JPH11144478A - Information storage method of nonvolatile semiconductor memory and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the information storage method of a nonvolatile semiconductor memory by which the number of re-writings of the nonvolatile semiconductor memory can be increased practically. SOLUTION: The information storage method of a nonvolatile semiconductor memory which has a plurality of storage areas and is provided in an electronic apparatus includes a control counter. The storage area 40 of the nonvolatile semiconductor memory is selected in accordance with the count value of the control counter and information is stored in the selected storage area 40. The count value 41 is added every time when information is stored in the storage area 40 of the nonvolatile semiconductor memory.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for storing information in a nonvolatile semiconductor memory and an electronic apparatus, and more particularly, to a method for storing information in a nonvolatile semiconductor memory.
The present invention relates to a method of storing information in a flash memory in which information is stored in an S-DOS FAT format, and an electronic apparatus including the flash memory.

[0002]

2. Description of the Related Art In an electronic device such as an information processing device or an information storage / reproduction device capable of storing / reproducing information, a nonvolatile semiconductor memory is used as a storage device for storing information (data) at a time when a power supply is turned off. Is used. For example, in a digital still camera that stores image data of a still image (hereinafter, simply referred to as a still image), a flash memory is used as a nonvolatile semiconductor memory that stores the still image.

In this digital still camera, when performing a shooting / storage operation, first, a still image is taken, and the taken still image is converted into a form that can be taken as a file.
The obtained data is stored in the flash memory as permanent data.

[0004] The stored data is stored according to an internal format, for example, the MS-DOS FAT format. FIG. 3 shows the MS-DOS FAT.
Indicates the file format of the format format. In the figure, reference numeral 20 denotes a data information section in which actual data is stored; 21, a directory section for managing file names and times; and 22, an F for managing the use status of the data information section 20.
It is an AT (File Allocation Table) section.

[0005] Here, the ratio of the size of the FAT section 22 and the directory section 21 to the whole size is determined by the data information section 2.
It is determined by the magnitude of zero. The FAT unit 22 stores the size of the file, a pointer to the file stored in the data information unit 20, and the like. This FAT part 2
2 has two areas for security and is always updated with the same information because it relates to the availability of the data information section 20. Therefore, when updating the contents, it is necessary to update both areas of the FAT unit 22 at the same timing. As described above, since the FAT unit 22 has a close relationship with the data information unit 20, the FAT unit 22 is always updated when its free information is changed, for example, by writing to the data information unit 20.

[0006]

Normally, in the case of a flash memory, the unit of reading / writing is divided into a certain unit of byte called a sector.
However, in order to perform writing to each sector, it is necessary to perform an erasing process on a portion called a block in which sectors to be written are grouped in advance. Generally, this sector / block ratio is about 1 to 8 sectors per block 1.

In a digital still camera, M
When storing still image data in the flash memory in the S-DOS FAT format, it is necessary to perform writing / reading in block units with a plurality of sectors as one block. Therefore, when an attempt is made to rewrite data in one sector of the flash memory,
It is necessary to perform an erasing process on the entire block to which the sector belongs, and to rewrite the block with the block information including the writing information for the sector. Therefore, when the contents of individual sectors existing in the same block are arbitrarily rewritten, multiple erasing processes are required.

Further, there is a limit to the number of times information can be rewritten in an EEPROM used for a memory portion of a flash memory.
It is about 10,000 times. Therefore, when there is a block in the same flash memory in which writing is complicated, the life of the entire flash memory is determined by the block. MS-DOS FA
When data is stored in the flash memory in the T format, writing to the storage area where the FAT unit 22 is stored is concentrated, so that the life of each block of the flash memory is not uniform, and the life of the entire flash memory is not equal. Is F
There is a problem that the life of the AT unit 22 is determined.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a method of storing information in a nonvolatile semiconductor memory and an electronic apparatus, wherein It is an object of the present invention to provide a technology capable of effectively increasing the value.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0011]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

In a method of storing information in a nonvolatile semiconductor memory in an electronic device including a nonvolatile semiconductor memory provided with a plurality of storage areas, a control counter is provided, and the nonvolatile semiconductor memory is stored in the nonvolatile semiconductor memory based on a count value of the control counter. Selecting a storage area, storing information in the selected storage area, and counting up the count value of the control counter each time information is stored in the storage area of the nonvolatile semiconductor memory. I do.

In an electronic apparatus including a control device and a nonvolatile semiconductor memory provided with a plurality of storage areas, the control device determines information based on a count value from the plurality of storage areas of the nonvolatile semiconductor memory. And a control counter that is incremented by the control device every time information is stored in the storage area of the nonvolatile semiconductor memory.

[0014] The information stored in the plurality of storage areas of the nonvolatile semiconductor memory is management information of information stored in storage areas other than the plurality of storage areas of the nonvolatile semiconductor memory. .

The nonvolatile semiconductor memory is a flash memory.

[0016] The electronic device is a digital still camera.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a digital still camera will be described below in detail with reference to the drawings.

In all the drawings for describing the embodiments, those having the same functions are denoted by the same reference numerals, and their repeated description will be omitted.

FIG. 1 is a block diagram showing a digital audio system according to an embodiment of the present invention.
It is a block diagram which shows schematic structure of the storage circuit system to the non-volatile semiconductor memory in a still camera. In the figure, reference numeral 10 denotes a control unit (MPU) for controlling the entire apparatus including data control, 11 denotes a video input unit for inputting a still image,
Reference numeral 12 denotes a data conversion unit for converting a still image into information to be captured as a file, 13 denotes a buffer memory used when performing various processing such as image compression processing by the data conversion unit 12, and 14 denotes a file memory for storing file data permanently. The nonvolatile semiconductor memory to be held, 15 is a bus line, and 31 is a counter. This nonvolatile semiconductor memory is constituted by a flash memory.

In this digital still camera, when performing a photographing / storing operation, first, a still image is captured by the video input unit 11, and the still image captured by the data conversion unit 12 is converted into a form that can be captured as a file. The stored data is stored in the flash memory 14 as permanent data. In this case, the stored data is MS-DOS.
It is stored according to the FAT format.

The counter 31 has a JQ flip-flop.
A combination of flop circuits is used, and after counting the number of assigned FAT units 22 (eight in the present embodiment), the value is returned to the initial value. The counter 31 is always operated by an internal power supply (not shown).
Power is supplied. The counter 31 may be of any type as long as it can count the number of allocated FAT units 22 and can hold the counted value.

FIG. 2 is a diagram showing an area where the FAT section of the flash memory according to the present embodiment is stored. In the figure, 22 is a FAT unit, 40 is a storage area of the flash memory 14 where the FAT unit 22 is stored, and 41 is a count value of the control counter 31.

Next, a writing method of the nonvolatile semiconductor memory according to the present embodiment will be described with reference to FIGS. 1, an FAT storage area similar to that of the FAT unit 22 is prepared in the buffer memory 13. During the operation of the camera, the FAT storage area of the buffer memory 13 is usually used to reduce the number of times of writing to the FAT unit 22. In addition, as the storage area 40 in the flash memory 14, an area having a size in which a plurality of FAT sections 22 are stored (an area corresponding to a required sector of the FAT section 22 × the number of mutual uses) is prepared. In the present embodiment, as shown in the storage area 40 of FIG.
Are prepared.

As described in the above section, the FAT section 22 is usually provided with two areas. However, in the digital still camera of the present embodiment, one FAT section is provided based on the capacity of the flash memory 14. Since only two sectors were used per 22 and the internal format was set to 8 sectors / block, 2 FAT sections could be accommodated in one block. As a result, a replacement storage area can be prepared in block units. Therefore, a storage area of 8 blocks is prepared for replacement, and each block is sequentially changed and used. If it does not fit,
It is necessary to devise the format and management method,
Since it deviates from the content of the present invention, it is omitted here.

At the time of a new operation, the counter value of the control counter 41 is set to 0, and the FAT unit 22 to be used first is set to the block 0 of the storage area 40. The control unit 10 previously associates each block with the count value 41 of the control counter 31 using a table or the like. In FIG.
For convenience, when the counter value 41 of the control counter 31 is 0, block 0 of the storage area is set. When the counter value 41 is 1, block 1 of the storage area is set. Although the block 7 of the storage area is allocated, this combination may take any form as long as it can be managed.

A write command to the FAT unit 22 from outside,
Alternatively, when the writing process to the FAT storage area in the buffer memory 13 is completed, the control unit 10 increments the value of the control counter 31 by one. Then, the control unit 1
0 reads the count value 41 of the control counter 31;
The block corresponding to the count value 41 in the storage area 40 of the flash memory 14
A process of writing information in the FAT storage area of No. 3 is executed.

In the present embodiment, since the initial value of the control counter 31 is set to 0, 1 is set when counting up. Therefore, the control unit 10 controls the block 1
Is used as a new FAT unit 22, and thereafter, a new FA
This block is used as the current FAT unit 22 until a write process to the T unit 22 occurs. In this case,
The current access to the FAT unit 22 is
This is performed by reading the count value 41 of the control counter 31 and obtaining an address corresponding to the count value 41. Even when the power is turned off, the contents of the control counter 31 are guaranteed because the control counter 31 is backed up by the internal battery. Therefore, it can be reliably referred to even when the power is turned on next time. In the present embodiment, eight blocks are assigned to the FAT unit 2.
Since it has been assigned to 2, the control counter 31 returns to the initial state at the eighth count.

In addition to the present embodiment, for example, the number of times the block has been used (the number of times the FAT unit 22 has been stored) is stored in each block of the storage area 40 of the flash memory 14, and the control unit An information storage method is also conceivable in which the 10 reads out the number of uses stored in each block and writes information to a block with a small number of uses.
However, in this method, the control unit 10 needs to read the number of times of use from each block before executing the writing process of the FAT unit 22 to the storage area 40 of the flash memory 14. It is necessary to store the block in use, and there is a disadvantage that the processing of the control unit 10 is complicated.

However, in the present embodiment, the control counter 31 is provided, and a block for storing the FAT section 22 (eight blocks in the storage area 40 of the flash memory 14) is provided based on the count value 41 of the control counter 31. Of the FAT) and the current FAT
When reading the information of the section 22, the control counter 31
Based on the count value 41, it is only necessary to access at an address corresponding to the count value 41. in this way,
In the present embodiment, the control unit 10 only needs to be aware of the count-up of the control counter 31 and does not need to perform any other control, so that the processing of the control unit 10 can be simplified. In the above description, the control unit 10
After incrementing the value of the control counter 31 by one, the count value 41 of the control counter 31 is read, and information is written in a block corresponding to the count value 41. However, the present invention is not limited to this. Part 10
May read the count value 41 of the control counter 31, write information to a block corresponding to the count value 41, and then increment the value of the control counter 31 by one. However, in this case, when reading the current information of the FAT unit 22, it is necessary to access at an address corresponding to a count value obtained by subtracting 1 from the count value 41 of the control counter 31.

As described above, in the present embodiment,
Number of times of writing to the FAT unit 22 (number of times of data update processing)
Can be reduced to 1/8 of the conventional example.
That is, in the present embodiment, the number of times of writing to the FAT unit 22 can be effectively increased eight times as compared with the conventional example, thereby effectively increasing the life of the FAT unit 22 by eight times. It becomes possible. Further, the life of each block of the flash memory 14 can be equalized, and the life of the entire flash memory 14 can be increased (life prolonged).

In this embodiment, since the FAT unit 22 is allocated to only two sectors, there is no variation in the life between the FAT units 22 by managing the same block.
When the area of the FAT unit 22 extends over a plurality of blocks,
In some cases, the life of the FAT unit 22 varies.
Even in such a case, by applying the present embodiment a plurality of times, it is possible to perform adjustment in smaller units. However, the spare area of the flash memory 14 (storage area 4
In order to secure (0), it is necessary to reduce the data information area 20 by that amount. Therefore, it is necessary to determine how much storage area 40 to secure according to the use environment.

In the above embodiment, the case where the present invention is applied to a digital still camera has been described. However, the present invention is not limited to this. For example, the present invention has an equivalent function of storing a still image, It goes without saying that the present invention can be applied to general electronic equipment such as an information storage / reproduction device having a flash memory.

In any case, the present embodiment uses the FAT
A method of distributing the number of updates of the FAT unit 22 stored in the flash memory 14 by storing the unit 22 in a plurality of areas and sequentially using the plurality of areas.
The number of storage areas 40 and the format configuration etc.
The present embodiment may be applied as far as it can be realized, depending on the configuration conditions of each electronic device and the size of the flash memory to be used.

As described above, the invention made by the present inventor is:
Although a specific description has been given based on the above-described embodiment, the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the invention.

[0035]

The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows.

(1) According to the present invention, a plurality of storage areas are provided in a nonvolatile semiconductor memory, and when storing information in the nonvolatile semiconductor memory, the plurality of storage areas are sequentially changed and used. , It is possible to effectively increase the number of storage times of the nonvolatile semiconductor memory,
It is possible to increase the life of the nonvolatile semiconductor memory.

(2) According to the present invention, a control counter which counts up each time information is stored in each storage area is provided, and the storage area is selected based on the count value of the control counter. Since the inside storage area is accessed, the processing of the control unit can be simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a storage circuit system for a nonvolatile semiconductor memory in a digital still camera according to an embodiment of the present invention.

FIG. 2 is a diagram showing an area where a FAT section of the flash memory according to the embodiment is stored.

FIG. 3 is a diagram showing a file format of an MS-DOS FAT format.

[Explanation of symbols]

10: control unit (MPU), 11: video input unit, 12: data conversion unit, 13: buffer memory, 14: nonvolatile semiconductor memory (flash memory), 15: bus line,
20: data information section, 21: directory section, 22: F
AT unit, 31 counter, 40 storage area, 41 count value of control counter 31.

Claims (8)

[Claims] 1. An information storage method for a nonvolatile semiconductor memory in an electronic device including a nonvolatile semiconductor memory provided with a plurality of storage areas, comprising: a control counter; and a nonvolatile semiconductor memory based on a count value of the control counter. Selecting a storage area of the memory, storing information in the selected storage area, and counting up the count value of the control counter each time information is stored in the storage area of the nonvolatile semiconductor memory. A method for storing information in a nonvolatile semiconductor memory. 2. The information stored in a plurality of storage areas of the nonvolatile semiconductor memory is management information of information stored in a storage area other than the plurality of storage areas of the nonvolatile semiconductor memory. 2. The information storage method for a nonvolatile semiconductor memory according to claim 1, wherein: 3. The information storage method for a nonvolatile semiconductor memory according to claim 1, wherein said nonvolatile semiconductor memory is a flash memory. 4. The electronic device according to claim 1, wherein the electronic device is a digital still
4. The camera according to claim 1, wherein the camera is a camera.
An information storage method for a nonvolatile semiconductor memory according to any one of the above items. 5. An electronic device, comprising: a control device; and a nonvolatile semiconductor memory provided with a plurality of storage areas, wherein the control device selects one of the plurality of storage areas of the nonvolatile semiconductor memory based on a count value of the control device. An electronic device comprising: a control counter that selects a storage area for storing information and that is incremented by the control device each time information is stored in the storage area of the nonvolatile semiconductor memory. 6. The information stored in a plurality of storage areas of the nonvolatile semiconductor memory is management information of information stored in a storage area other than the plurality of storage areas of the nonvolatile semiconductor memory. The electronic device according to claim 5, wherein 7. The electronic device according to claim 5, wherein the nonvolatile semiconductor memory is a flash memory. 8. The electronic device according to claim 1, wherein the electronic device is a digital still device.
8. A camera according to claim 5, wherein the camera is a camera.
An electronic device according to any one of the preceding claims.