the third embodiment. Also in the write processing to the monitor memory area 22 according to the third embodiment, as in the first embodiment, the write order is fixed and the bit search at the time of rewriting is performed in the reverse order, so that the memory amount of the monitor memory area 22 is reduced. Can be reduced.

As described above, according to the third embodiment,
One block can be used as a monitor memory area, and the possibility of erasing the number of rewrites due to erroneous writing or the like in this block can be reduced, and the reliability of the number of rewrites information can be increased.

Embodiment 4 The flash ROM according to the fourth embodiment has the same configuration as the flash ROM 1 according to the first embodiment described above, and is provided with a monitor memory area 30 described later instead of the monitor memory area 3. FIG.
Is the monitor memory area 3 according to the fourth embodiment of the present invention.
FIG. 4 is an explanatory diagram showing a schematic configuration of a zero. The monitor memory area 30 according to the fourth embodiment includes the normal flash ROM area 2
And monitor memory areas 31, 32 to 33 for storing the number of times of rewriting for each block for which rewriting is permitted. In addition, the security function is high and additional writing is possible.

The monitor memory areas 31, 32 to 33 may be composed of one word line area as in the case of the monitor memory area 3 according to the first embodiment, or may be constituted by a monitor memory area according to the second embodiment. As in the case of 10, it may be composed of a plurality of word line regions corresponding to each digit of the number of rewrites. Further, the monitor memory area 30 may be a single block, similarly to the monitor memory area 22 according to the third embodiment. If rewritten, the user software performs the same processing as in the first to third embodiments, and updates the number of rewrites in the monitor memory area corresponding to the rewritten block.

As described above, according to the fourth embodiment,
Since the number of rewrites for each block of the normal flash ROM area 2 for which rewriting is permitted is stored, the number of rewrites can be managed for each block.

Embodiment 5 FIG. FIG. 11 is a block diagram illustrating a schematic configuration of the flash ROM according to the fifth embodiment of the present invention. Since the flash ROM according to the fifth embodiment has basically the same configuration as the flash ROM according to the first embodiment, the same portions are denoted by the same reference numerals and description thereof will be omitted. . The flash ROM 41 according to the fifth embodiment includes a normal flash ROM area 2,
A monitor memory area 3, a control unit 42 for controlling the flash ROM 41, and a data address bus 5 are provided.

The control unit 42 also controls the monitor memory area 3
Number updating unit 44 for controlling the writing process to the
An alarm unit 43 is provided to output an alarm signal indicating that the number of times of rewriting has exceeded a predetermined number of times. Note that the monitor memory area 10 according to the second embodiment may be used instead of the monitor memory area 3,
The monitor memory area 22 according to the third embodiment may be used, or the monitor memory area 30 according to the fourth embodiment may be used.

In the above configuration, the operation of the fifth embodiment will be described. Note that the operation of the fifth embodiment is basically the same as that of the first to fourth embodiments, and therefore only different parts will be described. The number-of-times updating unit 44 is different from the first embodiment.
In the flash ROM 41, the writing process to the monitor memory area 3 which was performed by the user software in the steps 4 to 4 is performed. In other words, in the flash ROM 41, the writing process to the monitor memory area 3 is not performed by the user software, but the number updating unit 44 in the flash ROM 41 performs the same processing as in the first to fourth embodiments. 3 is written.

As a result, it is not necessary for the user software to perform the writing process to the monitor memory area 3, and the burden on the user and the user software can be reduced. In addition, it is possible to prevent erroneous writing due to a user's programming error or the like, and to improve the reliability of the rewrite frequency information.

The alarm unit 43 determines whether or not the number of rewrites stored in the monitor memory area 3 exceeds a specified number such as the guaranteed number of rewrites of the flash ROM 41. When the number of rewrites exceeds the guaranteed number of rewrites, an alarm signal such as an interrupt to an external CPU (not shown) is output. This informs the user that the number of rewrites has exceeded the guaranteed number of rewrites,
It can encourage programmatic measures. The determination as to whether or not the number of times of rewriting has exceeded the specified number of times may be made, for example, when searching for a boundary between a written bit and an unwritten bit.

As described above, according to the fifth embodiment,
In addition to the same effects as those of the first to fourth embodiments, the load of the user and the user software can be reduced because the number updating unit 44 performs the writing process to the monitor memory area 3 instead of the user software. In addition, the reliability of the rewrite frequency information can be improved. Further, the alarm unit 43 determines whether the specified number of times such as the guaranteed number of rewrites of the flash ROM 41 has been exceeded, and informs the user that the number of rewrites has exceeded the guaranteed number of rewrites. It is possible to reduce the possibility that the number of times of rewriting will exceed the guaranteed number of times before that and an unexpected error occurs.

[0058]

As described above, according to the present invention, the storage means is provided separately from the ordinary storage means normally used.
The number-of-times storage unit having a high security function stores the number of times of rewriting of the normal storage unit. Thus, the possibility that the rewrite frequency information (information indicating the rewrite frequency) is lost due to erroneous writing or the like can be reduced, so that the reliability of the rewrite frequency information can be improved.

According to the next invention, the number-of-times storage means provided separately from the normally used normal storage means and having no erasing function by the user stores the number of times of rewriting of the normal storage means. Thus, the possibility that the rewrite frequency information is lost due to erroneous writing or the like can be reduced, so that the reliability of the rewrite frequency information can be improved.

According to the next invention, additional writing to the number-of-times storage means is possible, and writing can be performed for each bit instead of for each writing unit. Therefore, the memory area for storing the number of times of rewriting can be reduced. The effect that cost can be reduced is produced.

According to the next invention, instead of the user software, the control means updates the number of rewrites stored in the number storage means provided separately from the normal storage means normally used. This eliminates the need for user software to implement the function of updating the number of rewrites,
In addition, since it is possible to prevent a program error and reduce the possibility of losing the number of times of rewriting due to erroneous writing or the like, the load on the user and the user software is reduced,
In addition, there is an effect that the reliability of the rewrite frequency information can be improved.

According to the next invention, additional writing to the number-of-times storage means is possible, and the control means sets the number of times of the number-of-times storage means every time the data storage means is rewritten.
A bit to be written is determined by searching for a boundary between a written bit and a non-written bit, and one bit is sequentially written. As a result, since writing can be performed not for each writing unit but for each bit, there is an effect that the memory area for storing the number of times of rewriting can be reduced and the cost can be reduced.

According to the next invention, when the number-of-times storage means is one block, the possibility that the number-of-times-of-rewriting information is lost due to erroneous writing or the like can be reduced. Also in this case, there is an effect that the reliability of the rewrite frequency information can be improved.

According to the next invention, when the number-of-times storage means is one word line area, the possibility that the number-of-times-of-rewrite information is lost due to erroneous writing or the like can be reduced. Even in the case of the word line region, there is an effect that the reliability of the number-of-rewrites information can be improved.

According to the next invention, since the plurality of word line regions correspond to each digit of the number of times of rewriting, the memory area for storing the number of times of rewriting can be further reduced. This has the effect of reducing the cost and reducing the cost.

According to the next invention, the alarm means issues an alarm when the number of rewrites stored in the number-of-times storage means exceeds a preset number. This allows
Since the user can be notified that the number of rewrites has exceeded a preset number such as the number of guaranteed rewrites,
It is possible to reduce the possibility that the number of times of rewriting is exceeded before the user notices and an unexpected error occurs.

According to the next invention, the number-of-times storage means can store the number of times of rewriting for each block of the normal storage means for which rewriting is permitted, and can manage the number of times of rewriting for each block. , It is possible to improve the reliability of the rewrite frequency information of each block,
This has the effect.

According to the next invention, every time the flash memory is rewritten, the boundary between the written bit and the unwritten bit in the count storage means is searched to determine the write bit. 1-bit writing to the number-of-times storage means is performed. As a result, since writing can be performed not for each writing unit but for each bit, there is an effect that the memory area for storing the number of times of rewriting can be reduced and the cost can be reduced.

According to the next invention, a plurality of word line areas are assigned to each digit of the number of rewrites,
To clear the word line area corresponding to the lower digit and write one bit to the word line area corresponding to the upper digit,
Further, the memory area for storing the number of times of rewriting can be reduced, and the memory area for storing the number of times of rewriting can be reduced, so that the cost can be reduced.

According to the next invention, since the computer executes the method according to the invention described above, the memory area for storing the number of times of rewriting can be reduced and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a flash ROM (flash memory) according to a first embodiment of the present invention;

FIG. 2 is a flowchart showing a flow of a rewriting operation by user software according to the first exemplary embodiment;

FIG. 3 is a flowchart illustrating a flow of a writing process to a monitor memory area according to the first embodiment;

FIG. 4 is an explanatory diagram for explaining a writing process to a monitor memory area according to the first embodiment;

FIG. 5 is an explanatory diagram illustrating a schematic configuration of a monitor memory area according to a second embodiment of the present invention;

FIG. 6 is a flowchart illustrating a flow of a writing process to a monitor memory area according to the second embodiment;

FIG. 7 is an explanatory diagram for explaining a writing process to a monitor memory area according to the second embodiment;

FIG. 8 is an explanatory diagram illustrating a schematic configuration of a flash ROM according to a third embodiment of the present invention.

FIG. 9 is an explanatory diagram for explaining a writing process to a monitor memory area according to the third embodiment;

FIG. 10 is an explanatory diagram illustrating a schematic configuration of a monitor memory area according to a fourth embodiment of the present invention;

FIG. 11 is a block diagram showing a schematic configuration of a flash ROM according to a fifth embodiment of the present invention.

FIG. 12 is an explanatory diagram showing a schematic configuration of a conventional flash memory.

[Explanation of symbols]

1,41 flash ROM, 2 normal flash ROM area, 3,10,22,30 monitor memory area, 4
42 control section, 5 data / address bus, 43 alarm section, 20 sub memory area, 21 main memory area, 44 number update section.

Claims (13)

[Claims] 1. A normal storage means for storing various data,
It is provided separately from the normal storage means, stores the number of rewrites of the normal storage means, and has a security function until the execution of an erasing operation is performed more frequently than the normal storage means. Flash memory. 2. A normal storage means for storing various data, and a number storage means provided separately from the normal storage means for storing the number of rewrites of the normal storage means and having no erasing function by a user. A flash memory, comprising: 3. The flash memory according to claim 1, wherein said number storage means is capable of additional writing. 4. A normal storage unit for storing various data, a number storage unit for storing the number of rewrites of the normal storage unit, and a rewrite stored in the number storage unit when the normal storage unit is rewritten. A flash memory comprising: control means for updating the number of times. 5. The number-of-times storage means is capable of additional writing, and the control means is configured such that each time the data storage means is rewritten, the written bits of the number-of-times storage means are not written. 5. The flash memory according to claim 4, wherein a boundary with a bit is searched, and one bit is written to said number storage means in a predetermined order. 6. The flash memory according to claim 1, wherein said number storage means is one block. 7. The flash memory according to claim 1, wherein said number storage means is one word line area. 8. The memory according to claim 1, wherein said number storage means is a plurality of word line areas, and each word line area corresponds to each digit of said number of times of rewriting. Flash memory according to one of the above. 9. The apparatus according to claim 1, further comprising an alarm unit for issuing an alarm when the number of rewrites stored in said number storage unit exceeds a preset number. Flash memory according to one of the above. 10. The apparatus according to claim 1, wherein the number-of-times storage means stores the number of times of rewriting for each block of the normal storage means for which rewriting is permitted. Flash memory. 11. A flash memory rewrite frequency storage method for storing a rewrite frequency in a flash memory provided with a frequency storage means for storing a rewrite frequency, wherein each time the flash memory is rewritten,
A search step of searching for a boundary between a written bit and a non-written bit in the count storage means; and writing a 1-bit into the count storage means in a predetermined order based on a search result in the search step. A flash memory rewriting frequency storage method, comprising: 12. The number storage means comprises a plurality of word line areas corresponding to each digit of the number of rewrites, and in the updating step, when a carry occurs, a word line area corresponding to a lower digit is cleared. 12. The flash memory rewrite frequency storage method according to claim 11, wherein one bit is written in a word line area corresponding to an upper digit. 13. A computer-readable recording medium on which a program for causing a computer to execute the method according to claim 11 or 12 is recorded.