JPH10289144A - Memory control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extend the service life of a flash memory by using first a sector that remains longest as a free area in terms of a time series when the free area is secured for writing the data. SOLUTION: When the accesses are given to a storage 10 for the writing, erasion, etc., of files, a memory controller 102 controls a flash memory 101. In a file write mode, the FAT entries showing successively the idle sectors at and after the head of a FAT area are retrieved and the files are written into the sectors which are shown by the retrieved FAT entries. At the same time, the retrieved FAT entries are rewritten into the FAT entries showing the non-idle sectors. In a file erasion mode, the relevant file is deleted and also a new FAT entry is produced for the sector that becomes idle use to the file deletion. Then the new FAT entry is recorded at the end of the FAT area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for controlling a memory.

[0002]

2. Description of the Related Art An information processing apparatus such as a personal computer has a RAM used in a program execution process.
In addition to (random access memory), a storage device for storing various application software is provided. As this type of storage device, it is necessary to retain the stored content even after power is turned off, and a hard disk device using a magnetic recording disk has been employed as the storage medium.

[0003] In recent years, however, attempts have been made to use a writable non-volatile semiconductor memory such as a flash memory in place of the magnetic recording disk with the high-speed access of the storage device. Flash memory applies a high voltage to the gate region of its memory cell,
Data is written and stored by forming charges in such a gate region.

[0004] However, the flash memory has a problem that if the above-mentioned writing is concentrated on one memory cell, the characteristics of the semiconductor itself are deteriorated and the memory cell is destroyed.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in order to solve such a problem, and an object of the present invention is to provide a method of controlling a memory which can extend the service life of the memory.

[0006]

According to a memory control method of the present invention, a memory recording area is divided into a plurality of sectors each having a predetermined recording capacity, and the memory is controlled on a sector-by-sector basis. A fat entry indicating whether or not each of the sectors is a free sector is recorded in a fat area of the memory, and at the time of writing a file, the sectors are sequentially free sectors from the head of the fat area. A fat entry indicating that the file is written to the sector indicated by the search fat entry, and the search fat entry is rewritten to a fat entry indicating that the sector is not a free sector. Was deleted, and the file was deleted and became a free sector. And create a new fat entry for Kuta wherein the record this to the end of the fat region.

[0007]

FIG. 1 is a diagram showing an example of the configuration of an information processing apparatus. In FIG. 1, a storage device 10 includes a writable flash memory 101 capable of retaining its stored contents even after power is turned off, and a memory controller 102 that performs writing and reading control on the flash memory 101. Consists of

FIG. 2 is a diagram showing an initial logical format of the flash memory 101. As shown in FIG. 2, the flash memory 101 is in its initial state.
Storage areas are hook area, directory area, FSL
(Free Storage List) _FAT area and file area. The access to the flash memory 101 is performed by using unique SIDs.
(Sector ID) It is implemented in units of sectors indicated by 0 to N, and the hook area is allocated to the sector of SID = 0 at the time of the initial logical format.

In the following description, it is assumed that all bits of the flash memory 101 have a logical value "0" when initialized or data is erased. It is assumed that data can be erased only in block units, but writing to erase bits ("0" → "1") can be performed in word units (predetermined number of bits). FIG. 3 is a diagram showing a memory format at the time of the initial logical format of the hook area.

In FIG. 3, at the head of the hook area, an identification ID indicating that this one sector is a hook area, and a sector check indicating whether the sector allocated to this hook area is normal or not. The byte CB is recorded. Further, the first sector I of the directory area
A D-SID indicating D is recorded, and thereafter, an additional recording area is arranged. When the D-SID is updated to a new one, the additional D-SID is updated to the latest D-SID.
Are sequentially added.

In this embodiment, it is assumed that a sector ID in which a hook area exists is written in the identification ID, and a value obtained by inverting all bits of the identification ID is written in CB.
FIG. 4 is a diagram showing a memory format in the initial logical format of the directory area shown in FIG. As shown in FIG. 4, the directory area contains F
SL directory entries 0 to n and directory entries 0 to k are formed.

[0012] Each of the FSL directory entries 0 to n has a delete check byte DCB indicating whether or not this FSL directory entry is valid, a file type, and a valid FAT present at the foremost position in the FSL_FAT area. FT-S as a sector ID indicating a sector in which an entry (described later) is recorded
The ID is recorded. At the time of the initial logical format and after the data has been erased, all the bits of the delete check byte DCB of each of the FSL directory entries 0 to n have the logical value “0” indicating “valid”. ing. In other words, it becomes "valid" when no data is written after erasure or initialization.

On the other hand, in each of the directory entries 0 to k, a delete check byte DCB indicating whether or not this directory entry is valid, file information (file information) on the file written in the file area of FIG. Name, file size, file type, recording date and time) and FL-
The SID is recorded. Incidentally, at the time of the initial logical format and after the data is erased, directory entries 0 to 0 are set.
All bits of each k of the delete check bytes DCB have a logical value "0" indicating "valid".
In other words, it becomes "valid" when no data has been written after initialization or data erasure.

At the head of the directory area, an nSID indicating the connection information of the sectors in this area is recorded. At this time, every time the entire recording capacity exceeds one sector, as shown in FIG. 4, an nSID as sector connection information is recorded at the head of each sector as shown in FIG. still,
The FSL directory entry and the file type in the directory entry are the attributes of the file or subdirectory indicated by the directory entry,
And information indicating whether the entry is an FSL directory entry or a directory entry.

For example, if the destination pointed to by a directory entry is a write-protected subdirectory, its attributes and information indicating that this entry is a directory entry are written as a file type. Therefore, in the description of FIG. 4, the directory area is clearly divided into the FSL directory entry and the directory entry. However, when actually used, the type of each entry is more attributed than the fill type recorded in the entry. You can know. That is, the FSL directory entry and the area of each directory entry need not be clearly divided. In this case, even if the FSL directory entry and the directory entry are not clearly divided in the directory area, the connection destination of each sector can be known by each nSID.

FIG. 5 is a diagram showing a memory format in the initial logical format of the FSL_FAT area shown in FIG. In the FSL_FAT area, a fat pointer FP indicating each sector ID in a free area (a set of writable sectors) existing in the flash memory 101, and whether or not the sector indicated by the fat pointer FP is an empty sector A FAT entry consisting of a delete check byte DCB is formed. Such FAT entries are provided corresponding to all sectors in the free area of the flash memory 101. At this time, the above-mentioned delete check byte DC
If all the bits of B are logical values “0” indicating that the sector is a free sector, this FAT entry is a “valid” FA
Let it be a T entry. Also, at the head of the FSL_FAT area, an nSID indicating connection information of sectors in this area is recorded. When the capacity of all FAT entries exceeds the capacity of one sector, as shown in FIG. 5, an nSID as sector connection information is recorded at the head of each sector as shown in FIG. The nSID indicates the SID of the sector connected to the next sector.

Even if the above-mentioned areas (directory area, FSL_FAT area, file area) are not arranged continuously, the sector to be connected next can be known from the nSID of each sector. That is, it can be treated as a logically continuous area. In the file area of the flash memory 101 as described above,
Various application programs and information files are stored. Further, in the file area of the flash memory 101, an operating system (hereinafter, referred to as OS) program to which the memory control method according to the present invention is applied is stored in advance.

When the power is turned on, the OS program is
RAM read from such flash memory 101
(Random access memory) 12 is written in a predetermined area. When the user operates the operation device 13 to execute any one of the application programs, the program is read from the flash memory 101 and read into the RAM 12. The CPU (Central Processing Unit) 11 executes the application program read on the RAM 12 and displays the execution result on the display 14.

At this time, when an access such as writing or erasing of a file to the storage device 10 occurs due to execution of the application software, the memory controller 102 controls the flash memory 101 to perform control processing according to the OS. Run. The following describes writing, erasing, and writing of a new file performed by executing the OS program.
Each operation of updating and updating will be described by taking a flash memory 101 having an initial logical format as shown in FIG. 6 as an example.

The file area shown in FIG. 6 has a total capacity of 20 Kbytes and is composed of ten sectors each having a capacity of 2 Kbytes. At this time, each sector is indicated by sector IDs: Q to (Q + 9). or,
In the fat pointer FP of each of the FAT entries 0 to 9, sector IDs: Q to (Q + 9) corresponding to the sectors in the file area are recorded. The delete check byte DCB of each of the FAT entries 0 to 9 has a logical value "0" indicating that the sector indicated by the fat pointer FP is a free sector, that is, a write-enabled sector. At this time, FAT entries 0 to 5
Is recorded in the sector indicated by the sector ID: R,
The FAT entries 6 to 9 are recorded in the sector indicated by the sector ID: (R + 1).

Accordingly, the sector ID: R of the sector in which the FAT entry 0 exists is recorded as the FT-SID of the FSL directory entry 0. The delete check byte DCB of the FSL directory entry 0 is:
The logical value "0" indicates that the FSL directory entry 0 is valid. Hereinafter, from the state as shown in FIG. 6, five new files A to E each having a capacity of 4 Kbytes are sequentially written, and after erasing the written files in the order of files C, E, and A,
An operation example until a file F having a new capacity of 6 Kbytes is written will be described with reference to FIGS.

Writing of files A to E In the state shown in FIG. 6, first, the memory controller 102 stores the D- file in the hook area shown in FIG.
Read the SID. The memory controller 102 recognizes the leading sector ID of the directory area based on the contents of the read D-SID, and identifies the valid (the logical value of the DCB is "0") FS in the leading position in this sector.
Search for L directory entry. At this time, as shown in FIG. 6, the valid FSL directory entry existing at the top position is FSL directory entry 0.
It is. In the sector indicated by the sector ID: R recorded as the FT-SID of the FSL directory entry 0, the memory controller 102 determines the valid FAT entry (the logical value of the DCB of which is "0") at the foremost position. FAT entry). At this time, the valid FAT entry existing at the foremost position in the sector indicated by the sector ID: R is the FAT entry 0 as shown in FIG. Here, as shown in FIG. 7, the memory controller 102 writes the file A to the sector indicated by the sector ID: Q recorded as the fat pointer FP of the FAT entry 0. At this time, file A
Has a capacity of 4 Kbytes, which is larger than the capacity of one sector (2 Kbytes). Therefore, the memory controller 10
2 is a valid FA existing next to the FAT entry 0
Search for a T entry. At this time, the searched FAT entry is the FAT entry 1 as shown in FIG. Here, the memory controller 102
In the sector indicated by the sector ID: (Q + 1) recorded as the fat pointer FP of the entry 1, FIG.
Then, the continuation of the file A is written as shown in FIG.

FIG. 14 is a diagram showing a format at the time of writing the file A. As shown in FIG.
In the sector indicated by the sector ID: Q, the first half of the file A is written, and (Q + 1) is recorded at the head position as nSID indicating the connection information of the next sector. The latter half of the file A is written in the sector indicated by (Q + 1). Nothing is written in the nSID indicating the connection information of the next sector at the head position, and the value is left as “0”. This indicates that there is no connection to the next sector.

Further, new appending to the file A can be performed by writing a newly added sector ID to the nSID of the last sector of the file A. Next, the memory controller 102 rewrites the logical values of the DCBs of the FAT entries 0 and 1 to “1” as shown in FIG. 7 so that the sectors indicated by the sector IDs: Q and (Q + 1) Indicates that writing has become invalid. Next, the memory controller 102 searches the directory area for the head of a directory entry that has not been written. At this time, the first directory entry which has not been written in the initial state as described above is the directory entry 0 as shown in FIG. Here, the memory controller 102
Stores the file A in the directory entry 0
File information (file name, file size,
File type, recording date and time), and the first sector ID: Q on the flash memory 101 in which the file A is written.

Through a series of operations as described above, the memory controller 102 completes the operation of writing the file A.
The memory controller 102 sequentially writes the file B and the file C by a method similar to the writing operation of the file A. FIG. 8 is a diagram showing a state of the flash memory 101 when writing of each of the files A, B, and C is completed.

As shown in FIG. 8, sector IDs: Q to
Each sector indicated by (Q + 5) is a file A
To C are used. Therefore, these sectors I
D: All the logical values of the delete check byte DCB of each of the FAT entries 0 to 5 indicating Q to (Q + 5) become “1”. Therefore, as shown in FIG. 8, no valid FAT entry exists in the sector indicated by the sector ID: R. At this time, the FAT entry existing at the foremost position in the FSL_FAT area and valid is shown in FIG.
Is the FAT entry 6 as shown in FIG.
The sector ID of the sector in which entry 6 is recorded is (R +
1). Therefore, the memory controller 102
Unrecorded in the SL directory entry,
Further, the FSL directory entry existing at the top is searched. As shown in FIG. 8, the FS which is not recorded in the FSL directory entry and which is present at the top
Since the L directory entry is the FSL directory entry 1, the memory controller 102
The above (R + 1) is recorded as the FT-SID of the SL directory entry 1.

Further, the DCB is set to "1" in order to make the directory entry 0 which has been "valid" up to now "invalid". In writing the file D as the next new file in the state shown in FIG. 8, first, the memory controller 102 reads out the D-SID in the hook area shown in FIG. Memory controller 1
No. 02 recognizes the first sector ID of the directory area based on the contents of the read D-SID, and searches for a valid (DCB logical value “0”) FSL directory entry at the first position in this sector. . At this time, as shown in FIG. 8, the valid FSL directory entry existing at the head position is the FSL directory entry 1. The memory controller 102
In the sector indicated by the sector ID: (R + 1) recorded as the FT-SID of the FSL directory entry 1, the valid (D
The FAT entry whose logical value of CB is “0”) is searched. At this time, the valid FAT entry existing at the foremost position in the sector indicated by the sector ID: (R + 1) is the FAT entry 6 as shown in FIG. Here, the memory controller 102
In the sector indicated by the sector ID: (Q + 6) recorded as the fat pointer FP of the entry 6, FIG.
The file D is written as shown in FIG. At this time, the capacity of the file D is 4 Kbytes, which is larger than the capacity of one sector (2 Kbytes). Therefore, the memory controller 102 searches for a valid FAT entry existing next to the FAT entry 6. At this time, the FAT entry to be searched is, as shown in FIG.
Entry 7 Here, the memory controller 102
Writes the continuation of the file D into the sector indicated by the sector ID (Q + 7) recorded as the fat pointer FP of the FAT entry 7 as shown in FIG.

Next, the memory controller 102 rewrites the logical value of the DCB of the FAT entries 6 and 7 to "1" as shown in FIG.
D: Indicates that writing to each of the sectors indicated by (Q + 6) and (Q + 7) has become invalid. Next, the memory controller 102 searches the directory area for the head of a directory entry that has not been written. At this time, the first directory entry that has not been written in the state as shown in FIG. 8 is the directory entry 3. Here, as shown in FIG. 9, the memory controller 102 writes the file information (file name, file size, file type, recording date, etc.) regarding the file D and the file D in the directory entry 3. ID of the first sector on the flash memory 101 that has been inserted:
Record (Q + 6).

Through a series of operations as described above, the memory controller 102 completes the operation of writing the file D.
In a similar manner, the memory controller 102 writes the file E. FIG. 10 shows the file A,
FIG. 9 is a diagram showing a state of the flash memory 101 when writing of each of B, C, D, and E is completed.

In deleting the files C in the state shown in FIG. 10, the memory controller 102 firstly deletes the files C, E, and A.
A search is made for a directory entry in which the file C is recorded as a file name from the directory entry. At this time, the directory entry is the directory entry 2 as shown in FIG. Here, the memory controller 102 indicates the sector ID: (Q + 4) recorded as the FL-SID of the directory entry 2 and the sector ID to be connected next (Q + 5) recorded in the nSID of this sector. Erase the written contents of each sector to be written. By such an operation, the file C written in the file area is erased as shown in FIG.

Next, the memory controller 102 rewrites the logical value of the DCB of the directory entry 2 to "1" as shown in FIG. As a result, the recorded contents of the directory entry 2 become invalid. Next, the memory controller 102 sets the FSL_FAT
The end of the written FAT entry is searched in the area. In the state as shown in FIG. 10, the last of the written FAT entry is the FAT entry 9. Here, the memory controller 102 checks the FAT entries 10 and 11 next to the FAT entry 9.
As shown in FIG. 11, (Q + 4) and (Q + 5) are recorded as each fat pointer FP. That is, by deleting the file C, the file area (Q +
Since (4) and (Q + 5) are new free areas, (Q + 4) and (Q + 5) are created in the FAT entry as valid FAT pointers indicating these. here,
The memory controller 102 reads these FAT entries 1
Nothing is written to the DCB of each of 0 and 11.

Through a series of operations as described above, the memory controller 102 completes the operation of erasing the file C.
In a similar manner, the memory controller 102 erases the files E and A. FIG. 12 is a diagram showing a state of the flash memory 101 when the erasure of these files A, C, and E is completed in the order of C, E, and A.

In writing the file F (6 Kbytes) in the state shown in FIG. 12, when writing the file F having a capacity of 6 Kbytes as a new file, first, the memory controller 102 Is read out. Memory controller 10
2 recognizes the head sector ID of the directory area based on the contents of the read D-SID, and searches for the valid (DCB logical value "0") FSL directory entry at the head position in this sector. . At this time, as shown in FIG. 12, the valid FSL directory entry existing at the foremost position is the FSL directory entry 1. Memory controller 102
Is the FT-SID of this FSL directory entry 1.
In the sector indicated by Sector ID: (R + 1) recorded as (1), a valid (at the DCB logical value “0”) FAT entry existing at the head position is searched. At this time, in the sector indicated by the sector ID: (R + 1), the valid F
The AT entry is a FAT entry 10 as shown in FIG. Here, the memory controller 102
Writes the file F into the sector indicated by the sector ID: (Q + 4) recorded as the fat pointer FP of the FAT entry 10 as shown in FIG. At this time, the capacity of the file F is 6 Kbytes, which is larger than the capacity of one sector (2 Kbytes). Therefore, the memory controller 102
A valid FAT entry existing after the entry 10 is searched. At this time, the searched FAT entry is as shown in FIG.
The FAT entry 11 is as shown in FIG. Here, the memory controller 102 writes the continuation of the file F into the sector indicated by the sector ID: (Q + 5) recorded as the fat pointer FP of the FAT entry 11 as shown in FIG. .
Further, in order to write the remaining portion (2 Kbytes) of the file F, the memory controller 102 searches for a valid FAT entry existing next to the FAT entry 11. At this time, the FAT entry searched for is the FAT entry 12, as shown in FIG. here,
The memory controller 102 stores the FAT entry 12
Sector I recorded as fat pointer FP of
D: The remaining portion (2 Kbytes) of the file F is written in the sector indicated by (Q + 8) as shown in FIG.

FIG. 15 is a diagram showing a format at the time of writing the file F. As shown in FIG.
In the sector indicated by the sector ID: (Q + 4), a part of the file F is written, and the head position thereof is
As the nSID indicating the connection information of the next sector, (Q +
5) is recorded. In the sector indicated by (Q + 5), the continuation of the file F is written,
At the head position, nS indicating connection information of the next sector is displayed.
(Q + 8) is recorded as the ID. The last part of the file F is written in the sector indicated by (Q + 8). Also, nothing is written to the nSID indicating the connection information of the sector at the head position, so that it remains "0". This indicates that there is no connection to the next sector as the file F.

Next, the memory controller 102 transmits the FAT entries 10, 11 and 12 relating to the file F.
The logical value of each DCB is rewritten to "1" as shown in FIG. 13 to indicate that each sector indicated by sector IDs: (Q + 4), (Q + 5) and (Q + 8) has become write-ineffective. Show. Next, the memory controller 102 searches the directory area for the head of a directory entry that has not been written. At this time, FIG.
The first directory entry that has not been written in the state as shown in FIG. 2 is the directory entry 5. Here, the memory controller 102
As shown in FIG. 13, file information (file name, file size, recording date and time, etc.) relating to the file F and the top of the flash memory 101 where the file F is written are stored in the directory entry 5 as shown in FIG. Sector ID: (Q + 4) is recorded.

Here, as shown in FIG. 13, there is no valid FAT entry in the sector indicated by each of the sector IDs: R and (R + 1). At this time, the head of the valid FAT entry in the FSL_FAT area is the FAT entry 13 existing in the sector having the sector ID: (R + 2). Therefore, the memory controller 102 searches the FSL directory entry for an unrecorded and foremost FSL directory entry. As shown in FIG. 13, the FSL directory entry which has not been recorded and is present at the forefront in the FSL directory entry is the FSL directory entry.
SL directory entry 2. Therefore, the memory controller 102 records the above (R + 2) as the FT-SID of the FSL directory entry 2.

As described above, in the memory control method according to the present invention, as shown in FIG. 6, an empty sector (writable sector) in a file area is regarded as a linear list structure, and a pointer of the linear list is used. (Fat pointer F
P) is recorded in the FSL_FAT area. Here, at the time of writing a file, as shown in FIGS. 7 to 10 and 13, empty sectors are sequentially searched from the head position of the FSL_FAT area. Write. After that, the delete check byte DCB in the FAT entry indicating the sector in which this file has been written is rewritten to a logical value "1", that is, a delete check byte indicating that the sector is not an empty sector. 11 and 12 when deleting a file.
As shown in (1), the file to be deleted is deleted, and a new FAT entry for a sector which has become a free sector due to this file deletion is newly created and added to the end of the FSL_FAT area.

When the memory management is performed as described above, when securing a free area for writing data, a sector that is left as the longest free area in time series is used. According to such a control method, when a file is updated, only a specific sector is prevented from being frequently used, so that the life of the flash memory can be extended.

In the memory control method according to the present invention, as shown in FIGS. 3 to 5, 14 and 15, information (nSID) indicating the connection between the sectors in the flash memory is used for each sector. Is recorded at the head position. Therefore, when a file is deleted, if the sector is erased, the information indicating the connection between the sectors is also erased at the same time. It is possible to prevent rewriting from being concentrated on the sector.

When all directory entries in the first sector of the directory area are invalidated by the above-described file writing and erasing operations, or the like, or the additional write area in this directory area becomes a predetermined area. When the capacity is smaller than the capacity, the memory controller 102 optimizes the directory area for the flash memory 101.

The optimization of the directory area by the memory controller 102 will be described below with reference to FIGS. 13 and 16. At this time, FIG. 16A shows an example of a recording state before optimization of a directory area, and FIG. 16B shows an example of a recording state after optimization. FIG.
In the example shown in (a), it is assumed that the directory area before optimization is composed of three sectors indicated by sector IDs: Y to (Y + 2).

Here, in optimizing the state of FIG. 16A, the memory controller 102
First searches for a free sector in the free area of the flash memory 101, and adds this free sector to the last sector as a directory area. For example, in the state of FIG. 13, the memory controller 102 refers to the FAT entries in order to obtain the sector ID: (Q +
It is determined that the sector indicated by 9) is an empty sector,
This sector is added as the last sector of the directory area. That is, the sector ID that was the last sector of the directory area in the state before the optimization: (Y + 2)
(Q + 9) is described as shown in FIG. 16B in the nSID of the sector indicated by. Further, the memory controller 102 sets the DAT of the FAT entry 13 to invalidate the FAT entry 13 shown in FIG.
CB is rewritten to a logical value “1”. By this operation, the sector indicated by the sector ID: (Q + 9) becomes a directory area.

Next, the memory controller 102
As shown in FIG. 16B, all the valid directory entries existing in the sector indicated by the sector ID: Y, which was the first sector of the directory area in the state of FIG. : Copy to sector indicated by (Q + 9). Next, the memory controller 10
2 erases all the information recorded in the sector indicated by the sector ID: Y, and sets the sector indicated by the sector ID: Y to a free area as shown in FIG. And That is, the memory controller 102
Indicates that the sector with sector ID: Y should be treated as a free area.
An AT entry is created and added to the end of the FSL_FAT area.

By optimizing the directory area,
The first sector of the directory area has a sector ID of (Y +
This is the sector indicated by 1). Therefore, the memory controller 102 assigns a sector ID: (Y + 1) indicating the head sector of the latest directory area to a new D-SI
D is added to an additional write area in the hook area as shown in FIG.

When the additional recording area in the hook area becomes full, the memory controller 102 updates the hook area of the flash memory 101. On this occasion,
As described above, in the initial format, the hook area is arranged in the sector with the sector ID: 0. Update of hook area FIG. 17 is a diagram showing a subroutine flow for performing the update of the hook area.

In FIG. 17, the memory controller 10
2 is the latest D recorded at the end of the hook area.
-Store the SID in its built-in register A (not shown) (step S1). Next, the memory controller 102
Deletes all recorded contents in the hook area (step S2). Next, the memory controller 102
Re-records the identification ID and CB at the head of the hook area, respectively, and reads them (step S3). Next, the memory controller 102 determines whether or not reading of each of the identification ID and CB has been normally performed (step S4). If it is determined in step S4 that the reading has been normally performed, the memory controller 102 stores 9 in a built-in register (not shown) as a pointer (number of bytes) n indicating the writing position (step S5). Next, the memory controller 102
Records the latest D-SID stored in the built-in register A in the n-th byte and reads it out (step S6). That is, the recorded identification ID and CB
Then, the D-SID is recorded. Next, the memory controller 102 determines whether or not the reading of the D-SID has been normally performed (Step S7).
If it is determined in step S7 that the reading has been performed normally, the memory controller 102 exits this hook area update routine and returns to the operation of the main routine (not described).

On the other hand, if it is determined in step S7 that the reading has not been performed normally, the memory controller 102 stores the value obtained by adding 4 bytes to the pointer n in the internal register as a new pointer n ( Step S8). Next, the memory controller 1
In the step 02, it is determined whether or not the pointer n is larger than the size of the hook area, that is, whether or not the total number N of bytes in one sector (step S9). When it is determined in step S9 that the pointer n is not larger than the total number of bytes N in one sector, the memory controller 102
It returns to the operation of step S6. On the other hand, if it is determined in step S9 that the pointer n is larger than the total number of bytes N in one sector, the memory controller 1
02 erases all the recorded contents of this sector (step S10). After the end of the step S10, or when it is determined in the step S4 that the reading of the identification ID and the CB has not been performed normally,
The memory controller 102 proceeds to the execution of the hook area saving routine (step S11). That is, at this time, since the sector allocated to the hook area is considered to be a bad sector, the memory controller 102 proceeds to the execution of the following hook area saving routine to save the hook area in another sector. is there.

FIG. 18 is a diagram showing the hook area retreat routine. In FIG. 18, first, the memory controller 102 searches for an empty sector based on the recorded contents of the FSL_FAT area, and selects this as a sector to be a new hook area (step S22). next,
The memory controller 102 stores 1 as a pointer n in a built-in register (not shown) (step S23).
Next, the memory controller 102 records the sector ID of the selected sector in the n-th byte of the defective sector, and reads it. Further, the memory controller 102 records data in which the sector ID of the selected sector is bit-inverted in the (n + 4) byte of the defective sector, and reads the data (step S24). Next, the memory controller 102 determines whether or not the reading in step S24 has been performed normally (step S25). If it is determined in step S25 that the reading has not been performed normally, the memory controller 102
Records data other than the bit-reversed data of the sector ID of the selected sector in the (n + 4) byte of the defective sector and reads it (step S26). Next, the memory controller 102 determines whether or not the reading in step S26 has been normally performed (step S27). If it is determined in step S27 that the reading has been normally performed, the memory controller 102 stores the value obtained by adding 8 bytes to the pointer n in the internal register as a new pointer n (step S28). Next, the memory controller 102
Determines whether the pointer n is smaller than the total number N of bytes in one sector (step S29). If it is determined in step S29 that the pointer n is smaller than the total number of bytes N in one sector, the memory controller 102 returns to the operation in step S24.
On the other hand, when it is determined in step S9 that the pointer n is larger than the total number N of bytes in one sector,
Alternatively, if it is determined in step S27 that the reading has not been performed normally, the memory controller 102 notifies the user that the saving operation of the hook area has failed.
The CPU 11 shown in FIG. 1 is notified (step S3).
0).

That is, if the identification ID in the hook area is the sector ID in which this hook area exists, and if CB is a value obtained by inverting all the bits of this sector ID, this hook area is normal and D-SID Is recorded normally. For example, the identification I of the hook area in the sector ID: 0
D is "00000000" (HEX) and CB is "FFFFFFFF" (HEX
If EX), this hook area is normal, and D-SID is recorded in the 4 bytes following CB.

If the identification ID in the hook area is different from the sector ID in which the hook area exists and CB is a value obtained by inverting all the bits of this value, the hook area is a bad sector. This indicates that the contents of the hook area have been saved to the sector of the sector ID indicated by the identification ID. For example, the ID of the hook area at sector ID: 0 is "00000010" (HEX), and the CB is "F".
If FFFFFEF "(HEX), this sector is bad, indicating that the contents of the hook area have been saved to sector ID:" 10 "(HEX).

Further, if all the bits of the identification ID and CB in the hook area are not in an inverting relation with each other, this indicates that these 8 bytes are defective and have no meaning. Therefore, the next 8 bytes are checked as the identification ID and CB, and the above-described inspection is repeated. Even if the sector of the hook area is completed, if an 8-byte area that is in an inverse relationship (not a bad one) is not detected, the evacuation of the sector has failed.

Update of FSL_FAT Area If all the FAT entries in the first sector of the FSL_FAT area indicate invalid, the memory controller 102 updates the flash memory 101 with the FSL_FAT area. For example, in the state of FIG. 13, all the FAT entries 0 to 5 in the first sector (sector ID: R) of the FSL_FAT area are in a state where they are invalid. Therefore, the memory controller 102 erases all information recorded in the sector indicated by the sector ID: R, and sets the sector as a free area. That is, the memory controller 102 creates a FAT entry in which the sector with the sector ID: R should be treated as a free area, and adds this to the end of the FSL_FAT area.

When the erase area in the last sector of the FSL_FAT area is completely lost, the memory controller 102 searches the free area of the flash memory 101 for a free sector, and finds this free sector in the FSL_FAT area.
It is added as the last sector of the T area. For example, FIG.
In the state of, the memory controller 102
By sequentially referring to the FAT entries in the L_FAT area, it is determined that the sector indicated by the sector ID: (Q + 9) is an empty sector, and this sector is referred to as FSL_FA.
It is added as the last sector of the T area. That is, n of the sector indicated by the sector ID: (R + 2) which was the last sector of the FSL_FAT area in the state before the update.
(Q + 9) is described in the SID. Further, the memory controller 102 has an FSL as shown in FIG.
As the FT-SID of the directory entry 3, (R + 2) indicating the head sector is recorded. At this time, F
The DCB of the SL directory entry 2 is rewritten to the logical value “1”.

According to the optimization operation for each of the hook area, the directory area, and the FSL_FAT area as described above, the number of erasures of the sector can be reduced while the recording area in the flash memory 101 is enabled. Can be extended. When optimizing each area, the erase unit of the recorded contents is set to one sector. However, the present invention is not limited to this, and the same effect can be obtained by using an integral multiple of the erase block as the erase unit.

Although the flash memory is used as a storage medium in this embodiment, the present invention is effective for a memory having a limited number of times of writing.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a configuration of an information processing apparatus.

FIG. 2 is a diagram showing an initial logical format of a flash memory 101.

FIG. 3 is a diagram showing an initial format of a hook area.

FIG. 4 is a diagram showing an initial format of a directory area.

FIG. 5 is a diagram showing an initial format of an FSL_FAT area.

FIG. 6 is a diagram showing an example of a state transition of the flash memory 101 according to the memory control method of the present invention.

FIG. 7 is a diagram showing an example of a state transition of the flash memory 101 according to the memory control method of the present invention.

FIG. 8 is a diagram showing an example of a state transition of the flash memory 101 according to the memory control method of the present invention.

FIG. 9 is a diagram showing an example of a state transition of the flash memory 101 according to the memory control method of the present invention.

FIG. 10 is a diagram showing an example of a state transition of the flash memory 101 according to the memory control method of the present invention.

FIG. 11 is a diagram showing an example of a state transition of the flash memory 101 according to the memory control method of the present invention.

FIG. 12 is a diagram showing an example of a state transition of the flash memory 101 according to the memory control method of the present invention.

FIG. 13 is a diagram showing an example of a state transition of the flash memory 101 according to the memory control method of the present invention.

FIG. 14 is a diagram showing an example of a storage mode of a file A.

FIG. 15 is a diagram illustrating an example of a storage form of a file F.

FIG. 16 is a diagram for explaining an operation of optimizing a directory area.

FIG. 17 is a diagram showing a subroutine flow based on a hook area update operation.

FIG. 18 is a diagram showing a subroutine flow based on an evacuation operation of a hook area.

[Description of Signs of Main Parts]

 Reference Signs List 10 storage device 101 flash memory 102 memory controller

Claims (8)

[Claims] 1. A method for dividing a recording area of a memory into a plurality of sectors each having a predetermined recording capacity and controlling the memory in units of the sector, wherein each of the sectors is a free sector. A fat entry indicating whether or not the sector is empty is recorded in the fat area of the memory, and at the time of writing a file, a fat entry indicating a free sector is sequentially searched from the head of the fat area. The file is written to the indicated sector, and the search fat entry is rewritten to a fat entry indicating that the file is not an empty sector. When deleting the file, the file to be deleted is deleted, and the file is deleted. Create a new fat entry for an empty sector. And recording it at the end of the fat area. 2. A head sector information indicating a vacant sector among fat entries recorded in the fat area and indicating a sector in which a fat entry located at the head position is recorded is recorded. 2. The memory control method according to claim 1, wherein when writing the file, a fat entry indicating an empty sector is searched from a sector position indicated by the head sector information. 3. When all fat entries recorded in the head sector of the fat area indicate that they are not empty sectors, all recorded contents of the head sector are erased and the head sector is written. 2. The method according to claim 1, wherein the free area is a free area. 4. A directory area in which file information relating to each of the files and information indicating a position of a head sector of the fat area are recorded, and information indicating a position of a head sector of the directory area are recorded in the memory. 2. The memory control method according to claim 1, wherein a hook area is recorded and formed. 5. When the sector corresponding to the hook area becomes a bad sector, a search is made for a free sector from the fat area, and information indicating the position of the free sector is recorded in the bad sector. 5. The memory control method according to claim 1, wherein said hook area is evacuated to said empty sector by recording contents recorded in a defective sector in said empty sector. 6. The apparatus according to claim 1, wherein information indicating a connection between the respective sectors is recorded in each of the areas.
6. The method for controlling a memory according to 2, 3, 4, or 5. 7. The method according to claim 1, wherein the memory is a storage medium having a limited number of times of writing. 8. The method according to claim 1, wherein the memory is a flash memory.