JP4687720B2 - 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.

  Conventionally, data corresponding to each logical page given from the host system is not stored in the host system without fixing the correspondence between the logical page included in the logical block and the physical page included in the physical block corresponding to the logical block. There is known a method of writing to physical pages in a physical block in the order given by (see, for example, Patent Document 1). In such a writing method, since data given from the host system is written in order from the head to a page in which data in the physical block is not written, data can be easily rewritten. On the other hand, when data is read, since the correspondence between the logical page and the physical page is not fixed, it is necessary to grasp the correspondence between the logical page and the physical page.

JP 2005-196736

  If information specifying the logical page (or logical sector area) such as the number of the logical page (or logical sector area) corresponding to the redundant area of each physical page is written, the logical page (or logical page) is written based on this information. The correspondence relationship between the sector area) and the physical page (or physical sector area) can be grasped.

  However, the information specifying the logical page (or logical sector area) is sequentially read from each physical page where data is written, and the correspondence between the logical page (or logical sector area) and the physical page (or physical sector area) is determined. To grasp, processing efficiency is not good.

  Therefore, the present invention provides a logical page (or logical sector area) and a physical page (or physical sector) that can efficiently grasp the correspondence between the logical page (or logical sector area) and the physical page (or physical sector area). The purpose is to provide the management technology of the correspondence relationship of (region).

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 including a plurality of physical sector areas, based on an access instruction given from a host system. And
A block management means for managing a correspondence relationship between a logical block composed of a plurality of logical sector areas and the physical block;
Empty sector area search means for searching for the beginning of the physical sector area in which data in the physical block corresponding to the logical block to which the logical access area specified as the area to be accessed by the access instruction belongs is not written;
A series of data instructed to be written to the logical access area by the access instruction is transferred from the head physical sector area to which the data detected by the free sector area search means is not written, to the physical address at the end. Data writing means for sequentially writing toward the sector area;
The first area, which is the logical sector area corresponding to the head data of a series of data instructed to be written to the logical access area by the access instruction, corresponds to the logical block to which the logical access area belongs. Judgment means for judging whether it is an area following the second area which is the logical sector area corresponding to the data stored in the last physical sector area in which the data in the physical block is written When,
The physical sector area in the physical block in which the series of data has been written by the data writing means when the determining means determines that the first area is not an area following the second area And sector management information indicating a correspondence relationship with the logical sector area in the logical block corresponding to the physical block, the physical sector area next to the physical sector area in which the end data of the series of data is written And sector management information writing means. The determination unit determines that the first area is not an area subsequent to the second area when the data stored in the physical sector area at the end is the sector management information.

  In a preferred embodiment, the determination means determines whether or not the first area is an area following the second area based on a serial number assigned to the logical sector area in the logical block. When the serial number corresponding to the first area is not the next number of the serial number corresponding to the second area, it is determined that the first area is not an area subsequent to the second area.

  In a preferred embodiment, the data stored in the physical sector area in the physical block corresponding to the logical block to which the logical access area specified by the access instruction belongs is written into the data in the physical block. And a data reading means for reading out based on the sector management information stored in the last physical sector area.

  In a preferred embodiment, when the sector management information is not stored in the physical block corresponding to the logical block to which the logical access area belongs, the data stored in the physical block is stored in the physical block. The data corresponding to the logical sector area after the logical sector area corresponding to the data stored in the head physical sector area is regarded as being written in the order of the logical sector area, and data is read. .

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 including a plurality of physical pages 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 logical pages and the physical block;
Empty page search means for searching for the top of the physical page in which data in the physical block corresponding to the logical block to which the logical access page designated as the logical page to be accessed belongs by the access instruction belongs,
A series of data instructed to be written to the logical access page by the access instruction is transferred from the first physical page to which the data detected by the empty page search unit is not written to the last physical page. Data writing means for sequentially writing toward the
The first page which is the logical page corresponding to the first data of a series of data instructed to be written to the logical access page by the access instruction corresponds to the logical block to which the logical access page belongs. Determining means for determining whether the page is subsequent to the second page that is the logical page corresponding to the data stored in the last physical page in which data in the physical block is written;
When the determining means determines that the first page is not a page following the second page, the physical page in the physical block in which the series of data has been written by the data writing means Page management information for writing page management information indicating a correspondence relationship with the logical page in the logical block corresponding to the physical block to the physical page next to the physical page in which the end data of the series of data is written Information writing means. The determination unit determines that the first page is not a page subsequent to the second page when the data stored in the physical page at the end is the page management information.

  In a preferred embodiment, the determination means determines whether the first page is a page subsequent to the second page based on a serial number assigned to the logical page in the logical block. When the serial number corresponding to the first page is not the next number of the serial number corresponding to the second page, it is determined that the first page is not a page subsequent to the second page.

  In a preferred embodiment, data stored in the physical page in the physical block corresponding to the logical block to which the logical access page specified by the access instruction belongs is written into the data in the physical block. And a data reading means for reading based on the page management information stored in the last physical page.

  In a preferred embodiment, when the page management information is not stored in the physical block corresponding to the logical block to which the logical access page belongs, the data reading means stores data stored in the physical block as follows: The data corresponding to the logical page after the logical page corresponding to the data stored in the first physical page in the physical block is regarded as being written in the order of the logical pages, and the data is read. I do.

  A flash memory system according to a third aspect of the present invention comprises a memory controller according to the first or second aspect and a flash memory accessed by the memory controller.

A flash memory control method according to a fourth aspect of the present invention is a flash memory control method in which erasure is performed in units of physical blocks including a plurality of physical sector areas,
A block management step for managing a correspondence relationship between a logical block composed of a plurality of logical sector areas and the physical block;
A free sector area search step for searching for the beginning of the physical sector area in which data in the physical block corresponding to the logical block to which the logical access area designated as the access target area by the access instruction belongs is not written;
A series of data instructed to be written to the logical access area by the access instruction is transferred from the first physical sector area to which the data detected by the free sector area search step is not written to the last physical sector. A data writing step of sequentially writing toward the sector area;
The first area, which is the logical sector area corresponding to the head data of a series of data instructed to be written to the logical access area by the access instruction, corresponds to the logical block to which the logical access area belongs. A determination step of determining whether or not it is an area following the second area which is the logical sector area corresponding to the data stored in the physical sector area at the end in which the data in the physical block is written When,
When the determination step determines that the first area is not an area following the second area, the physical sector area in the physical block in which the series of data has been written by the data write step And sector management information indicating a correspondence relationship with the logical sector area in the logical block corresponding to the physical block, the physical sector area next to the physical sector area in which the end data of the series of data is written A sector management information writing step. In the determining step, when the data stored in the physical sector area at the end is the sector management information, it is determined that the first area is not an area following the second area.

A flash memory control method according to a fifth aspect of the present invention is a flash memory control method in which erasing is performed in units of physical blocks including a plurality of physical pages based on an access instruction given from a host system.
A block management step for managing a correspondence relationship between a logical block composed of a plurality of logical pages and the physical block;
A free page search step of searching for the top of the physical page in which data in the physical block corresponding to the logical block to which the logical access page designated as the logical page to be accessed by the access instruction belongs is not written;
A series of data instructed to be written to the logical access page by the access instruction is transferred from the first physical page to which the data detected by the empty page search step is not written to the last physical page. A data writing step of sequentially writing toward the
The first page which is the logical page corresponding to the first data of a series of data instructed to be written to the logical access page by the access instruction corresponds to the logical block to which the logical access page belongs. A determination step of determining whether or not the page is subsequent to the second page which is the logical page corresponding to the data stored in the last physical page in which data in the physical block is written;
When the determination step determines that the first page is not a page subsequent to the second page, the physical page in the physical block in which the series of data has been written by the data writing step Page management information for writing page management information indicating a correspondence relationship with the logical page in the logical block corresponding to the physical block to the physical page next to the physical page in which the end data of the series of data is written An information writing step. In the determination step, when the data stored in the physical page at the end is the page management information, it is determined that the first page is not a page subsequent to the second page.

  Correspondence between logical page (or logical sector area) and physical page (or physical sector area) that can efficiently grasp the correspondence between logical page (or logical sector area) and physical page (or physical sector area) Management technology can be provided.

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

  <First Embodiment>

  FIG. 1 is a block diagram schematically showing a flash memory system 1 according to the first 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. In the work area 8, for example, an address conversion table (described later) indicating the correspondence between logical blocks and physical blocks is stored.

  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 in accordance with 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 (physical 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, and a block status (flag).

  FIG. 2 shows a storage area included in one physical page of the NAND flash memory used in this embodiment.

  The user area 25 is an area for storing data given from the host system 4. The redundant area 26 is an area for storing additional data such as an error correction code (ECC), logical address information, and a block status (flag).

  In the present embodiment, as shown in FIG. 2, the user area 25 is used by being divided into one sector (for example, 512 bytes) physical sector area 60 (60a-60d). The redundant area 26 is divided into a common redundant area 50 having a predetermined size (for example, 8 bytes) and a divided redundant area 70 (70a to 70d) having a predetermined size (for example, 14 bytes). Information managed for each physical block such as logical address information and block status (flag) is written in the common redundant area 50 corresponding to the first physical page of each physical block.

  The four physical sector areas 60a-60d and the four divided redundant areas 70a-70d have a one-to-one correspondence set in advance. In this embodiment, the physical sector area 60a is the divided redundant area 70a, the physical sector area 60b is the divided redundant area 70b, the physical sector area 60c is the divided redundant area 70c, and the physical sector area 60d is the divided redundant area 70d. It corresponds. In the divided redundant areas 70a to 70d, information managed for each physical sector area 60 (60a to 60d) such as an error correction code added to data stored in the corresponding physical sector areas 60a to 60d is written. It is.

  As described above, in a NAND flash memory in which one physical page is configured by a user area of m sectors and one physical block is configured by n physical pages, one physical block is m × It can also be handled as a NAND flash memory composed of n physical sector areas (areas per sector). That is, the NAND flash memory used in the present embodiment can be handled as a NAND flash memory composed of 256 physical sector areas (areas of one sector unit). In the following description, a serial number assigned to a physical sector area in a physical block is referred to as a physical sector number (PSN). For example, when one physical block is composed of 256 physical sector areas, # 0 to # 255 are assigned as PSNs to 256 physical sector areas in each physical block.

  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, logical address information is stored in the redundant area 26 (in the common redundant area 50 corresponding to the first physical page). Not.

  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.

  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). In the address management performed in the memory controller, a logical block is formed by a plurality of logical sector areas, and one or a plurality of physical blocks are allocated to the logical block.

  In the present embodiment, as shown in FIG. 3, a group of 256 logical sector areas with continuous LBAs is defined as a logical block, and a serial number is assigned to this logical block. Hereinafter, a serial number assigned to a logical block is referred to as a logical block number (LBN). 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. . 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 logical group in which a plurality of logical blocks are collected is formed. Hereinafter, a serial number assigned to a logical group is referred to as a logical group number (LGN). In the example of FIG. 3, logical groups are formed by sequentially allocating logical blocks having consecutive LBNs to different logical groups. For example, the logical block of LBN # 0 is the logical group of LGN # 0, the logical block of LBN # 1 is the logical group of LGN # 1, the logical block of LBN # 2 is the logical group of LGN # 2, and so on. Sort to # 7 logical group. Similarly, the logical block of LBN # 8 is assigned to the logical group of LGN # 0, the logical block of LBN # 9 is assigned to the logical group of LGN # 1, and the logical block of LBN # 10 is assigned to the logical group of LGN # 2. Go. In this way, 8 logical groups consisting of 1000 logical blocks are formed.

  This logical group is simply a unit for creating an address translation table, and any logical block may be assigned to any physical block.

  This address conversion table is a table describing the correspondence between logical blocks and physical blocks, and may be a table including the correspondence between all logical blocks and physical blocks. In this embodiment, a logical group A table is created in units. This address conversion table is stored in the flash memory 2. In addition, in order to manage the area in the logical block and the area in the physical block that have a correspondence relationship, the correspondence relation between the logical sector area and the physical sector area 60 is grasped by a method described later (note that the second sector described later) In the embodiment, the correspondence between a logical page (described later) and a physical page is grasped).

  Note that the physical blocks in the flash memory include innate defective blocks that are defective from the time of shipment. Furthermore, even if a physical block is a non-defective product at the time of shipment, there is a physical block (acquired defective block) that deteriorates after use and becomes a defective block. Therefore, in this embodiment, 8192 physical blocks are assigned to 8000 logical blocks.

  In the first embodiment, the correspondence between 256 logical sector areas included in a logical block and 256 physical sector areas 60 included in a physical block is managed in units of sectors. One physical page includes four physical sector areas 60. The NAND flash memory according to the first embodiment is a NAND flash memory that can execute data writing for each physical page separately for each physical sector area 60. That is, data writing to the four physical sector areas 60 included in one physical page can be executed four times.

  In the write processing of the first embodiment, the host system 4 writes a command code indicating a write command to the command register R1, writes the number of sectors of data to be written to the sector number register R2, and writes to the LBA register R3. The LBA corresponding to the top data for starting writing is written. Based on the information written in the sector number register R2 and the LBA register R3, the logical access area that is the access target area is determined, and the data in the physical block corresponding to the logical block including the logical access area is written. Data given from the host system 4 is written from the head of the physical sector area 60 that is not.

  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 sector area 60 in which data in the physical block corresponding to the first logical block is not written. The data instructed to be written to the logical access area belonging to the second logical block is written to the physical sector area 60 where data in the physical block corresponding to the second logical block is not written.

  In the following description, in the data writing process of one sector or a plurality of sectors executed based on information given from the host system 4 (that is, information written in the command register R1, the sector number register R2, and the LBA register R3), The data to be written is called “a series of data”. For example, when the value written in the sector number register R2 is n (n is an integer of 1 or more), data in which LBAs for n sectors are continuous corresponds to a series of data. When the logical access area extends over a plurality of logical blocks, a series of data is divided for each logical block. For example, when the logical access area extends over two logical blocks (the first logical block and the second logical block), the number of sectors in the logical access area belonging to the first logical block is p sectors, If the number of sectors in the logical access area belonging to the logical block 2 is q sectors, even if the value written in the sector number register R2 is n (n = p + q), the series of data is a series of p sectors. The data is divided into a series of data of q sectors.

  The host system 4 indicates the address of the data to be written or the address of the data to be read by LBA. That is, the LBA discriminated based on the information written in the sector number register R2 and the LBA register R3 (when the value written in the sector number register R2 is 1), or the range where the LBA is continuous (sector number register R2 When the value written in (2) is 2 or more), the address indicating the write destination of the data to be written or the address indicating the read source of the data to be read is obtained.

Here, when the number of logical sector areas included in one logical block is 2 ⁱ (for example, 256 when i = 8), the lower i bits of the LBA (for example, lower when i = 8) 8 bits) corresponds to the serial number assigned to the logical sector area in the logical block. Hereinafter, the serial number assigned to the logical sector area in the logical block is referred to as “logical sector number (LSN)”. On the other hand, the serial number assigned to the physical sector area 60 in the physical block is referred to as “physical sector number (PSN)”. Further, the upper bits of the LBA excluding the lower i bits of the LBA (for example, the lower 8 bits when i = 8) correspond to the LBN (logical block number) described above. Therefore, it corresponds to the LBN of the LBA of the first logical sector area and the last logical sector area in the logical access area (range where the LBA continues) determined based on the information written in the sector number register R2 and the LBA register R3. If the value indicated by the bit of the part to be processed is the same, the logical access area does not extend over a plurality of logical blocks.

  Hereinafter, an outline of writing in this embodiment will be described.

  The memory controller 3 writes a series of data given together with the write instruction to the flash memory 2 in accordance with a write instruction (write command and write destination address) given from the host system 4. In this write process, a logical block to which a write-destination logical sector area belongs is specified, and a series of data is written to a physical block corresponding to the logical block (or a physical block newly allocated to the logical block). It is. A series of data is written in the physical sector area 60 in the physical block in order from the top (that is, in order from the smallest PSN). Therefore, when the memory controller 3 writes a series of data, the end of the physical sector area in which the data in the physical block is written is searched. Then, a series of data is sequentially written from the physical sector area 60 next to the last physical sector area 60. In other words, a series of data is sequentially written from the top physical sector area in which data in the physical block is not written.

  In the present embodiment, information indicating the correspondence between the logical sector area and the physical sector area 60 (hereinafter, “sector management information”) is stored in the physical sector area 60 next to the physical sector area 60 in which the end data of a series of data is written. For example, a table indicating the correspondence between the logical sector area and the physical sector area 60 is written. That is, the sector management information is written in the user area 25 (physical sector area 60) in the same manner as a series of data given from the host system 4 together with a write instruction. Accordingly, the memory controller 3 retrieves the end of the physical sector area 60 in which data in the physical block is written, and reads the sector management information from the physical sector area 60, so that the memory controller 3 associates the logical sector area with the physical sector area 60. You can understand the relationship. The sector management information in this embodiment is, for example, a table having 256 records corresponding to the logical sector numbers of 256 logical sector areas (see, for example, FIG. 5A described later).

  In this embodiment, when writing a series of data, in order to determine whether or not to write sector management information in the physical sector area 60 in the physical block to which the series of data is written, the first data of the series of data is supported. The logical sector area (hereinafter referred to as “first logical sector area”) corresponds to the data stored in the last physical sector area 60 in which the data in the physical block to which the series of data is written is written. It is determined whether it is an area following the logical sector area to be performed (hereinafter referred to as “second logical sector area”). If it is determined by this determination that the first logical sector area is an area subsequent to the second logical sector area, the sector management information is not written. On the other hand, when it is determined that the first logical sector area is not an area subsequent to the second logical sector area, the sector management information is written. That is, if the LSN in the first logical sector area is the next number after the LSN in the second logical sector area, the sector management information is not written. On the other hand, if the LSN of the first logical sector area is not the next number of the LSN of the second logical sector area, the sector management information is written. If the data stored in the last physical sector area 60 where the data in the physical block is written is sector management information, the sector management information is written without making the above determination.

  Therefore, in the case of a physical block in which sector management information is not written, a plurality of physical sector areas 60 from the first physical sector area 60 to the last physical sector area 60 in which data is written are included in the physical block. Thus, logical sector areas subsequent to the logical sector area corresponding to the data stored in the head physical sector area 60 are allocated in the LSN order (hereinafter, such a state is referred to as a logical sector having consecutive LSNs. Say "space is allocated").

  For example, the last physical sector area 60 in which data in the physical block is written is the physical sector area 60 of PSN # 63, and the physical sector area 60 of PSN # 0 to # 63 in the physical block has LSN # 8 ~. When the data corresponding to the logical sector area of # 71 is written in the LSN order, the sector management information is not written in the physical block.

  In the actual writing process, the following two determinations are made when writing a series of data.

  First, the data stored in the last physical sector area 60 where the data in the physical block of the write destination is written is data written as a series of data or data written as sector management information. A determination is made whether there is. Here, when the data stored in the physical sector area 60 at the end is sector management information, the “state in which a logical sector area having continuous LSNs is already allocated” has not been maintained, so No judgment is made.

  Next, if the data stored in the last physical sector area 60 is not sector management information, the data written in the physical sector area 60 next to the last physical sector area 60 (a series of data written in the current writing process). It is determined whether the LSN of the logical sector area corresponding to the first data of the data is the next number of the LSN of the logical sector area corresponding to the data stored in the last physical sector area 60. If the data stored in the last physical sector area 60 is not sector management information, the already written data is in a “state in which a logical sector area with continuous LSN is allocated”. Whether a state can be maintained when a series of data is written in the writing process is a problem. Here, the LSN of the logical sector area corresponding to the head data of the series of data written in the current writing process is the logical sector area corresponding to the data stored in the last physical sector area 60 where the data is written. If it is the number next to the LSN, even after writing this series of data, the “state in which logical sector areas with continuous LSNs are allocated” is maintained. Therefore, the LSN of the logical sector area corresponding to the head data of the series of data written in the current writing process is the LSN of the logical sector area corresponding to the data stored in the last physical sector area 60 where the data is written. If it is the next number, sector management information is not written.

  In the present embodiment, in order to determine the LSN of the logical sector area corresponding to the data stored in the physical sector area 60, as shown in FIG. The LSN of the logical sector area corresponding to the head data is written into the divided redundant area 70 corresponding to. Accordingly, at least the LSN of the logical sector area corresponding to the data stored in the head physical sector area 60 in the physical block is written in the divided redundant area 70 corresponding to the head physical sector area 60.

  When making the above determination, data is written based on the LSN of the logical sector area corresponding to the data written in the top physical sector area 60 and the PSN of the last physical sector area 60 in which the data is written. The LSN of the logical sector area corresponding to the data stored in the last physical sector area 60 is obtained. Specifically, for example, by adding the PSN value of the last physical sector area where data is written to the LSN value of the logical sector area written to the top physical sector area 60 and corresponding to the data, The LSN of the logical sector area corresponding to the data stored in the last physical sector area where data is written is obtained. The memory controller 3 writes the LSN of the logical sector area corresponding to the data written in the physical sector area 60 in the divided redundant area 70 corresponding to the physical sector area 60 in which the end data of the series of data is written. It may be.

  In the present embodiment, in order to detect a case where the writing process is terminated in the middle of the writing due to power interruption or the like, the writing process is normal in the divided redundant area 70 corresponding to the physical sector area 60 in which the end data of the series of data is written. An end mark, which is information indicating the end, is written. However, when the sector management information is written, the divided redundant area 70 corresponding to the physical sector area 60 in which the sector management information is written, that is, the next to the physical sector area 60 in which the end data of a series of data is written. An end mark is written in the divided redundant area 70 corresponding to the physical sector area 60. By doing so, the memory controller 3 writes the sector management information when the write processing is completed after the series of data has been written and before the sector management information is written due to power interruption or the like. Misunderstanding that this is the case can be avoided.

  If the “state where logical sector areas with continuous LSN are allocated” is not maintained, the data stored in the physical sector area 60 at the end where the data in the physical block is written is the logical sector. It must be the latest sector management information regarding the correspondence between the area and the physical sector area 60. Accordingly, when a series of data is written to a physical block that does not maintain the “state in which logical sector regions having continuous LSNs are allocated”, the sector management information is updated. The updated sector management information is written in the physical sector area 60 next to the physical sector area 60 in which the end data of the series of data is written. In updating the sector management information, the contents of the sector management information are updated for a portion corresponding to a series of data to be written. In this embodiment, in order to be able to determine whether or not the data stored in the last physical sector area 60 in which the data in the physical block is written is sector management information, the sector management information is A flag (hereinafter referred to as “management flag”) indicating that the sector management information has been written is written in the divided redundant area 70 corresponding to the written physical sector area 60. As a result, the memory controller 3 determines whether or not the last physical sector area depends on whether or not the management flag is stored in the divided redundant area 70 corresponding to the last physical sector area 60 in which data in the physical block is written. Whether the data stored in 60 is sector management information or not can be determined.

  Further, when a plurality of series of data is continuously written in the same physical block, the work area 8 is not read out from the last physical sector area 60 in which the data in the physical block is written. The sector management information held in the file may be used as it is.

  When the capacity of data given from the host system 4 together with the write instruction is larger than the capacity of the empty sector area in the write destination physical block (first physical block), the memory controller 3 determines the end of the physical block. The data given from the host system 4 is written up to the physical sector area 60 one sector before the physical sector area 60, and the correspondence between the logical sector area and the physical sector area 60 at that time is written in the last physical sector area 60 Write sector management information indicating the relationship. The remaining data is written to the physical sector area 60 in another newly allocated physical block (second physical block). That is, when all the data corresponding to each logical sector area in the logical block from the first physical sector area 60 to the last physical sector area 60 in the first physical block is written in LSN order (first logical block Sector management information is written in the last physical sector area 60 (except when data is written in the order of LSN from the data corresponding to the sector area).

  When writing a series of data, if the empty sector area in the first physical block is only the last physical sector area 60, the series of data is not written in the last physical sector area 60. Writing of a series of data is started from the top physical sector area 60 of the second physical block.

  Hereinafter, a specific example of the writing process in the present embodiment will be described with reference to FIGS. 4 and 5. As described above, a series of data is written in order from the smallest PSN. In the following description, a series of data written in the nth (n is a natural number) is referred to as an “nth series of data”.

  First, based on the first write instruction given from the host system 4, 16 logical sector areas of LBA # 16- # 31 (LSN # 16- # 31 in the logical block of LBN # 0) are used as logical access areas. Are determined). Since there is no physical block corresponding to the logical block to which this logical access area belongs, a new physical block is assigned to this logical block. Since no data has been written yet in this physical block, the first physical sector area 60 (PSN # 0 physical sector area) in the physical block is used as the first physical sector area 60 in which no data in the physical block is written. 60) is specified. From this top physical sector area 60 (PSN # 0 physical sector area 60), a first series of data write processing corresponding to the first write instruction is started. As a result, the first series of data corresponding to the 16 logical sector areas of LSN # 16- # 31 is written to the 16 physical sector areas 60 of PSN # 0- # 15. In addition, in the divided redundant area 70 corresponding to the physical sector area 60 (PSN # 0 physical sector area 60) where the first data of the first series of data is written, the LSN ( The value “# 16” of the LSN of the first logical sector area among the 16 logical sector areas of LSN # 16- # 31 is written (see FIG. 4A).

  Since the first series of data is the first series of data to be written to this physical block, at the stage where the first series of data is written, “the logical sector area where the LSN is continuous is allocated. Is maintained. For this reason, sector management information is not written in the physical sector area 60 next to the physical sector area 60 (PSN # 15 physical sector area 60) in which the end data of the first series of data is written, and the PSN # 15 An end mark (EM (End Mark)) is written in the divided redundant area 70 corresponding to the physical sector area 60.

  Next, based on the second write instruction given from the host system 4, 16 logical sector areas LBA # 32- # 47 (LSN # 32- # in the logical block of LBN # 0) are used as logical access areas. 47 logical sector areas) are identified. Further, the physical sector area 60 of PSN # 15 is specified as the last physical sector area 60 in which data in the physical block is written. A second series corresponding to the second write instruction from the physical sector area 60 (PSN # 16 physical sector area 60) next to the identified end physical sector area 60 (PSN # 15 physical sector area 60). Writing of data is started. As a result, the second series of data corresponding to the 16 logical sector areas of LSN # 32- # 47 is written into the 16 physical sector areas 60 of PSN # 16- # 31. Also, the LSN of the logical sector area corresponding to the head data is added to the divided redundant area 70 corresponding to the physical sector area 60 (PSN # 16 physical sector area 60) in which the head data of the second series of data is written. The value “# 32” of (the LSN of the first logical sector area among the 16 logical sector areas of LSN # 32- # 47) is written (see FIG. 4A).

  Whether or not the data stored in the last physical sector area 60 (physical sector area 60 of PSN # 15) in which data in the physical block is written is sector management information when the writing process is started Is judged. Since the data stored in the physical sector area 60 of PSN # 15 is not sector management information, the LSN of the first logical sector area (the logical sector area corresponding to the first data of the second series of data) is the second It is determined whether it is the next number of the LSN of the logical sector area (the logical sector area corresponding to the data stored in the last physical sector area 60 where the data is written). More specifically, the LSN value “# 16” written in the divided redundant area 70 corresponding to the top physical sector area 60 is added to the PPN value “#” of the last physical sector area 60 in which data is written. “# 31”, which is a value obtained by adding “15”, is obtained as the LSN of the second logical sector area. On the other hand, since the LSN of the first logical sector area is “# 32”, it is determined that the LSN of the first logical sector area is the next number after the LSN of the second logical sector area. As described above, when the LSN of the first logical sector area is the next number of the LSN of the second logical sector area, even after writing a series of data, “the logical sector area where the LSN continues is allocated. "State" is maintained.

  In this writing process, the “state in which logical sector areas having continuous LSNs are allocated” is maintained, so that the physical sector area 60 (PSN # 31 physical sector) in which the tail data of the second series of data is written is maintained. Sector management information is not written in the physical sector area 60 next to the area 60), and an end mark is written in the divided redundant area 70 corresponding to the physical sector area 60 of PSN # 31.

  As shown in FIG. 4A, the second series of data and the fourth series of data respectively corresponding to the third write instruction and the fourth write instruction given from the host system 4 are also the second A writing process similar to a series of data is executed.

  Next, based on the fifth write instruction given from the host system 4, 32 logical sector areas LBA # 0- # 31 (LSN # 0- # in the logical block of LBN # 0) are used as logical access areas. 31 logical sector areas) are identified. Further, the physical sector area 60 of PSN # 95 is specified as the last physical sector area 60 in which data in the physical block is written. The fifth series corresponding to the fifth write instruction from the physical sector area 60 (PSN # 96 physical sector area 60) next to the identified end physical sector area 60 (PSN # 95 physical sector area 60). Writing of data is started. As a result, the fifth series of data corresponding to the 32 logical sector areas of LSN # 0 to # 31 is written to the 32 physical sector areas 60 of PSN # 96 to # 127. In addition, in the divided redundant area 70 corresponding to the physical sector area 60 (PSN # 96 physical sector area 60) in which the top data of the fifth series of data is written, the LSN ( The value “# 96” of the LSN of the leading logical sector area among the 32 logical sector areas of LSN # 96- # 127 is written (see FIG. 4A).

Whether or not the data stored in the last physical sector area 60 (physical sector area 60 of PSN # 31) where the data in the physical block is written is sector management information when the writing process is started Is judged. Since the data stored in the physical sector area 60 of PSN # 31 is not sector management information, the LSN of the first logical sector area (the logical sector area corresponding to the first data of the fifth series of data) is the second It is determined whether it is the next number of the LSN of the logical sector area (the logical sector area corresponding to the data stored in the last physical sector area 60 where the data is written). Specifically, the LSN value “# 16” written in the divided redundant area 70 corresponding to the top physical sector area 60 is added to the PPN value “# 95” in the last physical sector area where data is written. “# 111” that is a value obtained by adding “” is obtained as the LSN of the second logical sector area. On the other hand, the LSN of the first logical sector area
Since “# 0”, it is determined that the LSN of the first logical sector area is not the next number of the LSN of the second logical sector area. As described above, when the LSN of the first logical sector area is not the next number of the LSN of the second logical sector area, after writing a series of data, “the logical sector area where the LSN continues is allocated. Is not maintained.

  In this writing process, the “state in which logical sector areas with continuous LSNs are allocated” is not maintained, so that the memory controller 3 is stored in the physical block when the fifth series of data writing is completed. Sector management information # 0 indicating the correspondence between the physical sector area 60 and the logical sector area related to valid data is created. Here, since the data stored in the last physical sector area 60 (the physical sector area 60 of PSN # 95) in which the data before the fifth series of data is written is not sector management information (PSN #) Since the management flag is not written in the divided redundant area 70 corresponding to 95 physical sector areas 60), new sector management information is created. Specifically, a table creation area having 256 records respectively corresponding to LSN # 0-255 is secured on the work area 8, and a PSN is written in each record of this table creation area. When the sector management information # 0 as shown in FIG. 5A is created, first, the LSN # written in the physical sector area 60 of PSN # 0 to # 95 as the first to fourth series of data. The PSN for data corresponding to the 16- # 111 logical sector area is written. That is, # 0- # 95 numbers (PSN values) are written in records corresponding to LSN # 16- # 111. Next, the PSN is written for the data corresponding to the logical sector area of LSN # 0-31 written to the physical sector area 60 of PSN # 96- # 127 as the fifth series of data. That is, the numbers # 96 to # 127 (PSN values) are written in the records corresponding to LSN # 0 to 31. At this time, the record corresponding to LSN # 16-31 is overwritten with the number (PSN value) of # 112- # 127, and only the correspondence between the physical sector area 60 and the logical sector area relating to valid data remains. . That is, the correspondence between the physical sector area 60 and the logical sector area related to invalid data is overwritten by the correspondence between the physical sector area 60 and the logical sector area related to valid data. Thereby, the creation process of the sector management information # 0 as shown in FIG.

  The memory controller 3 uses the created sector management information # 0 as the physical sector area 60 (PSN) next to the physical sector area 60 (physical sector area 60 of PSN # 127) in which the end data of the fifth series of data is written. Write to the physical sector area 60) of # 128. In addition, a management flag (not shown) and the above-described end mark are written in the divided redundant area 70 corresponding to the physical sector area 60 (PSN # 128 physical sector area 60) in which the sector management information # 0 is written (see FIG. 4 (B)).

  For a physical block in which sector management information has been written even once, the sector management information is written each time a series of data is written to the physical block. This is because the physical block in which the sector management information is written even once does not maintain the “state in which logical sector areas with continuous LSN are allocated”.

  Next, based on the sixth write instruction given from the host system 4, 16 logical sector areas LBA # 16- # 31 (LSN # 16- # in the logical block of LBN # 0) are used as logical access areas. 31 logical sector areas) are identified. Further, the physical sector area 60 of PSN # 128 is specified as the last physical sector area 60 in which data in the physical block is written. A sixth series corresponding to the sixth write instruction from the physical sector area 60 (physical sector area 60 of PSN # 129) next to the identified last physical sector area 60 (physical sector area 60 of PSN # 128). Writing of data is started. As a result, the sixth series of data corresponding to the 16 logical sector areas of LSN # 16- # 31 is written to the 16 physical sector areas 60 of PSN # 129- # 144. In addition, the LSN (in the logical sector area corresponding to the head data is added to the divided redundant area 70 corresponding to the physical sector area 60 (PSN # 129 physical sector area 60) in which the head data of the sixth series of data is written. The value “# 31” of the LSN of the first logical sector area among the 16 logical sector areas of LSN # 16- # 31 is written (see FIG. 4B).

  Whether or not the data stored in the last physical sector area 60 (physical sector area 60 of PSN # 128) in which data in the physical block is written is the sector management information when starting the writing process Is judged. Since the management flag is written in the divided redundant area 70 corresponding to the physical sector area 60 of PSN # 128, it is determined that the data stored in the physical sector area 60 of PSN # 128 is sector management information. This determination means that, at this point, the “state in which logical sector regions having continuous LSNs are allocated” is not maintained.

  Therefore, sector management information # 1 indicating the correspondence between the physical sector area 60 and the logical sector area when the writing of the sixth series of data is completed is created. The sector management information # 1 is created based on the sector management information # 0. That is, in this creation process, the contents of sector management information # 0 are updated for the portion corresponding to the sixth series of data. If the sector management information # 0 is not held on the work area 8, the sector management information # 0 is transferred from the physical sector area 60 of the PSN # 128 to the work area 8 in order to create the sector management information # 1. Is read out.

  Specifically, as shown in FIG. 5B, 16 physical sector areas in which a sixth series of data is written in records corresponding to LSN # 16- # 31 in sector management information # 0. PSN corresponding to 60 is written. That is, in the process of creating sector management information # 1, the number (PSN value) of # 129- # 144 is overwritten on the record corresponding to LSN # 16- # 31 of sector management information # 0. The created sector management information # 1 is the physical sector area 60 (PSN # 145 physical) next to the physical sector area 60 (PSN # 144 physical sector area 60) in which the end data of the sixth series of data is written. It is written in the sector area 60). Further, a management flag (not shown) and the above-described end flag are written in the divided redundant area 70 corresponding to the physical sector area 60 (PSN # 145 physical sector area 60) in which the sector management information # 1 is written.

  Thereafter, similarly, the seventh and eighth series of data and the sector management information # 2 and # 3 respectively corresponding to the seventh and eighth write instructions given from the host system 4 are written in the same physical block. It is.

  That is, the seventh series of data corresponding to the 16 logical sector areas of LBA # 80- # 95 (the logical sector area of LSN # 80- # 95 in the logical block of LBN # 0) is stored in the physical block. Sixteen physical sector areas 60 (PSN) after the physical sector area 60 (PSN # 146 physical sector area 60) following the last physical sector area 60 (PSN # 145 physical sector area 60) in which data is written Is written in the physical sector area 60 of # 146-161 (see FIG. 4B). In addition, in the divided redundant area 70 corresponding to the physical sector area 60 (PSN # 146 physical sector area 60) in which the top data of the seventh series of data is written, the LSN ( A value “# 80” of the LSN of the first logical sector area among the 16 logical sector areas of LSN # 80- # 95 is written. Further, based on the sector management information # 1 stored in the last physical sector area 60 (the physical sector area 60 of PSN # 145) where the data before the seventh series of data is written, Management information # 2 is created. Specifically, as shown in FIG. 5C, 16 physical sector areas in which a seventh series of data is written in records corresponding to LSN # 80- # 95 in the sector management information # 1. # 146-161 which is PSN corresponding to 60 is overwritten. The sector management information # 2 created in this way is the physical sector area 60 (PSN) next to the physical sector area 60 (PSN # 161 physical sector area 60) in which the end data of the seventh series of data is written. It is written in the physical sector area 60) of # 162. In addition, a management flag (not shown) and the above-described end flag are written in the divided redundant area 70 corresponding to the physical sector area 60 (PSN # 162 physical sector area 60) in which the sector management information # 2 is written.

  Next, an eighth series of data corresponding to the 32 logical sector areas of LBA # 96- # 127 (the logical sector area of LSN # 96- # 127 in the logical block of LBN # 0) is stored in the physical block. 32 physical sector areas 60 (after the physical sector area 60 (PSN # 163 physical sector area 60)) following the physical sector area 60 (PSN # 162 physical sector area 60) to which the last data is written. It is written in the physical sector area 60) of PSN # 163-194 (see FIG. 4B). In addition, in the divided redundant area 70 corresponding to the physical sector area 60 (PSN # 163 physical sector area 60) in which the top data of the eighth series of data is written, the LSN ( A value “# 96” of the LSN of the first logical sector area among the 32 logical sector areas of LSN # 96- # 127 is written. Further, based on the sector management information # 2 stored in the last physical sector area 60 (the physical sector area 60 of PSN # 162) where the data before the eighth series of data is written is written Management information # 3 is created. Specifically, as shown in FIG. 5D, 32 physical sector areas in which an eighth series of data is written in records corresponding to LSN # 96- # 127 in the sector management information # 2. # 163-194 which is PSN corresponding to 60 is overwritten. The sector management information # 3 created in this way is the physical sector area 60 (PSN) next to the physical sector area 60 (PSN # 194 physical sector area 60) in which the tail data of the eighth series of data is written. It is written in the physical sector area # 195). Further, a management flag (not shown) and the above-described end flag are written in the divided redundant area 70 corresponding to the physical sector area 60 (PSN # 195 physical sector area 60) in which the sector management information # 3 is written.

  After that, when data stored in each physical sector area 60 is read from the physical block, the memory controller 3 reads the physical sector area 60 (PSN # 195 physical data) at the end where the data in the physical block is written. The sector management information # 3 is read from the sector area 60), and the correspondence between the logical sector area and the physical sector area 60 is grasped based on the sector management information # 3. Here, since the sector management information # 3 written in the physical sector area 60 of PSN # 195 indicates the latest correspondence relationship between the logical sector area and the physical sector area 60, the memory controller 3 performs the sector management. The latest correspondence between the logical sector area and the physical sector area 60 can be grasped only by referring to the information # 5. That is, according to the present embodiment, the correspondence relationship between the logical sector area and the physical sector area 60 can be grasped efficiently.

  When data is read from the physical block between the time when the first series of data is written and before the time when the fifth series of data is written (that is, when no sector management information is written) The memory controller 3 reads the data corresponding to the logical sector area after the logical sector area (LSN # 16 logical sector area) corresponding to the data stored in the first physical sector area 60 in the physical block in the order of LSN. Therefore, it is determined that the data is written in the physical sector area 60 in the physical block, and the correspondence between the logical sector area and the physical sector area 60 is grasped. Further, the LSN of the logical sector area corresponding to the data stored in the head physical sector area 60 in the physical block is grasped by the LSN written in the divided redundant area 70 corresponding to the head physical sector area 60. Is done.

  The above is the description of the first embodiment.

  The sector management information is preferably a table indicating the correspondence between the logical sector area and the physical sector area 60 as described above, but as a modification, each series of data written in the physical block The start logical sector number (hereinafter referred to as “SLSN”) that is the logical sector number of the logical sector area corresponding to the top data of the start data and the start physical sector that is the physical sector number of the physical sector area 60 in which the top data is written Information indicating a sector number (hereinafter referred to as “SPSN”) and the number of sectors of the series of data (hereinafter referred to as “SCNT”) may be used. When such information is written, a table showing the correspondence between the logical sector area and the physical sector area 60 is created based on this information.

  For example, FIGS. 6A to 6D show sector management information # 0 ′ to # 3 ′, which are modifications of the sector management information # 0 to # 3, respectively. In the sector management information # 0 ′ to # 3 ′, the set of the nth SLSN, SPSN, and SCNT corresponds to the nth series of data. As for a portion where data is written in the order of LSN from the first physical sector region 60 in the physical block, a portion corresponding to a plurality of series of data may be collected as one piece of information. For example, the portions corresponding to the first to fourth series of data may be combined into one piece of information such as SLSN # 16, SPSN # 0, and SCNT 96.

  In this modification, a table indicating the latest correspondence relationship between the logical sector area and the physical sector area 60 is created based on the latest sector management information. In this creation process, priority is given to the correspondence relationship between the logical sector area corresponding to a series of data written later and the physical sector area 60, and it corresponds to 256 logical sector numbers LSN # 0 to # 255. The physical sector number (PSN) is written in the recorded record. In other words, the physical sector number (PSN) written in each record may be overwritten with the physical sector number (PSN) corresponding to a series of data written later. The correspondence relationship between the logical sector area and the physical sector area 60 is grasped based on a set of SLSN, SPSN, and SCNT.

  For example, a table as shown in FIG. 5D is created based on the sector management information # 3 ′. In this table creation process, a physical sector number (PSN) is written in each record based on the correspondence between the logical sector area and the physical sector area 60 corresponding to each series of data. The writing of the physical sector number (PSN) is performed in order from the one corresponding to the previously written series of data. Even if the physical sector number (PSN) has already been written in the write destination record, The physical sector number (PSN) is overwritten. Accordingly, a table is created in which the correspondence between the logical sector area and the physical sector area 60 corresponding to a series of data written later is prioritized.

  <Second Embodiment>

  Hereinafter, a second embodiment of the present invention will be described. In that case, the difference from the first embodiment will be mainly described, and the description of the common points with the first embodiment will be omitted or simplified.

  In the second embodiment, logical sector areas in a logical block, which are grouped in units of sectors equal to the capacity of the user area 25 included in one physical page 60 in order from the top, are treated as logical pages, The correspondence relationship between the logical page included in the logical block and the physical page included in the physical block is managed in units of sectors equal to the capacity of the user area 25 included in one physical page. In the following description, a serial number assigned to a physical page in each physical block is referred to as a physical page number (PPN). A serial number assigned to a logical page in each logical block is called a logical page number (LPN). When a group is formed by collecting a plurality of physical blocks and one logical block is allocated to this group, one logical page is allocated to a plurality of physical pages. May be. In this case, the capacity of the logical page is equal to the capacity of the user area 25 included in a plurality of physical pages.

  In the present embodiment, one physical page is configured by the user area 25 of 4 sectors (2048 bytes) (4 physical sector areas 60 are included in one physical page), and 64 physical blocks are included. NAND type flash memory composed of physical pages is used. As shown in FIG. 2, with respect to the four physical sector areas 60 included in each physical page, the first physical sector area 60a, the second physical sector area 60a, and the second physical sector area 60a are arranged in order from the top (in order from the smallest column address). They are referred to as a physical sector area 60b, a third physical sector area 60c, and a fourth physical sector area 60d. Here, the first physical sector area 60a included in the physical page of PPN # 0 corresponds to the physical sector area of PSN # 0, and the second physical sector area 60b included in the physical page of PPN # 0 is PSN # 1. Corresponding to the physical sector area, the third physical sector area 60c included in the physical page of PPN # 0 corresponds to the physical sector area of PSN # 2, and the fourth physical sector area 60d included in the physical page of PPN # 0 is included. This corresponds to the physical sector area of PSN # 3. The first physical sector area 60a, the second physical sector area 60b, the third physical sector area 60c, and the fourth physical sector area 60d included in the physical page of the PPN # 1 include the physical sector areas of PSN # 4- # 7. The first physical sector area 60a, the second physical sector area 60b, the third physical sector area 60c, and the fourth physical sector area 60d included in the physical page of the PPN # 63 have the same corresponding relationship. The physical sector areas of PSN # 252- # 255 correspond to each other.

  Each logical page includes four logical sector areas. The LPN # 0 logical page includes LSN # 0- # 3 logical sector areas, the LPN # 1 logical page includes LSN # 4- # 7 logical sector areas, and so on. The allocated logical page of LPN # 63 includes the logical sector area of LSN # 252- # 255. The four logical sector areas included in each logical page are divided into four physical sector areas (first physical sector area 60a, second physical sector area 60b, third physical sector area 60c, and fourth physical area included in each physical page. The physical sector area 60d) is assigned in order from the smallest LSN.

  In the second embodiment, the correspondence relationship between the logical page and the physical page changes, but the relative relationship between the four physical sector areas 60 in the physical page and the four logical sector areas in the logical page changes. do not do. Therefore, in the second embodiment, by managing the correspondence between logical pages and physical pages, 256 logical sector areas included in the logical block and 256 physical sector areas 60 included in the physical block are Correspondence can be managed. That is, as in the present embodiment, if four physical sector areas 60 are included in one physical page, the physical sector area so that the lower 2 bits of the PSN and the lower 2 bits of the LSN always match. Correspondence between 60 and the logical sector area is defined. That is, the data corresponding to the LSN whose lower 2 bits are 00 is stored in the first physical sector 60a, the data corresponding to the LSN whose lower 2 bits are 01 is stored in the second physical sector 60b, and the lower 2 bits are 10 The data corresponding to the LSN is stored in the third physical sector, and the data corresponding to the LSN having the lower 2 bits of 11 is stored in the fourth physical sector. The logical page number (LPN) corresponds to the upper 6 bits of the 8-bit LSN, and the physical page number corresponds to the upper 6 bits of the 8-bit PSN.

  Hereinafter, an outline of writing in this embodiment will be described.

  The memory controller 3 writes a series of data given together with the write instruction to the flash memory 2 in accordance with a write instruction (write command and write destination address) given from the host system 4. In this writing process, the logical block to which the logical page to be written belongs is specified, and a series of data is written to the physical block corresponding to the logical block (or a physical block newly assigned to the logical block). . A series of data is written to the physical pages in the physical block in order from the top (that is, in order from the smallest PPN). Therefore, when the memory controller 3 writes a series of data, the end of the physical page in which the data in the physical block is written is searched. Then, a series of data is sequentially written from the physical page next to the last physical page. In other words, a series of data is sequentially written from the first physical page in which data in the physical block is not written.

  In the present embodiment, information indicating the correspondence between a logical page and a physical page (hereinafter referred to as “page management information”), such as logical A table indicating the correspondence between pages and physical pages is written. That is, the page management information is written in the user area 25 of the physical page, like the series of data given from the host system 4 together with the write instruction. Therefore, the memory controller 3 can grasp the correspondence between the logical page and the physical page by searching the end of the physical page in which data in the physical block is written and reading the page management information from the physical page. it can. The page management information in this embodiment is, for example, a table having 64 records respectively corresponding to the logical page numbers of 64 logical pages (see, for example, FIG. 8A described later).

  In the present embodiment, when writing a series of data, in order to determine whether or not to write page management information to a physical page in a physical block to which the series of data is written, a logic corresponding to the head data of the series of data is determined. A page (hereinafter referred to as “first logical page”) corresponds to a logical page (hereinafter, referred to as data stored in the last physical page in which data in a physical block in which the series of data is written is written. It is determined whether or not it is an area subsequent to “second logical page”. If it is determined by this determination that the first logical page is an area following the second logical page, the page management information is not written. On the other hand, if it is determined that the first logical page is not an area following the second logical page, page management information is written. That is, if the LPN of the first logical page is the next number of the LPN of the second logical page, the page management information is not written. On the other hand, if the LPN of the first logical page is not the next number of the LPN of the second logical page, page management information is written. If the data stored in the last physical sector area 60 where the data in the physical block is written is the page management information, the page management information is written without making the above determination.

  Therefore, in the case of a physical block in which no page management information is written, the first physical page is compared with a plurality of physical pages from the first physical page in the physical block to the last physical page in which data is written. Logical pages subsequent to the logical page corresponding to the data stored in are assigned in the order of LPN (hereinafter, such a state is referred to as “a state in which logical pages having continuous LPNs are assigned”). .

  For example, the last physical page in which the data in the physical block is written is the physical page of PPN # 42, the physical page of PPN # 0 to # 42 in the physical block is the logical page of LPN # 8 to # 50 When the corresponding data is written in the LPN order, the page management information is not written in the physical block.

  In the actual writing process, the following two determinations are made when writing a series of data.

  First, whether the data stored in the last physical page where the data in the physical block of the write destination is written is data written as a series of data or data written as page management information Is made. Here, if the data stored in the last physical page is page management information, the state where “a logical page with continuous LPNs is already allocated” has not been maintained, so the next determination is made. I will not.

  Next, if the data stored in the last physical page is not page management information, the data written to the physical page next to the last physical page (the first data of a series of data written in the current writing process) It is determined whether the LPN of the corresponding logical page is the next number of the LPN of the logical page corresponding to the data stored in the last physical page. If the data stored in the last physical page is not page management information, the already written data is in a state in which a logical page with continuous LPNs is allocated. When writing a series of data, it becomes a problem whether or not the state can be maintained. Here, the LPN of the logical page corresponding to the first data of the series of data written in the current writing process is the next to the LPN of the logical page corresponding to the data stored in the last physical page in which the data is written. If it is a number, even after writing this series of data, the “state where logical pages with continuous LPNs are allocated” is maintained. Therefore, the LPN of the logical page corresponding to the first data of the series of data written in the current writing process is the next number of the LPN of the logical page corresponding to the data stored in the last physical page in which the data is written. If so, the page management information is not written.

  In this embodiment, in order to determine the LPN of the logical page corresponding to the data stored in the physical page, as shown in FIG. 7, the common redundancy corresponding to the physical page in which the first data of a series of data is written. The LPN of the logical page corresponding to the head data is written in the area 50. Therefore, at least the LPN of the logical page corresponding to the data stored in the first physical page in the physical block is written in the common redundant area 50 corresponding to the first physical page.

  When the above determination is made, the last page where data is written is based on the LPN of the logical page corresponding to the data written to the first physical page and the PPN of the last physical page where data is written. The LPN of the logical page corresponding to the data stored in the physical page is obtained. Specifically, for example, data is written by adding the PPN value of the last physical page where data is written to the LPN value of the logical page corresponding to the data written to the first physical page. The LPN of the logical page corresponding to the data stored in the last physical page is obtained. Note that the LPN of the logical page corresponding to the data stored in the physical page may be written in the common redundant area 50 corresponding to the physical page in which the end data of the series of data is written by the memory controller 3.

  In the present embodiment, in order to detect a case where the writing process is terminated in the middle of writing due to a power shutdown or the like, the writing process is normally performed in the common redundant area 50 corresponding to the physical page in which the end data of the series of data is written. An end mark which is information indicating the end is written. However, when page management information is written, it corresponds to the common redundant area 50 corresponding to the physical page in which the page management information is written, that is, the physical page next to the physical page in which the end data of a series of data is written. An end mark is written in the common redundant area 50. By doing so, the memory controller 3 writes the page management information after the series of data has been written and the writing process is finished before the page management information is written due to power interruption or the like. Misunderstanding that this is the case can be avoided.

  Note that if the “state where logical pages with consecutive LPNs are allocated” is not maintained, the data stored in the last physical page in which the data in the physical block is written is the logical page and the physical page. It must be the latest page management information regarding the correspondence relationship. Therefore, when a series of data is written to a physical block that does not maintain the “state where logical pages with continuous LPNs are allocated”, the page management information is updated. The updated page management information is written in the physical page next to the physical page in which the tail data of the series of data is written. In updating the page management information, the contents of the page management information are updated for a portion corresponding to a series of data to be written. In this embodiment, page management information is written in order to make it possible to determine whether or not the data stored in the last physical page in which data in the physical block is written is page management information. A flag (hereinafter referred to as “management flag”) indicating that page management information has been written is written in the common redundant area 50 corresponding to the physical page. Thus, the memory controller 3 stores the management flag in the last physical page depending on whether or not the management flag is stored in the common redundant area 50 corresponding to the last physical page in which data in the physical block is written. It can be determined whether the stored data is page management information.

  In addition, when a plurality of series of data is continuously written in the same physical block, the page management information is not read from the last physical page in which the data in the physical block is written, and is held in the work area 8 The page management information being used may be used as it is.

  When the capacity of the data given from the host system 4 together with the write instruction is larger than the capacity of the empty page in the write destination physical block (first physical block), the memory controller 3 determines the end of the physical block. Data given from the host system 4 is written up to the physical page one page before the physical page, and page management information indicating the correspondence between the logical page and the physical page at that time is written to the last physical page. The remaining data is written to a physical page in another newly allocated physical block (second physical block). That is, when all the data corresponding to each logical page in the logical block is written in the order of LPN from the first physical page of the first physical block to the last physical page (data corresponding to the first logical page) Page management information is written to the last physical page (except when written in the order of LPN to LPN).

  When writing a series of data, if the empty page in the first physical block is only the last physical page, the series of data is not written to the last physical page, and the second physical page is not written. Writing of a series of data is started from the first physical page of the block.

  When reading the data stored in each physical page from the physical block, the memory controller 3 reads the page management information from the last physical page in which the data in the physical block is written, and based on this page management information Understand the correspondence between logical pages and physical pages.

  Hereinafter, a specific example of the writing process according to the present embodiment will be described with reference to FIGS. As described above, a series of data is written in order from the smallest PPN. In the following description, a series of data written in the nth (n is a natural number) is referred to as an “nth series of data”. Also, the logical page to be accessed (one or more logical pages from the logical page to which the logical sector area corresponding to the first data of a series of data belongs to the logical page to which the logical sector area corresponding to the last data of the series belongs) Page) is called "logical access page". In this specific example, as shown in FIG. 7A, a physical block of PBA # 7 is allocated to a logical block of LBN # 0.

  First, based on the first write instruction given from the host system 4, eight logical pages LPN # 8- # 15 in the logical block of LBN # 0 are specified as logical access pages. Further, since there is no physical block corresponding to the logical block of LBN # 0, the physical block of PBA # 7 is assigned to the logical block of LBN # 0. Since data is not yet written in this physical block, the first physical page in the physical block of PBA # 7 (physical page of PPN # 0) is the first physical page in which no data in the physical block is written. Is identified. The first series of data write processing corresponding to the first write instruction is started from the first physical page (physical page of PPN # 0). As a result, the first series of data corresponding to the eight logical pages of LPN # 8- # 15 is written to the eight physical pages of PPN # 0- # 7. Also, the LPN (LPN # 8- #) of the logical page corresponding to the head data is stored in the common redundant area 50 corresponding to the physical page (PPN # 0 physical page) in which the head data of the first series of data is written. The value “# 8” of the LPN of the first logical page among the 15 eight logical pages is written (see FIG. 7A).

  Since the first series of data is the first series of data written to the physical block, at the stage where the first series of data is written, “a state where logical pages with continuous LPNs are allocated” Is maintained. For this reason, the page management information is not written to the physical page next to the physical page (PPN # 7 physical page) in which the tail data of the first series of data is written, and the common redundancy corresponding to the physical page of PPN # 7. An end mark (EM (End Mark)) is written in the area 50.

  Next, based on the second write instruction given from the host system 4, eight logical pages LPN # 16- # 23 in the logical block of LBN # 0 are specified as logical access pages. Further, the physical page of PPN # 7 is specified as the last physical page in which data in the physical block of PBA # 7 corresponding to the logical block of LBN # 0 is written. The writing of the second series of data corresponding to the second write instruction is started from the physical page (physical page of PPN # 8) next to the identified last physical page (physical page of PPN # 7). The As a result, the second series of data corresponding to the eight logical pages of LPN # 16- # 23 is written to the eight physical pages of PPN # 8- # 15. Also, the LPN (LPN # 16− of the logical page corresponding to the head data is stored in the common redundant area 50 corresponding to the physical page (PPN # 8 physical page) in which the head data of the second series of data is written. The value “# 16” of the LPN of the first logical page among the eight logical pages of # 23 is written (see FIG. 7A).

When this writing process is started, it is determined whether or not the data stored in the last physical page (physical page of PPN # 7) in which data in the physical block is written is page management information. . Since the data stored in the physical page of PPN # 7 is not page management information, the LPN of the first logical page (the logical page corresponding to the first data of the second series of data) is the second logical page ( It is determined whether or not it is the number next to the LPN of the logical page corresponding to the data stored in the last physical page in which the data is written. Specifically, the PPN value “# 7” of the last physical page in which data is written is added to the LPN value “# 8” written in the common redundant area 50 corresponding to the first physical page. The value “# 15” is obtained as the LPN of the second logical page. Meanwhile, LPN of the first logical page
Since “# 16”, the LPN of the first logical page is determined to be the next number of the LPN of the second logical page. In this way, when the LPN of the first logical page is the next number of the LPN of the second logical page, even after a series of data is written, the “state where logical pages with continuous LPNs are allocated” remains. Maintained.

  In this writing process, the “state in which logical pages with continuous LPNs are allocated” is maintained, so that the physical page (the physical page of PPN # 15) where the tail data of the second series of data is written is next. The page management information is not written in the physical page, and the end mark is written in the common redundant area 50 corresponding to the physical page of PPN # 15.

  As shown in FIG. 7A, the second series of data and the fourth series of data respectively corresponding to the third write instruction and the fourth write instruction given from the host system 4 are also the second A writing process similar to a series of data is executed.

  Next, eight logical pages LPN # 0- # 7 in the logical block of LBN # 0 are specified as logical access pages based on the fifth write instruction given from the host system 4. Also, the physical page of PPN # 47 is specified as the last physical page in which data in the physical block of PBA # 7 corresponding to the logical block of LBN # 0 is written. Writing of the fifth series of data corresponding to the fifth write instruction is started from the physical page (physical page of PPN # 48) next to the identified last physical page (physical page of PPN # 47). . As a result, the fifth series of data corresponding to the eight logical pages of LPN # 0 to # 7 is written to the eight physical pages of PPN # 48 to # 55. Further, the LPN (LPN # 0- #) of the logical page corresponding to the head data is stored in the common redundant area 50 corresponding to the physical page (physical page of PPN # 48) in which the head data of the fifth series of data is written. 7 is written, the value “# 0” of the first logical page among the eight logical pages (see FIG. 7A).

When this writing process is started, it is determined whether or not the data stored in the last physical page in which data in the physical block is written (physical page of PPN # 47) is page management information. . Since the data stored in the physical page of PPN # 47 is not page management information, the LPN of the first logical page (the logical page corresponding to the first data of the fifth series of data) is the second logical page ( It is determined whether or not it is the number next to the LPN of the logical page corresponding to the data stored in the last physical page in which the data is written. Specifically, “# 8” is the value obtained by adding the PPN value “# 47” of the last physical page to the LPN value “# 8” written in the common redundant area 50 corresponding to the first physical page. 55 ″ is determined as the LPN of the second logical page. Meanwhile, LPN of the first logical page
Is “# 0, it is determined that the LPN of the first logical page is not the next number of the LPN of the second logical page. In this way, the LPN of the first logical page is the LPN of the second logical page. If it is not the next number, after writing a series of data, the “state where logical pages with continuous LPNs are allocated” is not maintained.

  In this writing process, the “state where logical pages with consecutive LPNs are allocated” is not maintained, so that the memory controller 3 stores the valid data stored in the physical block when the fifth series of data has been written. Page management information # 0 indicating the correspondence between the physical page (PPN # 0- # 55 physical page) related to the correct data and the logical page is created. Here, since the data stored in the last physical page (the physical page of PPN # 47) in which the data before the fifth series of data is written is not page management information (the physical page of PPN # 47) Since the management flag is not written in the common redundant area 50 corresponding to the above, the page management information is newly created. Specifically, a table creation area having 64 records respectively corresponding to LPN # 0 to # 63 is secured on the work area 8, and PPN is written in each record of this table creation area. When creating the page management information # 0 as shown in FIG. 8A, first, LPN # 8- written to the physical pages of PPN # 0- # 47 as a series of first to fourth data. PPN writing relating to data corresponding to the logical page # 55 is performed. That is, the numbers (PPN values) of PPN # 0- # 47 are written in the records corresponding to LPN # 8- # 55. Next, the PPN is written for the data corresponding to the logical pages LPN # 0- # 7 written to the physical pages PPN # 48- # 54 as the fifth series of data. That is, the numbers (PPN values) of PPN # 48- # 54 are written in the records corresponding to LPN # 0- # 7. Thereby, the creation processing of the page management information # 0 as shown in FIG.

  The memory controller 3 uses the created page management information # 0 as the physical page (physical page of PPN # 56) next to the physical page (physical page of PPN # 55) in which the tail data of the fifth series of data is written. Write to. In addition, a management flag (not shown) and the above-described end mark are written in the common redundant area 50 corresponding to the physical page in which page management information # 0 is written (physical page of PPN # 56) (FIG. 7A). reference).

  For a physical block in which page management information has been written even once, page management information is written each time a series of data is written to the physical block. This is because the physical block in which the page management information has been written even once does not maintain the “state in which logical pages with continuous LPNs are allocated”.

  Next, based on the sixth write instruction given from the host system 4, eight logical pages LPN # 8- # 15 in the logical block of LBN # 0 are specified as logical access pages. Also, the physical page of PPN # 56 is specified as the last physical page in which data in the physical block of PBA # 7 corresponding to the logical block of LBN # 0 is written.

  However, since the free pages in the physical block of PBA # 7 are only seven physical pages of PPN # 57- # 63, the memory controller 3 performs the eight pages based on the sixth write instruction given from the host system 4. All data corresponding to the logical page cannot be written to an empty page in the physical block of PBA # 7.

  Further, since the data stored in the last physical page (PSN # 56 physical page) in which the data in the physical block is written is the page management information, “a logical page with continuous LPN has already been allocated. "State" is not maintained. Therefore, the memory controller 3 must write page management information to the last physical page in the physical block.

  Therefore, the data corresponding to the eight logical pages based on the sixth write instruction includes the sixth series of data including the data corresponding to the six logical pages and the data corresponding to the two logical pages. Divided into a seventh series of data.

  First, a sixth series of data write processing will be described. The sixth series of data starts from the physical page (PSN # 56 physical page) next to the last physical page (PSN # 56 physical page) in which data in the physical block of PBA # 7 is written. The data is written in six physical pages up to the physical page (physical page of PPN # 62) one page before the tail physical page (physical page of PPN # 63). Page management indicating the correspondence between the logical page and the physical page at the time when writing of the sixth series of data is completed in the last physical page (physical page of PPN # 63) in the physical block of PBA # 7 Information # 1 is written. In addition, a management flag (not shown) and the above-described end mark are written in the common redundant area 50 corresponding to the last physical page (PPN # 63 physical page) in which the page management information # 1 is written.

  Next, a seventh series of data writing processing will be described. As shown in FIG. 7B, another physical block (physical block of PBA # 16) is newly allocated to the logical block of LBN # 0, and the first physical page (PPN) in the physical block of PBA # 16 is allocated. The seventh series of data is written from the physical page # 0. In addition, the end mark is written in the common redundant area 50 corresponding to the physical page (PPN # 1 physical page) in which the end data of the seventh series of data is written.

  As a result, among the data corresponding to the eight logical pages given from the host system 4, the data corresponding to the sixth logical page from the head is PPN # 57- # in the physical block of PBA # 7. 62 is written as a sixth series of data (see FIG. 7A), and the data corresponding to the remaining two logical pages are PPN # 0- # 1 in the physical block of PBA # 16. Are written as a seventh series of data in the physical page (see FIG. 7B).

  If the memory controller 3 cannot write all the data given together with the write instruction from the host system 4 to the empty page in the physical block of PBA # 7 as described above, the memory controller 3 newly allocates all the data. Alternatively, it may be written in the physical block of PBA # 16.

  In addition, when the number of write destination logical pages specified by the write instruction given from the host system 4 is equal to or greater than the number of physical pages in which data in the write destination physical block is not written, the last page in the physical block In this physical page, page management information is written instead of data given from the host system 4. If the data stored in the last physical page is not page management information, the data corresponding to each logical page in the logical block from the first physical page to the last physical page in the physical block is all in the LPN order. This is because it is determined that data is written (written in the order of LPN from the data corresponding to the first logical page).

  Therefore, even if the data (a series of data) given from the host system 4 is written up to the last physical page in the physical block, the “state where logical pages with continuous LPNs are allocated” is maintained. Not the page management information but data (a series of data) given from the host system 4 is written to the last physical page.

  When two physical blocks are assigned to one logical block, page management information including the first physical block and the second physical block is stored in the second physical block. It is preferable that However, the page management information does not have to be stored in the second physical block as long as “a state in which logical pages with continuous LPNs are allocated” is maintained in the second physical block. . If page management information is not stored in the second physical block, a page combining the first physical block and the second physical block based on the page management information related to the first physical block Management information is created.

  The above-described page management information # 1 is created as follows.

  That is, because page management information # 0 is written to the last physical page (physical page of PPN # 56) in which data before the sixth series of data is written (data is written). If the page management information # 0 is not held in the work area 8, the page management is started from the physical page of PPN # 56. Information # 0 is read out. The page management information # 1 is created based on the read page management information # 0. In this creation process, as shown in FIG. 8B, in the six physical pages 60 in which the sixth series of data is written in the record corresponding to LPN # 8- # 13 in the page management information # 0. The corresponding PPN # 57- # 62 is overwritten.

  As described above, the seventh series of data, which is data for two pages, is written in the physical block of PBA # 16, but the first series of data is written in the physical block of PBA # 16 for the first time. Therefore, it is determined that the page management information is not written in the physical page next to the physical page (the physical page of PPN # 1) in which the tail data of the seventh series of data is written, and the physical page of PPN # 1 is determined. An end mark is written in the corresponding common redundant area 50.

  Next, based on the seventh write instruction given from the host system 4, eight logical pages LPN # 16- # 23 in the logical block of LBN # 0 are specified as logical access pages. Further, the physical page of PPN # 1 is specified as the last physical page in which data in the physical block of PBA # 16 corresponding to the logical block of LBN # 0 is written. The eighth series of data write processing corresponding to the seventh write instruction is started from the physical page (PPN # 2 physical page) next to the identified last physical page (PPN # 1 physical page). The As a result, the eighth series of data corresponding to the eight logical pages of LPN # 16- # 23 is written to the eight physical pages of PPN # 2- # 9. Also, the LPN (LPN # 16- #) of the logical page corresponding to the head data is stored in the common redundant area 50 corresponding to the physical page (the physical page of PPN # 2) in which the head data of the eighth series of data is written. 23, the value “# 16” of the LPN of the first logical page among the eight logical pages is written (see FIG. 7B).

  When this writing process is started, it is determined whether or not the data stored in the last physical page (physical page of PPN # 1) in which data in the physical block is written is page management information. . Since the data stored in the physical page of PPN # 1 is not page management information, the LPN of the first logical page (the logical page corresponding to the first data of the eighth series of data) is the second logical page ( It is determined whether or not it is the number next to the LPN of the logical page corresponding to the data stored in the last physical page in which the data is written. Here, since the LPN value of the first logical page is “# 16” and the LPN value of the second logical page is “# 15”, the LPN of the first logical page is the second logical page. It is determined that it is the next number of the LPN of the page. Therefore, the page management information is not written to the physical page next to the physical page (PPN # 9 physical page) in which the tail data of the eighth series of data is written, and the common redundancy corresponding to the physical page of PPN # 9 is used. An end mark is written in area 50.

  Next, eight logical pages LPN # 0 to # 7 in the logical block of LBN # 0 are specified as logical access pages based on the eighth write instruction given from the host system 4. Also, the physical page of PPN # 9 is specified as the last physical page in which data in the physical block of PBA # 16 corresponding to the logical block of LBN # 0 is written. Writing of the ninth series of data corresponding to the eighth write instruction is started from the physical page (physical page of PPN # 10) next to the identified last physical page (physical page of PPN # 9). . Here, as shown in FIG. 7B, the ninth series of data corresponding to the eight logical pages of LPN # 0 to # 7 is transferred to the eight physical pages of PPN # 10 to # 17. Written. In addition, in the common redundant area 50 corresponding to the physical page (PPN # 10 physical page) in which the top data of the ninth series of data is written, the LPN (LPN # 0−) of the logical page corresponding to the top data is stored. The value “# 0” of the LPN of the first logical page among the eight logical pages of # 7 is written (see FIG. 7B).

  When starting the writing process, it is determined whether or not the data stored in the last physical page (physical page of PPN # 9) in which the data in the physical block is written is page management information. . Since the data stored in the physical page of PPN # 9 is not page management information, the LPN of the first logical page (the logical page corresponding to the head data of the ninth series of data) is the second logical page ( It is determined whether or not it is the number next to the LPN of the logical page corresponding to the data stored in the last physical page in which the data is written. Here, since the LPN value of the first logical page is “# 0” and the LPN value of the second logical page is “# 23”, the LPN of the first logical page is the second logical page. It is determined that it is not the next number of the LPN of the page.

  Therefore, in the ninth series of data write processing, the “state where logical pages with continuous LPNs are allocated” is not maintained, so the memory controller 3 creates page management information # 2. The physical block of PBA # 16 is the second physical block corresponding to the logical block of LBN # 0. Therefore, the memory controller 3 creates page management information # 2 based on the page management information # 1 written in the last physical page of the first physical block.

  A process for creating the page management information # 2 created when the ninth series of data is written will be described with reference to FIG. Since the PPN described in each record of the page management information # 1 which is the basis of the page management information # 2 is a PPN corresponding to the physical block in the first physical block, each PPN is written. An old block flag (described as “old block F” in the figure), which is information indicating the first physical block, is written in the record. Next, the contents of the page management information # 1 are updated with respect to the data corresponding to the logical pages LPN # 14- # 23 written to the physical pages PPN # 0- # 9 as the seventh and eighth series of data. The That is, the record corresponding to LPN # 14- # 23 is overwritten with the number of PPN # 0- # 9 (PPN value), and the old block flag described in the record with the number (PPN value) overwritten. Is erased. Next, the contents of the page management information # 1 are updated for the data corresponding to the logical pages of LPN # 0 to # 7 written to the physical pages of PPN # 10 to # 17 as the ninth series of data. That is, the record corresponding to LPN # 0- # 7 is overwritten with the number (PPN value) of PPN # 10- # 17, and the old block flag described in the record with the number (PPN value) overwritten. Is erased.

  The old block flag indicates that the PPN written in each record is the PPN of the physical page in the first physical block (in this specific example, the physical block of PBA # 7), or the second physical block This is information for determining whether it is a PPN of a physical page in (physical block of PBA # 16 in this specific example). That is, the PPN written in the record in which the old block flag is written is determined to be the PPN of the physical page in the first physical block (physical block of PBA # 7 in this specific example). That is, by referring to the page management information # 2, the data corresponding to the logical pages of LPN # 0- # 7 and LPN # 14- # 23 is stored in the second physical block (in this specific example, PBA # 16 It can be seen that data corresponding to another logical page is written in the second physical block. The page management information # 2 created as described above is the next to the physical page (the physical page of PPN # 17 in the second physical block) in which the end data of the ninth series of data is written. Physical page (physical page of PPN # 18 in the second physical block) and physical page written with page management information # 2 (physical page of PPN # 18 in the second physical block) A management flag (not shown) and the end mark described above are written in the common redundant area 50 corresponding to.

  In this specific example, the physical block of PBA # 7 (first physical block) and the physical block of PBA # 16 (second physical block) are the same logical block (logical block of LBN # 0). Correspondence can be determined by referring to the logical address information written in these physical blocks. In addition, in order to determine the new / old relationship of these physical blocks (determine the first physical block or the second physical block), the memory controller 3 sets the new / old relationship in the common redundant area 50 corresponding to the first physical page. It is preferable to write a serial number to determine the above. In addition, the memory controller 3 in the common redundant area 50 corresponding to the first physical page of the new block (second physical block) or the common redundant area 50 corresponding to the physical page in which the page management information is written is stored in the old block. The PBA of (first physical block) may be written. In this way, the PBA of the old block (first physical block) can be grasped by referring to those common redundant areas 50.

  After that, when data is read from the first physical block or the second physical block assigned to the same logical block, the memory controller 3 is written with data in the second physical block. The page management information # 2 is read from the last physical page (PPN # 18 physical page), and the correspondence between the logical page and the physical page is grasped based on the page management information # 2. Here, since the page management information # 2 written in the physical page of the PPN # 18 in the new block indicates the latest correspondence between the logical page and the physical page, the page management information # 2 is referred to. Only the latest correspondence relationship between the logical page and the physical page can be grasped. Specifically, the data corresponding to the logical pages of LPN # 0- # 7 and LPN # 14- # 23 is written in the second physical block, and the data corresponding to the other logical pages is 1 It is understood that data is written in the physical block. That is, according to the present embodiment, it is possible to efficiently grasp the correspondence between the logical page and the physical page.

  When data is read from a physical block between the time when the first series of data is written and before the time when the fifth series of data is written (that is, when no page management information is written), When the memory controller 3 writes the data corresponding to the logical pages after the logical page (LPN # 8 logical page) corresponding to the data stored in the first physical page in the physical block in the LPN order. Judgment is made to grasp the correspondence between the logical page and the physical page. Further, the LSN of the logical page corresponding to the data stored in the first physical page in the physical block is grasped by the LSN written in the common redundant area 50 corresponding to the first physical page.

  In addition, the page management information is written in the first physical block after the seventh series of data is written and before the ninth series of data is written. When data is not read from the physical block (first physical block or second physical block) when no page management information is written in the physical block, the memory controller 3 reads the first physical block. Is created based on the page management information written in the first physical block and the second physical block. In this creation process, the content of the page management information written in the first physical block is updated for the portion corresponding to the data stored in the second block. At this time, regarding the second block block, it is determined that the data is stored in the order of LPN from the data corresponding to the logical page of LPN 14, and the correspondence between the logical page and the physical page is grasped.

  The above is the description of the second embodiment.

  The page management information is preferably a table indicating the correspondence between logical pages and physical pages as described above, but as a modification, the top data of each series of data written in the physical block And a start logical page number (hereinafter referred to as “SLPN”) that is a logical page number of the logical page corresponding to, and a start physical page number (hereinafter referred to as “SLPN”). SPPN ”) and the number of pages to which the series of data is written (a page count value that is the number of logical pages from the logical page to which the first data belongs to the logical page to which the last data belongs, hereinafter referred to as“ PCNT ”) And information indicating a physical block in which the series of data is written (first physical block or second physical block) Physical block may be information) indicating. When such information is written, a table indicating the correspondence between logical pages and physical pages is created based on this information.

  For example, FIGS. 10A to 10C show page management information # 0 ′ to # 2 ′, which are modified examples of the page management information # 0 to # 2. In the page management information # 0 ′ to # 2 ′, the nth SLPN, SPPN, and PCNT set corresponds to the nth series of data. In the page management information # 2 ′ written in the second physical block, the old block flag is included in the set of SLPN, SPPN and PCNT corresponding to a series of data written in the second physical block. Are associated. As for a portion where data is written in the order of LPN from the first physical page in the physical block, portions corresponding to a plurality of series of data may be collected as one piece of information. For example, portions corresponding to the first to fourth series of data may be combined into one piece of information such as # 8 for SLPN, # 0 for SPPN, and 48 for PCNT.

  In this modification, a table indicating the latest correspondence between logical pages and physical pages is created based on the latest page management information. In this creation process, the correspondence between logical pages and physical pages corresponding to a series of data written later is prioritized, and 64 logical page numbers (LPN) LPN # 0 to # 63 are supported. The physical page number (PPN) is written in the recorded record. That is, the physical page number (PPN) written in each record may be overwritten with the physical page number (PPN) corresponding to a series of data written later. The correspondence relationship between the logical page and the physical page is grasped based on the set of SLPN, SPPN, and PCNT.

  For example, a table as shown in FIG. 9 is created based on the page management information # 2 ′. In this table creation process, a physical page number (PPN) is written in each record based on the correspondence between the logical page and physical page corresponding to each series of data. The writing of the physical page number (PPN) is performed in order from the one corresponding to the previously written series of data. Even if the physical page number (PPN) is already written in the write destination record, the physical page number (PPN) is written later. The physical page number (PPN) is overwritten. Therefore, a table is created that prioritizes the correspondence between logical pages and physical pages corresponding to a series of data written later.

  As mentioned above, although several embodiment of this invention was described, these are the illustrations for description of this invention, Comprising: It is not the meaning which limits the scope of the present invention only to these embodiment. Of course, various modifications can be made without departing from the scope of the present invention.

  For example, in the above embodiment, the number of physical sector areas included in the logical block area and the physical block included in the logical block is the same. However, the number of logical sector areas included in the logical block may be smaller than the number of physical sector areas included in the physical block. In this way, even after data corresponding to all logical sector areas included in the logical block is stored in the physical block, the rewrite data of the data is changed to the empty area (data is written in the physical block). Not stored in a physical sector area or physical page). This makes it possible to efficiently rewrite data. For example, when the number of logical sector areas included in the logical block and the number of physical sector areas included in the physical block are both given by powers of 2, the number of logical sector areas included in the logical block Is 128, and the number of physical sector areas included in the physical block is 256.

  In the above embodiment, the end mark indicating that the writing process has been normally completed is written in the divided redundant area 70 or the common redundant area 50. However, the management flag, logical sector number, or logical page number It may be made to serve as an end mark.

  That is, only when the sector management information (or page management information) is not written, the divided redundant area 70 (or common redundant area) corresponding to the physical sector area 60 (or physical page) in which the end data of the series of data is written. 50), the logical sector number (or logical page number) of the logical sector area (or logical page) corresponding to the tail data may be written. When the sector management information (or page management information) is written, the divided redundant area 70 (or common redundant area 50) corresponding to the physical sector area 60 (or physical page) in which the end data of a series of data is written is written. The logical sector number (or logical page number) is not written and the divided redundant area 70 (or common redundant area 50) corresponding to the physical sector area 60 (or physical page) in which the sector management information (or page management information) is written is written. Management flag is written. In this way, the management flag or the logical sector number (or logical page number) is written into the divided redundant area 70 (or the common redundant area 50) only when the writing process is normally completed. Further, when sector management information (or page management information) is not written, a logical sector area (or corresponding to data stored in the last physical sector area 60 (or physical page) in which data is written). The logical sector number (or logical page number) of the logical page is stored in the divided redundant area 70 (or common redundant area 50) corresponding to the last physical sector area 60 (or physical page) in which data is written. Therefore, the logical sector number of the second logical sector area can be easily obtained. In this case, the divided redundant area 70 (or common redundant area 50) corresponding to the physical sector area 60 (or physical page) in which the first data of a series of data is written corresponds to the first data. Since it is not necessary to write the logical sector number (or logical page number) of the logical sector area (or logical page) to be executed, the logical sector number (or logical page number) of the logical sector area (or logical page) corresponding to the head data is eliminated. ) Is not written.

1 is a block diagram showing a schematic configuration of a flash memory system according to a first embodiment of the present invention. It is a figure which shows the structure of the physical page of flash memory. It is a figure which shows the correspondence of a logical block and a physical block. FIG. 4A shows an example of a result of writing to the first half portion of 256 physical sector areas in the physical block. FIG. 4B shows an example of the result of writing to the latter half of the 256 physical sector areas in the physical block. FIG. 5A shows the contents of sector management information # 0 shown in FIG. FIG. 5B shows the contents of sector management information # 1 shown in FIG. FIG. 5C shows the contents of the sector management information # 2 shown in FIG. FIG. 5D shows the contents of the sector management information # 3 shown in FIG. FIG. 6A shows a modification of the sector management information # 0 shown in FIG. FIG. 6B shows a modification of the sector management information # 1 shown in FIG. FIG. 6C shows a modification of the sector management information # 2 shown in FIG. FIG. 6D shows a modification of the sector management information # 3 shown in FIG. FIG. 7A shows an example of a result of writing to one physical block PBA # 7 assigned to the same logical block. FIG. 7B shows an example of a result of writing to the other physical block PBA # 16 assigned to the same logical block. FIG. 8A shows the contents of the page management information # 0 shown in FIG. FIG. 8B shows the contents of the page management information # 1 shown in FIG. FIG. 9 shows the contents of the page management information # 2 shown in FIG. FIG. 10A shows a modification of the page management information # 0 shown in FIG. FIG. 10B shows a modification of the page management information # 1 shown in FIG. FIG. 10C shows a modification of the page management information # 2 shown in FIG.

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 including a plurality of physical sector areas, based on an access instruction given from a host system,
A block management means for managing a correspondence relationship between a logical block composed of a plurality of logical sector areas and the physical block;
Empty sector area search means for searching for the beginning of the physical sector area in which data in the physical block corresponding to the logical block to which the logical access area specified as the area to be accessed by the access instruction belongs is not written;
A series of data instructed to be written to the logical access area by the access instruction is transferred from the head physical sector area to which the data detected by the free sector area search means is not written, to the physical address at the end. Data writing means for sequentially writing toward the sector area;
The first area, which is the logical sector area corresponding to the head data of a series of data instructed to be written to the logical access area by the access instruction, corresponds to the logical block to which the logical access area belongs. Judgment means for judging whether it is an area following the second area which is the logical sector area corresponding to the data stored in the last physical sector area in which the data in the physical block is written When,
The physical sector area in the physical block in which the series of data has been written by the data writing means when the determining means determines that the first area is not an area following the second area And sector management information indicating a correspondence relationship with the logical sector area in the logical block corresponding to the physical block, the physical sector area next to the physical sector area in which the end data of the series of data is written Sector management information writing means for writing to
With
The determination means determines that the first area is not an area following the second area when the data stored in the physical sector area at the end is the sector management information.
A memory controller characterized by that. The determination means is a determination means for determining whether or not the first area is an area following the second area based on a serial number assigned to the logical sector area in the logical block. Determining that the first area is not an area following the second area when the serial number corresponding to the first area is not the next number of the serial number corresponding to the second area;
The memory controller according to claim 1. The data stored in the physical sector area in the physical block corresponding to the logical block to which the logical access area specified by the access instruction belongs is changed to the end of the data in which the data in the physical block is written. Further comprising data reading means for reading based on the sector management information stored in the physical sector area,
The memory controller according to claim 1, wherein the memory controller is a memory controller. When the sector management information is not stored in the physical block corresponding to the logical block to which the logical access area belongs, the data read means stores the data stored in the physical block in the physical block. The data corresponding to the logical sector area after the logical sector area corresponding to the data stored in the head physical sector area is regarded as being written in the order of the logical sector area, and data is read. ,
The memory controller according to claim 3. A memory controller that controls access to a flash memory that is erased in units of physical blocks including a plurality of physical pages, 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 logical pages and the physical block;
Empty page search means for searching for the top of the physical page in which data in the physical block corresponding to the logical block to which the logical access page designated as the logical page to be accessed belongs by the access instruction belongs,
A series of data instructed to be written to the logical access page by the access instruction is transferred from the first physical page to which the data detected by the empty page search unit is not written to the last physical page. Data writing means for sequentially writing toward the
The first page which is the logical page corresponding to the first data of a series of data instructed to be written to the logical access page by the access instruction corresponds to the logical block to which the logical access page belongs. Determining means for determining whether the page is subsequent to the second page that is the logical page corresponding to the data stored in the last physical page in which data in the physical block is written;
When the determining means determines that the first page is not a page following the second page, the physical page in the physical block in which the series of data has been written by the data writing means Page management information for writing page management information indicating a correspondence relationship with the logical page in the logical block corresponding to the physical block to the physical page next to the physical page in which the end data of the series of data is written Information writing means;
With
The determination unit determines that the first page is not a page following the second page when the data stored in the physical page at the end is the page management information;
A memory controller characterized by that. The determination means is a determination means for determining whether the first page is a page following the second page based on a serial number assigned to the logical page in the logical block, Determining that the first page is not a page following the second page when the serial number corresponding to the first page is not the next number of the serial number corresponding to the second page;
The memory controller according to claim 5. The data stored in the physical page in the physical block corresponding to the logical block to which the logical access page specified by the access instruction belongs is changed to the last physical in which the data in the physical block is written. Data reading means for reading based on the page management information stored in the page;
The memory controller according to claim 5, wherein the memory controller is a memory controller. When the page management information is not stored in the physical block corresponding to the logical block to which the logical access page belongs, the data read means stores the data stored in the physical block in the physical block. The data corresponding to the logical pages after the logical page corresponding to the data stored in the first physical page is regarded as being written in the order of the logical pages, and data is read.
The memory controller according to claim 7. A memory controller according to any one of claims 1 to 8,
And a flash memory system accessed by the memory controller. A flash memory control method in which erasure is performed in units of physical blocks including a plurality of physical sector areas based on an access instruction given from a host system,
A block management step for managing a correspondence relationship between a logical block composed of a plurality of logical sector areas and the physical block;
A free sector area search step for searching for the beginning of the physical sector area in which data in the physical block corresponding to the logical block to which the logical access area designated as the access target area by the access instruction belongs is not written;
A series of data instructed to be written to the logical access area by the access instruction is transferred from the first physical sector area to which the data detected by the free sector area search step is not written to the last physical sector. A data writing step of sequentially writing toward the sector area;
The first area, which is the logical sector area corresponding to the head data of a series of data instructed to be written to the logical access area by the access instruction, corresponds to the logical block to which the logical access area belongs. A determination step of determining whether or not it is an area following the second area which is the logical sector area corresponding to the data stored in the physical sector area at the end in which the data in the physical block is written When,
When the determination step determines that the first area is not an area following the second area, the physical sector area in the physical block in which the series of data has been written by the data write step And sector management information indicating a correspondence relationship with the logical sector area in the logical block corresponding to the physical block, the physical sector area next to the physical sector area in which the end data of the series of data is written Sector management information writing step to write to,
With
In the determination step, when the data stored in the physical sector area at the end is the sector management information, it is determined that the first area is not an area subsequent to the second area.
A method for controlling a flash memory. A flash memory control method in which erasure is performed in units of physical blocks including a plurality of physical pages based on an access instruction given from a host system,
A block management step for managing a correspondence relationship between a logical block composed of a plurality of logical pages and the physical block;
A free page search step of searching for the top of the physical page in which data in the physical block corresponding to the logical block to which the logical access page designated as the logical page to be accessed by the access instruction belongs is not written;
A series of data instructed to be written to the logical access page by the access instruction is transferred from the first physical page to which the data detected by the empty page search step is not written to the last physical page. A data writing step of sequentially writing toward the
The first page which is the logical page corresponding to the first data of a series of data instructed to be written to the logical access page by the access instruction corresponds to the logical block to which the logical access page belongs. A determination step of determining whether or not the page is subsequent to the second page which is the logical page corresponding to the data stored in the last physical page in which data in the physical block is written;
When the determination step determines that the first page is not a page subsequent to the second page, the physical page in the physical block in which the series of data has been written by the data writing step Page management information for writing page management information indicating a correspondence relationship with the logical page in the logical block corresponding to the physical block to the physical page next to the physical page in which the end data of the series of data is written An information writing step;
With
In the determination step, when the data stored in the physical page at the end is the page management information, it is determined that the first page is not a page subsequent to the second page.
A method for controlling a flash memory.

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