JP4366420B2 - MEMORY CONTROLLER, FLASH MEMORY SYSTEM HAVING MEMORY CONTROLLER, AND FLASH MEMORY CONTROL METHOD - Google Patents

Description

  The present invention relates to a memory controller, a flash memory system including the memory controller, and a flash memory control method.

  For example, as disclosed in Patent Document 1, in a memory system using a flash memory, wear leveling control is performed so that rewriting does not concentrate on a specific physical block. There are roughly two types of wear leveling control.

  The first is wear leveling control (passive wear leveling) that controls the number of rewrites of other physical blocks to be averaged, leaving the physical blocks in which data that is not rewritten is stored. (Passive-wear-leveling) control method). The other is wear leveling control (active wear leveling (Active wear leveling)) that controls the number of rewrites of all physical blocks, including physical blocks that store data that will not be rewritten. -wear-leveling) control method).

  Here, when there are few physical blocks in which data that is not rewritten is stored, the passive wear leveling control method is suitable. However, when there are many physical blocks in which data that is not rewritten is stored, the active wear leveling control method is suitable. Accordingly, Patent Document 1 discloses passive wear depending on the frequency of rewriting data stored in the memory system (that is, depending on whether there are many or few physical blocks storing data that is not rewritten). It is described that the wear leveling control is performed in any one of the leveling control method, the active wear leveling control method, or the wear leveling control method combining these.

JP 2007-133683 A

  However, it is not always easy to select an appropriate wear leveling control method according to the frequency of rewriting data stored in the memory system.

  In Patent Document 1 described above, the user selects a wear leveling control method and sets conditions. At that time, the user needs to select an appropriate wear leveling control method and set the condition. These are burdens on the user. If the wear leveling control method is not selected properly, for example, it is unnecessary if the active wear leveling control method is selected when there are few physical blocks that store data that will not be rewritten. Data transfer is often performed.

  Therefore, the present invention provides a memory controller, a flash, and the like that perform wear leveling control including a physical block only when there is a physical block in which data that is hardly rewritten (data with low rewrite frequency) is stored. An object of the present invention is to provide a memory system and a flash memory control method.

A memory controller according to a first aspect of the present invention is a memory controller that controls access to a flash memory that is erased in units of physical blocks based on an access instruction given from a host system,
Logical block allocating means for allocating a logical block composed of a plurality of sectors in the logical address space on the host system side to the physical block;
Address translation table management means for managing an address translation table indicating a correspondence relationship between the logical block and the physical block set by the logical block allocation means;
Table storage that is the physical block that is the storage destination of the address conversion table when the correspondence relationship between at least some of the logical blocks and the physical block in the address conversion table is changed by the address conversion table management unit Address conversion table storage means for storing the address conversion table in a block;
A table storage block management means for newly allocating another physical block as the table storage block when there is no more free space for storing the address conversion table in the table storage block;
When the table storage block management means assigns a new table storage block, the previous count value that is the count value that matches the count value stored in the table storage block that has no free space Count information writing means for writing the latest count value, which is the updated count value, into the physical block newly assigned as the table storage block;
Version number information determining means for determining version number information to be written in the physical block to which the logical block is newly allocated based on the latest count value;
Version number information writing means for writing the version number information determined by the version number information determining means into the physical block to which the logical block is newly assigned;
Determining means for determining whether to transfer the data stored in the physical block to another physical block based on the version number information written in the physical block;
Data transfer means for transferring data stored in the physical block that is the object of the positive determination to another physical block when a positive determination is made by the determination means;
Is provided.

A memory controller according to a second aspect of the present invention is a memory controller that controls access to a flash memory to be erased in units of physical blocks based on an access instruction given from a host system,
Logical block allocating means for allocating a logical block composed of a plurality of sectors in the logical address space on the host system side to the physical block;
Address translation table management means for managing an address translation table indicating a correspondence relationship between the logical block and the physical block set by the logical block allocation means;
Table storage that is the physical block that is the storage destination of the address conversion table when the correspondence relationship between at least some of the logical blocks and the physical block in the address conversion table is changed by the address conversion table management unit Address conversion table storage means for storing the address conversion table in a block;
A table storage block management means for newly allocating another physical block as the table storage block when there is no more free space for storing the address conversion table in the table storage block;
When the physical block allocated as the table storage block changes, the management information indicating the physical block allocated as the table storage block is the management information that is the physical block of the storage destination of the management information Management information storage means to be stored in the block;
Management information block management means for newly allocating another physical block as the management information block when there is no free space for storing the management information in the management information block;
When the management information block management means assigns a new management information block, the count value immediately before is a count value that matches the count value stored in the management information block that has no free space. Count information writing means for writing the latest count value, which is the updated count value, into the physical block newly assigned as the management information block;
Version number information determining means for determining version number information to be written in the physical block to which the logical block is newly allocated based on the latest count value;
Version number information writing means for writing the version number information determined by the version number information determining means into the physical block to which the logical block is newly assigned;
Determining means for determining whether to transfer the data stored in the physical block to another physical block based on the version number information written in the physical block;
Data transfer means for transferring data stored in the physical block that is the object of the positive determination to another physical block when a positive determination is made by the determination means;
Is provided.

A memory controller according to a third aspect of the present invention is a memory controller that controls access to a flash memory that is erased in units of physical blocks, based on an access instruction given from a host system.
Block management means for managing a correspondence relationship between a logical block composed of a plurality of sectors in the logical address space on the host system side and the physical block;
Means for searching for the physical block in the erased state in the flash memory, the free block searching means for determining in a predetermined order whether or not the physical block in the flash memory is in an erased state;
Logical block allocation means for allocating the logical block to the physical block in the erased state detected by the free block search means;
Version number information management means for updating the version number information to be written in the physical block to which the logical block is assigned each time the search in the predetermined order in the empty block search means circulates a predetermined number of times,
Version number information writing means for writing the version number information to the physical block to which the logical block is newly assigned;
Determining means for determining whether to transfer the data stored in the physical block to another physical block based on the version number information written in the physical block;
Data transfer means for transferring data stored in the physical block that is the object of the positive determination to another physical block when a positive determination is made by the determination means;
Is provided.

A memory controller according to a fourth aspect of the present invention is a memory controller that controls access to a flash memory that is erased in physical block units based on an access instruction given from a host system,
Block management means for managing a correspondence relationship between a logical block composed of a plurality of sectors in the logical address space on the host system side and the physical block;
Count means for updating the count value each time the logical block is newly assigned to the physical block, and version number information to be written to the physical block to which the logical block is assigned when the count value reaches a predetermined value Version information management means for updating
Version number information writing means for writing the version number information to the physical block to which the logical block is newly assigned;
Determining means for determining whether to transfer the data stored in the physical block to another physical block based on the version number information written in the physical block;
Data transfer means for transferring data stored in the physical block that is the object of the positive determination to another physical block when a positive determination is made by the determination means;
Is provided.

  In a preferred embodiment, the version number information is information indicating at least three types of version numbers prepared in advance that circulate in a predetermined order. The physical block that is the object of the positive determination is a physical block that stores the version number information that is more than a predetermined order before the current version number information.

A flash memory system according to the fifth aspect of the present invention provides:
A memory controller according to any one of the first to fourth aspects of the present invention;
Flash memory accessed by the memory controller;
Is provided.

A flash memory control method according to a sixth aspect of the present invention is a flash memory control method for controlling access to a flash memory to be erased in units of physical blocks based on an access instruction given from a host system,
A logical block allocation step for allocating a logical block composed of a plurality of sectors in the logical address space on the host system side to the physical block;
An address translation table management step for managing an address translation table indicating a correspondence relationship between the logical block and the physical block set by the logical block allocation step;
When the address translation table management step changes the correspondence between at least some of the logical blocks and the physical block in the address translation table, the table is the physical block that is the destination of the address translation table. An address conversion table storage step for storing the address conversion table in a block;
A table storage block management step for newly allocating another physical block as the table storage block when there is no more free space in the table storage block for storing the address conversion table;
When a new table storage block is allocated by the table storage block management step, the count value immediately before is a count value that matches the count value stored in the table storage block that has no free space. A count information writing step of writing the latest count value, which is the updated count value, into the physical block newly assigned as the table storage block;
A version number information determining step for determining version number information to be written in the physical block to which the logical block is newly allocated based on the latest count value;
A version number information writing step of writing the version number information determined in the version number information determination step into the physical block to which the logical block is newly assigned;
A determination step of determining whether or not to transfer data stored in the physical block to another physical block based on the version number information written in the physical block;
A data transfer step of transferring data stored in the physical block to be subjected to the positive determination to another physical block when a positive determination is made by the determination step;
Is provided.

A flash memory control method according to a seventh aspect of the present invention is a flash memory control method for controlling access to a flash memory that is erased in units of physical blocks based on an access instruction given from a host system,
A logical block allocation step for allocating a logical block composed of a plurality of sectors in the logical address space on the host system side to the physical block;
An address translation table management step for managing an address translation table indicating a correspondence relationship between the logical block and the physical block set by the logical block allocation step;
When the address translation table management step changes the correspondence between at least some of the logical blocks and the physical block in the address translation table, the table is the physical block that is the destination of the address translation table. An address conversion table storage step for storing the address conversion table in a block;
A table storage block management step for newly allocating another physical block as the table storage block when there is no more free space in the table storage block for storing the address conversion table;
When the physical block allocated as the table storage block changes, the management information indicating the physical block allocated as the table storage block is the management information that is the physical block of the storage destination of the management information A management information storage step to be stored in the block;
A management information block management step for newly assigning another physical block as the management information block when there is no more free space in the management information block for storing the management information;
When a new management information block is allocated by the management information block management step, a count value immediately before that is a count value that matches a count value stored in the management information block that has no free space A count information writing step of updating and writing the latest count value, which is the updated count value, to the physical block newly assigned as the management information block;
A version number information determining step for determining version number information to be written in the physical block to which the logical block is newly allocated based on the latest count value;
A version number information writing step of writing the version number information determined in the version number information determination step into the physical block to which the logical block is newly assigned;
A determination step of determining whether or not to transfer data stored in the physical block to another physical block based on the version number information written in the physical block;
A data transfer step of transferring data stored in the physical block to be subjected to the positive determination to another physical block when a positive determination is made by the determination step;
Is provided.

A flash memory control method according to an eighth aspect of the present invention is a flash memory control method for controlling access to a flash memory to be erased in units of physical blocks based on an access instruction given from a host system,
A block management step for managing the correspondence between a logical block composed of a plurality of sectors in the logical address space on the host system side and the physical block;
A search for the physical block in the erased state in the flash memory, and a free block search step for determining in a predetermined order whether or not the physical block in the flash memory is in an erased state;
A logical block allocation step of allocating the logical block to the physical block in the erased state detected in the empty block search step;
A version number information management step for updating version number information to be written in the physical block to which the logical block is allocated each time the search in the predetermined order in the empty block search step circulates a predetermined number of times,
A version number information writing step for writing the version number information to the physical block to which the logical block is newly assigned;
A determination step of determining whether or not to transfer data stored in the physical block to another physical block based on the version number information written in the physical block;
A data transfer step of transferring data stored in the physical block to be subjected to the positive determination to another physical block when a positive determination is made by the determination step;
Is provided.

A flash memory control method according to a ninth aspect of the present invention is a flash memory control method for controlling access to a flash memory to be erased in units of physical blocks based on an access instruction given from a host system,
A block management step for managing the correspondence between a logical block composed of a plurality of sectors in the logical address space on the host system side and the physical block;
A count step of updating a count value each time the logical block is newly assigned to the physical block, and version number information to be written to the physical block to which the logical block is assigned when the count value reaches a predetermined value Version number information management step to update,
A version number information writing step for writing the version number information to the physical block to which the logical block is newly assigned;
A determination step of determining whether or not to transfer data stored in the physical block to another physical block based on the version number information written in the physical block;
A data transfer step of transferring data stored in the physical block to be subjected to the positive determination to another physical block when a positive determination is made by the determination step;
Is provided.

  Memory controller, flash memory system, and flash memory in which wear leveling control including physical blocks is performed only when there is a physical block that stores data that is hardly rewritten (data that is rewritten less frequently) A control method can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram schematically showing a flash memory system 1 according to an embodiment of the present invention.

  As shown in FIG. 1, the flash memory system 1 includes a flash memory 2 and a memory controller 3 that controls the flash memory 2.

  The flash memory system 1 is connected to the host system 4 via the external bus 13. The host system 4 is composed of a CPU (Central Processing Unit) for controlling the entire operation of the host system 4, a companion chip for transferring information to and from the flash memory system 1, and the like. The host system 4 may be various information processing apparatuses such as a personal computer and a digital still camera that process various types of information such as characters, sounds, and image information.

  As shown in FIG. 1, the memory controller 3 includes a microprocessor 6, a host interface block 7, a work area 8, a buffer 9, a flash memory interface block 10, an ECC (Error Collection Code) block 11, and a ROM. (Read Only Memory) 12. The memory controller 3 is connected to the flash memory 2 via the internal bus 14. The memory controller 3 constituted by these functional blocks is integrated on one semiconductor chip. Hereinafter, each functional block will be described.

  The host interface block 7 exchanges data, address information, status information, external commands and the like with the host system 4. The external command is a command for the host system 4 to instruct the flash memory system 1 to execute processing. Data or the like supplied from the host system 4 to the flash memory system 1 is taken into the flash memory system 1 (for example, the buffer 9) using the host interface block 7 as an entrance. Data supplied from the flash memory system 1 to the host system 4 is supplied to the host system 4 through the host interface block 7 as an exit.

  The host interface block 7 includes a command register R1, a sector number register R2, and an LBA register R3. Information given from the host system 4 is written in the command register R1, the sector number register R2, and the LBA register R3. External commands such as a write command and a read command are written in the command register R1. The number of sectors in the access target area is written in the sector number register R2. LBA (Logical Block Address) (described later) of the access target area is written in the LBA register R3.

  The work area 8 is a work area for temporarily storing data necessary for controlling the flash memory 2, and is composed of a plurality of SRAM (Static Random Access Memory) cells. The work area 8 stores, for example, an address conversion table (described later) indicating the correspondence between logical blocks and physical blocks.

  The buffer 9 holds the data read from the flash memory 2 until the host system 4 can receive the data. The buffer 9 holds data to be written to the flash memory 2 until the flash memory 2 is in a writable state.

  The flash memory interface block 10 exchanges data, address information, status information, internal commands, and the like with the flash memory 2 via the internal bus 14. Here, the internal command is a command for the memory controller 3 to instruct the flash memory 2 to execute processing, and the flash memory 2 operates according to the internal command given from the memory controller 3.

  The ECC block 11 generates an error correction code (ECC) added to data to be written to the flash memory 2 and is included in the read data based on the error correction code added to the read data. Detect and correct errors.

  The ROM 12 is a non-volatile storage element that stores a program that defines a processing procedure performed by the microprocessor 6. For example, a program that defines a processing procedure such as creation of an address conversion table is stored.

  The microprocessor 6 controls the overall operation of the memory controller 3 in accordance with a program stored in the ROM 12. For example, the microprocessor 6 causes the flash memory interface block 10 to execute processes based on a command set that defines various processes read from the ROM 12.

  The flash memory 2 is a NAND flash memory. The NAND flash memory includes a register and a memory cell array in which a plurality of memory cells are two-dimensionally arranged. The memory cell array includes a plurality of memory cell groups and word lines. Here, the memory cell group is a group in which a plurality of memory cells are connected in series. Each word line is for selecting a specific memory cell in the memory cell group. Data is written from the register to the selected memory cell or data is read from the selected memory cell to the register between the selected memory cell and the register via the word line.

  In the NAND flash memory, a data read operation and a data write operation are performed in units of pages, and a data erase operation is performed in units of blocks (physical blocks). A physical block is composed of a plurality of pages (physical pages). For example, one physical page includes a user area of a predetermined size (for example, 2048 bytes) and a redundant area of a predetermined size (for example, 64 bytes), and one physical block has a predetermined number (for example, 64). It consists of physical pages. The user area is an area for storing data given from the host system 4, and is configured by a predetermined number (for example, four) of physical sector areas (storage areas in units of 512 bytes). The redundant area is an area for storing additional data such as an error correction code (ECC), logical address information, block status (flag), and count information (described later).

  The logical address information is information for determining the correspondence between physical blocks and logical blocks. Therefore, for a physical block having no corresponding logical block, such as a physical block from which stored data has been erased, no logical address information is stored in the redundant area of the physical block. In the following description, the “redundant area of the physical block” refers to a storage area configured by a redundant area (for example, a redundant area of the first physical page) included in one or more physical pages in the physical block.

  The block status (flag) is a flag indicating pass / fail of the physical block. For the initial defective physical block, a block status (flag) indicating a defective block (physical block in which data cannot be normally written) is written by the manufacturer. Some manufacturers also write a block status (flag) indicating the initial defective physical block in the user area.

  In the writing process of the present embodiment, the host system 4 writes a command code indicating a write command in the command register R1, writes the number of sectors of data to be written in the sector number register R2, and stores in the LBA register R3 The LBA corresponding to the top data to start writing is written. Based on the information written in the sector number register R2 and the LBA register R3, a logical access area that is an access target area is determined and given to the physical block corresponding to the logical block including the logical access area from the host system 4. Data is written.

  When the logical access area determined based on the information written in the sector number register R2 and the LBA register R3 extends over a plurality of logical blocks, there are a plurality of physical blocks to which data is written. Therefore, when the logical access area extends over a plurality of logical blocks, the area is divided for each logical block to which the logical access area belongs, and data write processing is performed. For example, when the logical access area extends over two logical blocks (the first logical block and the second logical block), the write processing for the physical block corresponding to the first logical block and the second logical block Write processing is performed on the physical block corresponding to the block. Data instructed to be written to the logical access area belonging to the first logical block is written to the physical corresponding to the first logical block. Data instructed to be written to the logical access area belonging to the second logical block is written into the physical block corresponding to the second logical block.

  The address space on the host system 4 side is managed by an LBA (Logical Block Address) which is a serial number assigned to an area (hereinafter referred to as a logical sector area) divided in units of sectors (512 bytes). Also, a logical block composed of a plurality of logical sector areas is formed, and one or a plurality of physical blocks are assigned to the logical block.

  The correspondence between logical blocks and physical blocks is often managed on a zone basis. Specifically, one logical zone is composed of a plurality of logical blocks, one physical zone is composed of a plurality of physical blocks, and the logical zone is managed in association with the physical zone. Many.

  However, in this case, when access is concentrated in a specific logical zone, the number of rewrites of physical blocks included in the physical zone corresponding to the logical zone where access is concentrated is greater than the number of rewrites of physical blocks included in other physical zones. Is also undesirable.

  As a method for solving this problem, there is a method in which logical blocks having consecutive logical block numbers (LBNs), which are serial numbers assigned to the logical blocks, are allocated to each logical zone.

  However, when access concentrates on a specific logical block (when the access concentration range does not extend over a plurality of logical blocks), the physical included in the physical zone corresponding to the logical zone including the logical block The number of block rewrites is larger than the number of rewrites of physical blocks included in other physical zones. In such a case, it is preferable not to limit the physical blocks that can be associated with the logical blocks included in each logical zone. In other words, it is preferable that a logical block included in each logical zone can correspond to any physical block without forming a physical zone.

  The correspondence between logical blocks and physical blocks is usually managed by an address conversion table that is a table describing the correspondence between logical blocks and physical blocks. When the correspondence between the logical block and the physical block changes, the address conversion table is updated in the work area (SRAM) 8. The address conversion table is generally created based on logical address information stored in the redundant area of each physical block at the time of startup or access, but is stored in the flash memory 2 and read from the flash memory 2. You can also. As a result, the address conversion table can be obtained in a shorter time than reading the logical address information from the redundant area of each physical block and creating the address conversion table. In particular, the address translation table is stored in the flash memory 2 when the logical blocks included in each logical zone can be associated with any physical block without configuring the physical zone as described above. It is better to keep it.

  When the address conversion table is stored in the flash memory 2, it is preferable that the latest address conversion table is always stored in the flash memory 2 in order to cope with a sudden power interruption. That is, each time the correspondence between the logical block and the physical block changes (that is, every time the address conversion table is updated on the work area 8), the latest address conversion table is stored in the flash memory 2. Is preferred. Considering the time taken to store the address conversion table in the flash memory 2, it is preferable to store (manage) the address conversion table in units of logical zones and reduce the number of logical blocks included in each logical zone. .

  Therefore, in this embodiment, as shown in FIG. 2, a logical zone is formed, but a physical zone is not formed. Regardless of which logical zone, the entire range of physical blocks is assigned to each logical zone. Accordingly, any logical block may be assigned to any physical block.

  In the present embodiment, an address conversion table is prepared for each logical zone as shown in FIG. Each address conversion table manages which logical block corresponds to which physical block only for each logical block constituting the corresponding logical zone. In FIG. 3, reference numeral 103-0 is an address conversion table corresponding to a logical zone whose logical zone number (LZN), which is a serial number assigned to the logical zone, is # 0. It is an address conversion table corresponding to the logical zone # 1. Each address conversion table (103-0 and 103-1) includes the LBN of the logical block and the physical block address of the physical block to which the logical block is assigned (for each logical block constituting the corresponding logical zone). PBA) is recorded. For this reason, the size of each address conversion table (address conversion table for each logical zone) is smaller than when all logical blocks are managed by one address conversion table. The address conversion table for each logical zone is stored in different physical blocks. In other words, two or more address translation tables corresponding to two or more logical zones are not simultaneously stored in the same physical lock. For example, the address conversion table 103-0 corresponding to the logical zone of LZN # 0 is stored in the physical block of PBA # 5, and the address conversion table 103-1 corresponding to the logical zone of LZN # 1 is stored in PBA # 1076. Stored in physical block. Hereinafter, the physical block where the address translation table is stored is referred to as a “table storage block”. Each time the address conversion table is updated on the work area 8, as shown in FIG. 3, an area in the physical block that is the table storage block (one or more free physical pages or free areas in the physical page) is stored. Saved. For example, if the address conversion table for each logical zone is set to a size that can be stored in one physical page, and the address conversion table is stored in order from the first physical page every time the address conversion table is updated, The table storage block can store 64 address conversion tables. When 64 address conversion tables are stored in this table storage block and there is no free area in which the address conversion table can be stored, another physical block is allocated as a table storage block. As shown in FIG. 3, the address conversion table 103-1 is stored up to the last physical page # 63 of the physical block of PBA # 1076 which is the table storage block of the address conversion table corresponding to the logical zone of LZN # 1. If there is, there is no empty area for storing the address translation table in the physical block of PBA # 1076. Therefore, if the address translation table 103-1 is updated thereafter, another physical block (empty physical block) is assigned as the table storage block of the address translation table 103-1, and the other physical block is assigned to the other physical block. The updated address conversion table 103-1 is stored. Hereinafter, such a process in which another physical block is allocated as a table storage block is referred to as “a table storage block change”.

  In this embodiment, the memory controller 3 manages information (hereinafter referred to as “table management information”) indicating in which physical block the address translation table corresponding to which logical zone is stored. In the example shown in FIG. 3, the table management information 101 includes information that can determine the correspondence between the LZN of each logical zone and the PBA of the table storage block of the address conversion table corresponding to the logical zone of the LZN. Yes. By referring to this table management information 101, for example, the table storage block of the address translation table 103-0 corresponding to the logical zone of LZN # 0 is a physical block of PBA # 5, or the logical block of LZN # 1 It can be seen that the table storage block of the address conversion table 103-1 corresponding to the zone is a physical block of PBA # 1076. The table management information 101 is stored in any one of two or more preset physical blocks for table management information (hereinafter referred to as “management information block candidates”). In this example, PBA # 0 and PBA # 1 physical blocks (that is, two physical blocks) are set as management information block candidates. Therefore, the table management information is stored in either the physical block of PBA # 0 or PBA # 1. Hereinafter, the physical block of the storage destination of the table management information selected from the management information block candidates (physical blocks of PBA # 0 and PBA # 1) is referred to as “management information block”. The table management information 101 is updated on the work area 8 when the table storage block of the address conversion table corresponding to any logical zone is changed. Each time the table management information 101 is updated on the work area 8, a free area (one or more free physical pages or physical pages in a physical block which is a management information block (for example, a physical block of PBA # 0)) is stored. Saved in free space). If there is no free area that can store the table management information in the physical block, another physical block (for example, a physical block of PBA # 1) of the two management information block candidates is used as the management information block. Assigned. That is, two predetermined physical blocks are alternately used as management information blocks. Hereinafter, this process is referred to as “management information block switching”.

  With reference to FIG. 2, the correspondence between the logical block and the physical block will be described.

  In the present embodiment, as shown in FIG. 2, 2048000 logical sector areas composed of LBA # 0 to # 20479999 are allocated to a storage area on the flash memory 2 side composed of 8192 physical blocks.

  In FIG. 2, a group of 256 logical sector areas having consecutive addresses (LBA) is defined as a logical block, and the LBN described above is attached to this logical block. For example, the 256 logical sector areas of LBA # 0- # 255 belong to the logical block of LBN # 0, and the 256 logical sector areas of LBA # 256- # 511 belong to the logical block of LBN # 1. Yes. As described above, the 2048,000 logical sector areas of LBA # 0 to # 20479999 belong to one of 8000 logical blocks of LBN # 0 to # 7999.

  Further, a plurality of logical blocks are combined into a logical zone, and the above-described LZN is added to the logical zone. In FIG. 2, each logical block is sequentially allocated to eight logical zones LZN # 0 to # 7 so that logical blocks having consecutive LBNs belong to different logical zones. For example, the logical block of LBN # 0 is in the logical zone of LZN # 0, the logical block of LBN # 1 is in the logical zone of LZN # 1, the logical block of LBN # 2 is in the logical zone of LZN # 2, and so on. Sort to logical zone # 7. Similarly, the LBN # 8 logical block is assigned to the LZN # 0 logical zone, the LBN # 9 logical block is assigned to the LZN # 1 logical zone, and the LBN # 10 logical block is assigned to the LZN # 2 logical zone. To go. By allocating in this way, it is possible to reduce the probability that logical blocks corresponding to logical access areas with a high rewrite frequency are concentrated in a specific logical zone. Therefore, it is possible to suppress the change frequency of the table storage block corresponding to a specific logical zone from becoming significantly higher than the change frequency of the table storage block corresponding to another logical zone.

  The flash memory 2 is composed of 8192 physical blocks. A unique physical block address (PBA) is assigned to 8192 physical blocks. The flash memory 2 may have a congenital defective physical block that is defective from the time of shipment. Further, the flash memory 2 may include a physical block (acquired defective block) that deteriorates after the start of use even if it is a good physical block at the time of shipment.

  In the NAND flash memory, a data read operation and a data write operation are performed in units of pages, and a data erase operation is performed in units of physical blocks. In the data erasure operation, the data stored in the physical block corresponding to the logical block to which the logical access area belongs (hereinafter referred to as “write destination logical block”) or the latest data corresponding to the data is written in another physical block. This is performed when all the data stored in the physical block is replaced with data written in another physical block. That is, when the data stored in the physical block corresponding to the write destination logical block is all replaced with the data written in another physical block, the data stored in the physical block is erased, The correspondence relationship between the logical block and the physical block described in the address conversion table (the table describing the correspondence relationship between the logical block and the physical block) is updated. When searching for a free physical block to which a write destination logical block is newly assigned (a physical block to which no logical block is assigned) is searched, for example, a free space is sequentially provided from the first physical block to the last physical block in the flash memory 2. The physical block is searched. Then, a write destination logical block is allocated to the detected free physical block.

  As described above, when data stored in a physical block is rewritten, a logical block corresponding to the physical block is newly added to a physical block (empty physical block) different from the physical block. Will be assigned. Further, even when there is no physical block corresponding to the write destination logical block, a logical block is newly allocated to an empty physical block.

  In this embodiment, when a logical block is newly assigned to a physical block, a rewrite mark is written in the redundant area of the physical block in addition to the logical address information indicating the newly assigned logical block. It is. The “rewrite mark” referred to in the present embodiment is version number information that is updated when a result of processing related to a logical block being newly assigned to a physical block matches a predetermined condition. With respect to “processing related to the logical block being newly assigned to the physical block” and “predetermined condition”, some examples will be described in detail later.

  The rewrite marks are at least three types of information that circulate in a predetermined order. That is, the rewrite mark is updated (transitioned) in a predetermined order, and after the last rewrite mark is reached, it is updated (returned) to the first rewrite mark. For example, as shown in FIG. 4A, every time a predetermined condition is met, the memory controller 3 changes the rewrite mark to the first rewrite mark “55”, the second rewrite mark “5A”, the third rewrite mark, The rewrite mark “A5” and the fourth rewrite mark “AA” are updated in this order, and the next rewrite mark “AA” is updated to the first rewrite mark.

  Hereinafter, the process performed in the present embodiment will be described with reference to FIGS. 4B and 5, taking as an example that the rewrite mark is updated according to the rule described with reference to FIG. 4A. At this time, a period in which the rewrite mark is the first rewrite mark “55” is referred to as “first period”, and a period in which the rewrite mark is the second rewrite mark “5A” The second period ”, the period when the rewrite mark was the third rewrite mark“ A5 ”is referred to as the“ third period ”, and the rewrite mark is the fourth rewrite mark“ AA ”. This period is called “fourth period”. Since the rewrite mark circulates, the period also circulates.

  The physical block in which the first rewrite mark “55” is written is a physical block to which a logical block is newly allocated in the first period, and the second rewrite mark “5A” is written therein. The physical block is a physical block to which a logical block is newly assigned in the second period, and a physical block in which the third rewrite mark “A5” is written is newly added in the third period. The physical block to which the fourth rewrite mark “AA” is written is a physical block to which a logical block is newly allocated in the fourth period.

  Specifically, for example, in FIG. 4B, when a logical block of LBN # 41 is newly assigned to a physical block of PBA # 12 detected as an empty physical block, as shown in (4A), Since the time is within the first period, the LBN “# 41” of the newly allocated logical block and the first rewrite mark “55h” are stored in the redundant area 105 of the physical block of the PBA # 12. Written.

  Next, as shown in (4B), when a logical block of LBN # 42 is newly allocated to a physical block of PBA # 18 detected as an empty physical block, at that time also within the first period Therefore, the LBN “# 42” of the newly allocated logical block and the first rewrite mark “55h” are written in the redundant area 105 of the physical block of PBA # 18.

  After that, as shown in (4C) and (4D), a new logical block is allocated to the physical block. However, since both are within the first period, the physical block to which the new logical block is allocated In the redundant area 105, the LBN of the newly allocated logical block and the first rewrite mark “55h” are written.

  Here, in the case of (4D), that is, when a logical block of LBA # 44 is newly allocated to the PBA # 27 physical block, it is assumed that the result of processing related to the allocation matches a predetermined condition. In this case, the rewrite mark is updated from the first rewrite mark “55” to the second rewrite mark “5A”. At this point, the first period ends and the second period starts.

  Therefore, after that, for example, as shown in (4E), when a logical block of LBN # 45 is newly allocated to a physical block of PBA # 31 detected as an empty physical block, at that time, in the second period Therefore, the LBN “# 45” of the newly allocated logical block and the second rewrite mark “5Ah” are written in the redundant area 105 of the physical block of PBA # 31.

  As described above, the rewrite mark written in the redundant area of the physical block differs depending on in which period the logical block is newly allocated to the physical block.

  The free block search for searching for a physical block to which a new logical block is newly assigned is performed for all physical blocks used as a storage area of the host system 4. At that time, empty blocks are sequentially searched from the first physical block toward the last physical block for all the physical blocks. In this way, for the physical blocks included in the range to be searched, the search for empty blocks in the order from the first physical block to the last physical block is repeatedly performed, so that data that is hardly rewritten (rewrite frequency is If there is no physical block in which (low data) is stored, the number of rewrites of the physical block included in the search target range is expected to be substantially equal.

  Now, the memory controller 3 has not been rewritten at a predetermined timing (for example, when the rewrite mark is updated) for at least one period (writing after the stored data is once erased). A physical block, in other words, a physical block that has passed a period longer than at least one period from the allocation of the currently allocated logical block is searched.

  For example, a physical block that has not been rewritten for longer than one period is searched. In this case, a physical block in which a rewrite mark corresponding to a period two or more periods before the current period is stored is searched. As shown in FIG. 5, if the current rewrite mark is the second rewrite mark “5Ah”, the current period is the second period. Therefore, the physical block in which the fourth rewrite mark “AAh” or the third rewrite mark “A5” is stored is written in the first period, which is one period before the second period. It is a physical block that has not been replaced. Therefore, if the current rewrite mark is the second rewrite mark “5Ah”, the fourth rewrite mark “AAh” or the third rewrite mark that is in the order before the first rewrite mark “55”. The physical block in which the rewrite mark “A5” is stored is searched. In other words, in the example of FIG. 5, physical blocks PBA # 6, # 15, and # 16 are detected as physical blocks that have not been rewritten for longer than one period.

  In the present embodiment, a physical block that has not been rewritten for a period longer than one period is regarded as a physical block in which data with a low rewrite frequency is stored. When such a physical block is detected, the memory controller 3 performs a free block search to detect another physical block (empty block), and a physical block that is considered to store data with a low rewrite frequency. Is transferred (copied) to another physical block. Furthermore, the memory controller 3 writes the current rewrite mark in the other physical block. Specifically, for example, as shown in (5A), (5B), and (5C) of FIG. 5, the data stored in the detected physical blocks of PBA # 6, # 15, and # 16 is empty. Transferred (copied) to the physical blocks PBA # 32, # 33 and # 34 detected by the block search. In addition, LBN # 6, # 15, and # 16 are written as logical address information in the redundant area 105, and the second rewrite mark “5Ah” that is the current rewrite mark is written as PBA # 32 as the rewrite mark. , # 33 and # 34 are written.

  After this transfer process is completed, the data stored in the transfer source physical block is erased. Specifically, an internal command instructing to erase data stored in the physical blocks of PBA # 6, # 15, and # 16 is sequentially given from the memory controller 3 to the flash memory 2, and the internal command In response, the flash memory 2 erases the data stored in the physical blocks of PBA # 6, # 15 and # 16.

  It should be noted that the criteria for considering data with low rewrite frequency as stored physical blocks, that is, for how long a physical block that has not been rewritten for longer than that is considered as a physical block with low rewrite frequency stored, It can be set as appropriate in consideration of the number of periods (and / or the length of one period) until the rewrite mark is completed.

  In addition, when the number of periods until the rewrite mark is completed is small, when the rewrite mark is updated, the physical block in which the same rewrite mark as the changed rewrite mark is written in the period before the rewrite mark Care must be taken that there is no remaining. Specifically, the memory controller 3 searches for a physical block that has not been rewritten for longer than one period, and transfers (copies) data stored in the detected physical block to another physical block. It is necessary to complete the processing by the next time the rewrite mark is updated. In order to ensure this management, the memory controller 3 stores the data stored in the physical block in which data with low rewrite frequency is stored until there is no physical block that has not been rewritten for longer than one period. The transfer process may be prioritized so that commands from the host system 4 are not accepted.

  The current rewrite mark is stored in, for example, a storage area in the memory controller 3, for example, a work area 8 (a volatile memory such as SRAM). The rewrite mark stored in the work area 8 is copied (written) to the flash memory 2 at an appropriate time. When the power is turned off, the rewrite mark stored in the work area 8 is erased, but when the power is turned on, the rewrite mark stored in the flash memory 2 is read into the work area 8. Thereafter, the rewrite mark is used as the current rewrite mark. The memory controller 3 may be provided with a storage area composed of a nonvolatile RAM such as a FeRAM (Ferroelectric Random Access Memory) or MRAM (Magnetic Random Access Memory), and a rewrite mark may be held in this storage area. When the rewrite mark is held in such a nonvolatile RAM, the rewrite mark can be managed on the nonvolatile RAM, and it is not necessary to copy the rewrite mark to the flash memory 2.

  In addition, a physical block regarded as a physical block in which data with low rewrite frequency is stored is erased after the data stored in the physical block is transferred (copied) to another physical block, It is considered as an empty physical block. There is a possibility that the physical block that has been made empty has a small number of rewrites up to that point. However, since it becomes an empty block, the possibility that the number of rewrites thereafter will increase is high. Conversely, the physical block that is the data copy destination may have a large number of rewrites up to that point, but the data with a low rewrite frequency may be copied, which may reduce the number of subsequent rewrites. Get higher. Based on such a principle, it can be expected that the number of rewrites of a plurality of physical blocks in the flash memory 2 is equalized.

  The outline of the flow of processing performed in the present embodiment will be described below with reference to FIG.

  First, initial setting is performed (step 101). For example, the memory controller 3 sets the current rewrite mark.

  When a write command is received from the host system 4 after the initial setting, the memory controller 3 needs to newly set a physical block corresponding to the logical block to which the logical access area specified by the write command belongs. Is determined (step 102). If it is necessary (YES in step 102), a free block search is performed, and a logical block to which the logical access area designated by the write command belongs is allocated to the detected free block (step 103). Specifically, the LBN of the logical block to which the logical access area designated by the write command and the current rewrite mark are written in the redundant area 105 of the detected empty block (physical block). The processing related to newly assigning a logical block to a physical block is also executed in this step 103. If the result of the process matches a predetermined condition, the rewrite mark is updated, and if the result does not match the predetermined condition, the rewrite mark is not changed.

  The memory controller 3 determines whether or not the rewrite mark has been updated in step 103 (step 104), and if it has been updated (YES in step 104), search processing of the physical block in which data with low rewrite frequency is stored I do. When a physical block storing data with low rewrite frequency is detected, the memory controller 3 performs a data transfer process for copying the data stored in the detected physical block to another physical block ( Step 105). Specifically, a physical block that has not been rewritten for a period longer than one period is searched, and when such a physical block is detected, the data stored in the detected physical block is another physical block. Forwarded to After this transfer is completed, the data stored in the detected physical block is erased.

  According to the above description, when a logical block is newly assigned to a physical block, a rewrite mark is written to the physical block. The rewrite mark is version number information that is updated when a result of processing related to a logical block newly assigned to a physical block matches a predetermined condition. A physical block in which a rewrite mark two or more orders before the rewritten mark after the update is stored is regarded as a physical block in which data with a low rewrite frequency is stored. The wear leveling control including the physical block is performed only when there is a physical block storing such data with low rewrite frequency.

  As described above, the rewrite mark is version number information that is updated when a result of processing related to a new allocation of a logical block to a physical block matches a predetermined condition. Any of the following first to fourth examples can be adopted as a process related to a new allocation of a logical block to a physical block and a predetermined condition. Hereinafter, each example will be described in detail.

  <First example>.

  In the first example, “a process related to a logical block being newly assigned to a physical block” means a count value (hereinafter, referred to as the number of changes of the physical block (table storage block) of the storage destination of the address translation table). (Referred to as “change count value”) is counted up (or counted down), and “predetermined condition” is that the change count value becomes a predetermined value.

  The change count value is counted up (or counted down) every time the table storage block is changed. The changed count value after counting up (or after counting down) is written to the table storage block. Thereby, it is possible to grasp how many times the table storage block has been changed from the change count value stored in the table storage block. As described above, since the change count value is written in the table storage block instead of the rewrite mark, the data provided from the host system is stored in the flash memory 2 as shown in FIG. 7A. Existing physical blocks (hereinafter referred to as “data storage blocks”) and table storage blocks (physical blocks of PBA # 5 and PBA # 14) in which the address translation table is stored are mixed. If the rewrite mark and the change count value are set so as not to overlap, the physical block is a data storage block depending on whether the rewrite mark is written or the change count value is written. Or a table storage block. For the data storage block, information indicating that the data storage block is stored (information indicating which logical zone's address conversion table is stored) may be written instead of the logical address information.

  In this first example, it is determined in advance how many times the table storage block is changed to update the rewrite mark. That is, a predetermined value for the change count value is set in advance. When the table storage block is changed, the change count value is counted up (or counted down). When the changed count value after the count up (or count down) reaches a predetermined value, the rewrite mark is updated. The For example, when the predetermined value is 15 (0Fh), the rewrite mark is updated when 15 (0Fh) is written as the change count value in the newly allocated table storage block. In the case of the present embodiment, if the change count value is returned to 15 (0Fh) and then 0 (00h), the rewrite mark and the change count value will not overlap.

  Note that it is possible to appropriately set which logical zone's address conversion table is to be updated based on the change count value of the table storage block in which the address conversion table is stored. Further, the current rewrite mark may be stored in the table storage block.

  Hereinafter, the flow of processing relating to the first example will be described.

  For example, the memory controller 3 executes the process shown in FIG. 7B in S103 of FIG. In other words, when the address change table is updated by newly assigning a logical block to a physical block, the memory controller 3 can store the updated address conversion table in the physical block that is a table storage block. It is determined whether or not a physical page remains (S111).

  If it is a determination result that it does not remain (S111: YES), the memory controller 3 executes S112. That is, the memory controller 3 searches for another physical block (empty block) by searching for a free block, and uses the detected other physical block as a new table storage block (that is, changes the table storage block). Further, the memory controller 3 reads the change count value stored in the physical block that was the table storage block before the change from the physical block, and counts up (or counts down) the change count value. Then, the memory controller 3 writes the changed count value after the count-up (or after the count-down) and the updated address conversion table in the other physical block (empty block) that is the table storage block after the change. Further, the memory controller 3 updates the PBA corresponding to the LZN of the logical zone corresponding to the address conversion table in the table management information 101 (see FIG. 3) to the PBA of the changed table storage block.

  Thereafter, the memory controller 3 determines whether or not the changed count value after counting up (or counting down) is a predetermined value (S113). If the change count value is a predetermined value (S113: YES), the memory controller 3 updates the rewrite mark (S114).

  The above is the description of the first example. The current rewrite mark is preferably stored in the flash memory 2 or the nonvolatile RAM.

  <Second example>.

  In the second example, “processing related to a logical block being newly assigned to a physical block” is a count value (hereinafter, referred to as the number of times of switching of a physical block (management information block) as a storage destination of table management information. (Referred to as “switch count value”) is counted up (or counted down), and “predetermined condition” is that the switch count value becomes a predetermined value.

  The switching count value is counted up (or counted down) every time the management information block is changed. The switching count value is written in the management information block. Thereby, it is possible to grasp how many times the management information block is switched from the switching count value stored in the management information block.

  The management information block is selected from management information block candidates. In the example shown in FIG. 8A, physical blocks PBA # 0 and PBA # 1 are management information block candidates. Therefore, the physical block of PBA # 0 or PBA # 1 is used as the management information block. The current rewrite mark may be written in this management information block.

  In this example, the physical block of PBA # 0 or PBA # 1 is not assigned to the table storage block or the data storage block. Further, it is not necessary to write the change count value in the table storage block.

  In this second example, it is determined in advance how many times the management information block is switched to update the rewrite mark. That is, a predetermined value for the switching count value is set in advance. When the management information block is switched, the switching count value is counted up (or counted down). When the switching count value after counting up (or counting down) reaches a predetermined value, the rewrite mark is updated. The The predetermined value may be one or plural (for example, a multiple of a certain natural number).

  Hereinafter, the flow of processing relating to the second example will be described.

  For example, the memory controller 3 executes the process shown in FIG. 8B in S103 of FIG. That is, when the memory controller 3 updates the table management information in accordance with the change of the table storage block, a free physical page that can store the updated table management information remains in the physical block that is the management information block. It is determined whether or not (S121).

  If it is a determination result that it does not remain (S121: YES), the memory controller 3 executes S122. That is, the memory controller 3 sets the other physical block of the two management information block candidates described above as a new management information block (that is, switches the management information block). Further, the memory controller 3 reads the switching count value stored in the physical block that was the management information block before switching from the physical block, and counts up (or counts down) the switching count value. Then, the memory controller 3 writes the switching count value after counting up (or after counting down) and the updated table management information in the other physical block that is the management information block after switching.

  Thereafter, the memory controller 3 determines whether or not the switching count value after counting up (or counting down) is a predetermined value (S123). If the switching count value is a predetermined value (S123: YES), the memory controller 3 updates the rewrite mark (S124).

  The above is the description of the second example. The current rewrite mark is preferably stored in the flash memory 2 or the nonvolatile RAM.

  <Third example>.

  In the third example, “a process related to a logical block being newly assigned to a physical block” is a search for a free block performed in the order from the first physical block to the last physical block. The “condition” is that the search for empty blocks has been completed. A free block search is a complete search for a free block that starts from the first physical block and goes back to the last physical block.

  For example, the memory controller 3 executes the process shown in FIG. 9A in S103 of FIG. That is, the memory controller 3 updates the rewrite mark (S132) when the search for the empty block is completed (S131: YES).

  The current rewrite mark is preferably stored in the flash memory 2 or the nonvolatile RAM. Further, it is preferable that the search start block (physical block for starting the next search) in the search for the empty block is also stored in the flash memory 2 or the nonvolatile RAM. In the third example, the predetermined condition is that the search for the empty block has been completed. However, the predetermined condition is that the circulation is not limited to a single cycle, and the predetermined number of cycles may be two or more. . In this case, on the work memory (SRAM) 8, the count value indicating the number of cycles for searching for an empty block is updated every time an empty block search is completed. It is preferable that the number of circulations is also stored in the flash memory 2 or the nonvolatile RAM.

  <Fourth example>.

  In the fourth example, “processing related to a logical block being newly assigned to a physical block” means a count value indicating the number of times a logical block is newly assigned to a physical block (hereinafter referred to as “allocation count value”). ”) Is counted up (or counted down), and the“ predetermined condition ”is that the assigned count value becomes a predetermined value.

  The allocation count value is counted up (or counted down) every time a logical block is newly allocated to a physical block. Therefore, it is possible to grasp how many times a logical block is newly allocated to the physical block from the allocation count value.

  In the fourth example, it is determined in advance how many times a logical block is newly assigned to a physical block when the rewrite mark is updated. That is, a predetermined value for the allocation count value is set in advance. The predetermined value may be one or plural (for example, a multiple of a certain natural number).

  For example, the memory controller 3 executes the process shown in FIG. 9B in S103 of FIG. That is, when a logical block is newly allocated to a physical block, the memory controller 3 counts up (or counts down) the allocation count value, for example, on the work memory (SRAM) 8 (S141). Then, the memory controller 3 determines whether or not the assigned count value after counting up (or counting down) has reached a predetermined value (S142). If the allocation count value is a predetermined value (S142: YES), the memory controller 3 updates the rewrite mark (S143).

  The above is the description of the fourth example. The current rewrite mark and the assigned count value are preferably stored in the flash memory 2 or the nonvolatile RAM. Further, the allocation count value may be written in a physical block to which a new logical block is allocated.

  As mentioned above, embodiment of this invention mentioned above is an illustration for description of this invention, and is not the meaning which limits the scope of the present invention only to those embodiment. Those skilled in the art can implement the present invention in various other modes without departing from the gist of the present invention. For example, the memory controller 3 may select one of the first to fourth examples and update the rewrite mark based on the selected example. Specifically, for example, the memory controller 3 has a first mode in which the rewrite mark is updated under conditions based on the first example, and a second mode in which the rewrite mark is updated under conditions based on the second example. And a third mode in which the rewrite mark is updated under the condition based on the third example, and a fourth mode in which the rewrite mark is updated under the condition based on the fourth example. May be selected from the first to fourth modes in accordance with an instruction from or a result of an event that has occurred, and the rewrite mark may be updated in accordance with the selected mode.

1 is a block diagram showing a schematic configuration of a flash memory system according to an embodiment of the present invention. It is a figure which shows the correspondence of a logical block and a physical block. Table management information and address conversion tables and how to store them are shown. FIG. 4A shows a rewrite mark change rule. FIG. 4B is an explanatory diagram of processing performed when a logical block is newly assigned to a physical block. It is explanatory drawing of the data transfer process performed when the physical block in which the data with low rewriting frequency are memorize | stored is detected. It is a flowchart which shows the flow of the process performed by one Embodiment of this invention. FIG. 7A shows a flash memory in which a physical block storing a rewrite mark and a physical block storing a change count value are mixed. FIG. 7B shows a process flow regarding the first example in which the rewrite mark is updated. FIG. 8A shows a flash memory in which a physical block storing a rewrite mark and a physical block storing a switching count value are mixed. FIG. 8B shows the flow of processing relating to the second example in which the rewrite mark is updated. FIG. 9A shows the flow of processing relating to the third example in which the rewrite mark is updated. FIG. 9B shows the flow of processing relating to the fourth example in which the rewrite mark is updated.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Flash memory system, 2 ... Flash memory, 3 ... Memory controller, 6 ... Microprocessor

Claims (11)

A memory controller that controls access to a flash memory that is erased in units of physical blocks based on an access instruction given from a host system,
Logical block allocating means for allocating a logical block composed of a plurality of sectors in the logical address space on the host system side to the physical block;
Address translation table management means for managing an address translation table indicating a correspondence relationship between the logical block and the physical block set by the logical block allocation means;
Table storage that is the physical block that is the storage destination of the address conversion table when the correspondence relationship between at least some of the logical blocks and the physical block in the address conversion table is changed by the address conversion table management unit Address conversion table storage means for storing the address conversion table in a block;
A table storage block management means for newly allocating another physical block as the table storage block when there is no more free space for storing the address conversion table in the table storage block;
When the table storage block management means assigns a new table storage block, the previous count value that is the count value that matches the count value stored in the table storage block that has no free space Count information writing means for writing the latest count value, which is the updated count value, into the physical block newly assigned as the table storage block;
Version number information determining means for determining version number information to be written in the physical block to which the logical block is newly allocated based on the latest count value;
Version number information writing means for writing the version number information determined by the version number information determining means into the physical block to which the logical block is newly assigned;
Determining means for determining whether to transfer the data stored in the physical block to another physical block based on the version number information written in the physical block;
Data transfer means for transferring data stored in the physical block that is the object of the positive determination to another physical block when a positive determination is made by the determination means;
A memory controller. A memory controller that controls access to a flash memory that is erased in units of physical blocks based on an access instruction given from a host system,
Logical block allocating means for allocating a logical block composed of a plurality of sectors in the logical address space on the host system side to the physical block;
Address translation table management means for managing an address translation table indicating a correspondence relationship between the logical block and the physical block set by the logical block allocation means;
Table storage that is the physical block that is the storage destination of the address conversion table when the correspondence relationship between at least some of the logical blocks and the physical block in the address conversion table is changed by the address conversion table management unit Address conversion table storage means for storing the address conversion table in a block;
A table storage block management means for newly allocating another physical block as the table storage block when there is no more free space for storing the address conversion table in the table storage block;
When the physical block allocated as the table storage block changes, the management information indicating the physical block allocated as the table storage block is the management information that is the physical block of the storage destination of the management information Management information storage means to be stored in the block;
Management information block management means for newly allocating another physical block as the management information block when there is no free space for storing the management information in the management information block;
When the management information block management means assigns a new management information block, the count value immediately before is a count value that matches the count value stored in the management information block that has no free space. Count information writing means for writing the latest count value, which is the updated count value, into the physical block newly assigned as the management information block;
Version number information determining means for determining version number information to be written in the physical block to which the logical block is newly allocated based on the latest count value;
Version number information writing means for writing the version number information determined by the version number information determining means into the physical block to which the logical block is newly assigned;
Determining means for determining whether to transfer the data stored in the physical block to another physical block based on the version number information written in the physical block;
Data transfer means for transferring data stored in the physical block that is the object of the positive determination to another physical block when a positive determination is made by the determination means;
A memory controller. A memory controller that controls access to a flash memory that is erased in units of physical blocks based on an access instruction given from a host system,
Block management means for managing a correspondence relationship between a logical block composed of a plurality of sectors in the logical address space on the host system side and the physical block;
Means for searching for the physical block in the erased state in the flash memory, the free block searching means for determining in a predetermined order whether or not the physical block in the flash memory is in an erased state;
Logical block allocation means for allocating the logical block to the physical block in the erased state detected by the free block search means;
Version number information management means for updating the version number information to be written in the physical block to which the logical block is assigned each time the search in the predetermined order in the empty block search means circulates a predetermined number of times,
Version number information writing means for writing the version number information to the physical block to which the logical block is newly assigned;
Determining means for determining whether to transfer the data stored in the physical block to another physical block based on the version number information written in the physical block;
Data transfer means for transferring data stored in the physical block that is the object of the positive determination to another physical block when a positive determination is made by the determination means;
A memory controller. A memory controller that controls access to a flash memory that is erased in units of physical blocks based on an access instruction given from a host system,
Block management means for managing a correspondence relationship between a logical block composed of a plurality of sectors in the logical address space on the host system side and the physical block;
Count means for updating the count value each time the logical block is newly assigned to the physical block, and version number information to be written to the physical block to which the logical block is assigned when the count value reaches a predetermined value Version information management means for updating
Version number information writing means for writing the version number information to the physical block to which the logical block is newly assigned;
Determining means for determining whether to transfer the data stored in the physical block to another physical block based on the version number information written in the physical block;
Data transfer means for transferring data stored in the physical block that is the object of the positive determination to another physical block when a positive determination is made by the determination means;
A memory controller. The version number information is information indicating at least three types of version numbers prepared in advance that circulate in a predetermined order;
The physical block to be affirmatively determined is a physical block in which the version number information that is a predetermined order or more before the current version number information is stored.
The memory controller according to claim 1. A memory controller according to any one of claims 1 to 5;
Flash memory accessed by the memory controller;
A flash memory system. A flash memory control method for controlling access to a flash memory that is erased in units of physical blocks based on an access instruction given from a host system,
A logical block allocation step for allocating a logical block composed of a plurality of sectors in the logical address space on the host system side to the physical block;
An address translation table management step for managing an address translation table indicating a correspondence relationship between the logical block and the physical block set by the logical block allocation step;
When the address translation table management step changes the correspondence between at least some of the logical blocks and the physical block in the address translation table, the table is the physical block that is the destination of the address translation table. An address conversion table storage step for storing the address conversion table in a block;
A table storage block management step for newly allocating another physical block as the table storage block when there is no more free space in the table storage block for storing the address conversion table;
When a new table storage block is allocated by the table storage block management step, the count value immediately before is a count value that matches the count value stored in the table storage block that has no free space. A count information writing step of writing the latest count value, which is the updated count value, into the physical block newly assigned as the table storage block;
A version number information determining step for determining version number information to be written in the physical block to which the logical block is newly allocated based on the latest count value;
A version number information writing step of writing the version number information determined in the version number information determination step into the physical block to which the logical block is newly assigned;
A determination step of determining whether or not to transfer data stored in the physical block to another physical block based on the version number information written in the physical block;
A data transfer step of transferring data stored in the physical block to be subjected to the positive determination to another physical block when a positive determination is made by the determination step;
A method for controlling a flash memory. A flash memory control method for controlling access to a flash memory that is erased in units of physical blocks based on an access instruction given from a host system,
A logical block allocation step for allocating a logical block composed of a plurality of sectors in the logical address space on the host system side to the physical block;
An address translation table management step for managing an address translation table indicating a correspondence relationship between the logical block and the physical block set by the logical block allocation step;
When the address translation table management step changes the correspondence between at least some of the logical blocks and the physical block in the address translation table, the table is the physical block that is the destination of the address translation table. An address conversion table storage step for storing the address conversion table in a block;
A table storage block management step for newly allocating another physical block as the table storage block when there is no more free space in the table storage block for storing the address conversion table;
When the physical block allocated as the table storage block changes, the management information indicating the physical block allocated as the table storage block is the management information that is the physical block of the storage destination of the management information A management information storage step to be stored in the block;
A management information block management step for newly assigning another physical block as the management information block when there is no more free space in the management information block for storing the management information;
When a new management information block is allocated by the management information block management step, a count value immediately before that is a count value that matches a count value stored in the management information block that has no free space A count information writing step of updating and writing the latest count value, which is the updated count value, to the physical block newly assigned as the management information block;
A version number information determining step for determining version number information to be written in the physical block to which the logical block is newly allocated based on the latest count value;
A version number information writing step of writing the version number information determined in the version number information determination step into the physical block to which the logical block is newly assigned;
A determination step of determining whether or not to transfer data stored in the physical block to another physical block based on the version number information written in the physical block;
A data transfer step of transferring data stored in the physical block to be subjected to the positive determination to another physical block when a positive determination is made by the determination step;
A method for controlling a flash memory. A flash memory control method for controlling access to a flash memory that is erased in units of physical blocks based on an access instruction given from a host system,
A block management step for managing the correspondence between a logical block composed of a plurality of sectors in the logical address space on the host system side and the physical block;
A search for the physical block in the erased state in the flash memory, and a free block search step for determining in a predetermined order whether or not the physical block in the flash memory is in an erased state;
A logical block allocation step of allocating the logical block to the physical block in the erased state detected in the empty block search step;
A version number information management step for updating version number information to be written in the physical block to which the logical block is allocated each time the search in the predetermined order in the empty block search step circulates a predetermined number of times,
A version number information writing step for writing the version number information to the physical block to which the logical block is newly assigned;
A determination step of determining whether or not to transfer data stored in the physical block to another physical block based on the version number information written in the physical block;
A data transfer step of transferring data stored in the physical block to be subjected to the positive determination to another physical block when a positive determination is made by the determination step;
A method for controlling a flash memory. A flash memory control method for controlling access to a flash memory that is erased in units of physical blocks based on an access instruction given from a host system,
A block management step for managing the correspondence between a logical block composed of a plurality of sectors in the logical address space on the host system side and the physical block;
A count step of updating a count value each time the logical block is newly assigned to the physical block, and version number information to be written to the physical block to which the logical block is assigned when the count value reaches a predetermined value Version number information management step to update,
A version number information writing step for writing the version number information to the physical block to which the logical block is newly assigned;
A determination step of determining whether or not to transfer data stored in the physical block to another physical block based on the version number information written in the physical block;
A data transfer step of transferring data stored in the physical block to be subjected to the positive determination to another physical block when a positive determination is made by the determination step;
A method for controlling a flash memory. The version number information is information indicating at least three types of version numbers prepared in advance that circulate in a predetermined order;
The physical block to be affirmatively determined is a physical block in which the version number information that is a predetermined order or more before the current version number information is stored.
The method for controlling a flash memory according to claim 7.

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