JP2008299455A - Data storage device and data management method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a data storage device and a data management method for improving a processing speed when reading data from a non-volatile semiconductor memory. <P>SOLUTION: Data corresponding to a plurality of types of data ID are written in each block 21 of the non-volatile semiconductor memory 1, and when data are written in each block 21, the data ID of data written in a page and information showing the position of a page in which the data corresponding to the other data ID have been finally written are stored in the redundancy area 24 of the finally written page of each block 21. Since host equipment can access desired data by instantaneously creating an ID/page map 61 based on information of the redundant area 24, it is possible to remarkably improve a processing speed when reading data. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a data storage device using a nonvolatile semiconductor memory as a storage medium and detachable from a host device, and a data management method in the data storage device.
About.

  Conventionally, NAND-type non-volatile semiconductor memory (flash memory) has been used as the main storage medium. For example, it is portable and detachable from a host device such as a PC (Personal Computer), a mobile phone, or a portable AV (Audio / Video) device. Data storage devices (so-called memory cards) are known. In this memory card, for example, data writing and reading are managed by a file management system on the host device side such as a FAT (File Allocation Tables) file system. In the memory card, the physical area in the non-volatile semiconductor memory is divided into a plurality of blocks, which are used as data erasure units. The block is further divided into a plurality of pages, and the page is a unit for writing and reading data.

  When writing, reading and erasing data using the file management system, the logical address given from the system side of the host device and the physical address of the page in the nonvolatile semiconductor memory uniquely correspond to each other. Therefore, it is necessary to manage the correspondence within the memory card. As one of the management methods, there is a method in which a correspondence relationship between a logical address and a physical address is recorded on a nonvolatile semiconductor memory inside a memory card and updated whenever the correspondence relationship changes. However, this method has a drawback that the processing speed of the entire system is reduced, and that it is difficult to recover when management information is lost due to power-off during processing.

Therefore, as a method for making up for the above drawbacks, a conversion table showing the correspondence between logical addresses and physical addresses based on the internal state of the nonvolatile semiconductor memory when the system is required to be started (when power is turned on) or the like. There is a method of creating (see, for example, Patent Document 1).
JP-A-11-110283 (FIG. 10 etc.)

  However, in order to realize the method described in Patent Document 1, at least all pages where data is written must be read, so that a huge number of read processes occur, and the system The processing speed will be reduced.

  In view of the circumstances as described above, an object of the present invention is to provide a data storage device and a data management method capable of improving the processing speed when reading data from a nonvolatile semiconductor memory.

  In order to solve the above-described problem, a data storage device according to a main aspect of the present invention is a data storage device that is detachable from a host device, and is divided into a plurality of blocks that are erasure units of the data, and Each block is a unit for reading and writing data, and is a nonvolatile semiconductor memory divided into a plurality of pages each having a redundant area, and a first of the pages of the first block of the blocks In the redundant area of the first page where data was last written, the second page of the second page where the second data different from the first data was last written before the first data was written And control means for controlling to store first position information indicating a position on the semiconductor memory.

  Here, the host device is an electronic device such as a PC, an AV device, a game device, a digital still camera, a digital video camera, or a mobile phone, and the non-volatile semiconductor memory is, for example, a NAND memory, and a data storage device Is, for example, a so-called memory card. The first and second data may be written on a plurality of pages, respectively, and the first and second pages are pages where the first and second data are written last. The second page is not a concept indicating only a single page but may be a plurality of different pages. In this case, the second data is a plurality of different data written on each page. The first position information may be a physical page number (physical address) or a logical page number (logical address) as long as the position of the second page can be uniquely identified, or relative to the first page. Information indicating the position may be used.

  According to this configuration, since the position information of the second page where the second data is last written is stored in the redundant area of the first page where the first data is written last, the host By accessing the first page and referring to the position information, the device side can grasp the page position of the second data without performing a read process on the second page. In addition, even when the second data is written on a plurality of pages other than the second page, the page position of the second data is grasped without reading the plurality of pages. Can do. Therefore, the host device can immediately construct address correspondence information indicating the correspondence between the logical address of the data viewed from the host device side and the physical address inside the semiconductor memory based on the position information. The processing speed on the host device side when accessing the data storage device can be significantly improved. In addition, since it is not necessary to prepare the address correspondence information on the semiconductor memory in advance, even if the power supply to the data storage device is interrupted during the processing of the host device, the address information is based on the position information. The address correspondence information can be easily constructed.

  In the data storage device, when the second data is written to a third page immediately after the first page, the control unit is configured to use the third page based on the first position information. The redundant area may be controlled to store second position information indicating a position on the semiconductor memory of the first page where the first data is last written.

  As a result, each time data is written to a new page, new position information can be stored in the redundant area of the page, so that the host device always easily constructs address correspondence information based on the latest position information. be able to.

  In the data storage device, the control means can write the second data in the first block of the blocks when the second data is written after the first data is written. When there is no new page, the second data is written to the fourth page at the head of the second block different from the first block, and the first data is immediately after the fourth page. Write to the fifth page, and store in the redundant area of the fifth page second position information indicating the position on the semiconductor memory of the fourth page where the second data was last written However, the first block may be controlled to be erased.

  Thus, even when the write target block moves, the second position information can be stored in the redundant area of the final write target page in the new block, and the address correspondence information can be constructed.

  A data management method according to another aspect of the present invention is divided into a plurality of blocks which are data erasing units, and each of the blocks is a data read / write unit and each has a redundant area. A data management method in a data storage device having a nonvolatile semiconductor memory divided into pages and detachable from a host device, wherein the first data in each page of the first block among the blocks The semiconductor memory of the second page in which second data different from the first data is written last in the redundant area of the first page written last before the first data is written. Storing first position information indicating a position on the first position, reading the first position information from the redundant area of the first page, the first and second data, Serial and position on the semiconductor memory, and generates the correspondence information indicating a correspondence relationship between the position in the logical space assigned by the host device.

  With this configuration, the host device can immediately access the second data based on the correspondence information generated from the first position information.

  In the data management method, when the second data is written to the third page immediately after the first page, the redundancy information of the third page is stored in the redundant area based on the first position information. , Storing second position information indicating a position on the semiconductor memory of the first page in which the first data was last written, and based on the stored second position information, The correspondence information may be updated.

  In the data management method, the correspondence information is stored in a predetermined storage area of the data storage device or the host device, and the second data is read from the second page based on the stored correspondence information, The correspondence information may be erased from the storage area when the reading is completed.

  As a result, the capacity of the storage area can be minimized.

  In the data management method, when the second data is written after the first data is written, there is no page in which the second data can be written in the first block among the blocks. In this case, the second data is written to the fourth page at the head of the second block different from the first block, and the first data is written to the fifth page immediately after the fourth page. The second position information indicating the position on the semiconductor memory of the fourth page where the second data was last written is stored in the redundant area of the fifth page for writing, and the first page The corresponding information may be updated based on the second position information read from the redundant area of the fifth page.

  As described above, according to the present invention, it is possible to improve the processing speed when reading data from the nonvolatile semiconductor memory.

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

FIG. 1 is a block diagram showing a configuration of a data storage device according to an embodiment of the present invention.
As shown in FIG. 1, the data storage device 10 includes a nonvolatile semiconductor memory 1, a processor 2 as a control unit, an internal RAM 3, a buffer RAM 4, and an interface unit 5. The data storage device 10 is a so-called memory card in the form of a card, for example, and is used as a removable memory that can be inserted into and removed from a host device (not shown) such as a PC or a digital camera.

  The nonvolatile semiconductor memory 1 is composed of a plurality of multi-level cells, and is, for example, a NAND flash memory in which each cell stores four values (2 bits).

  The processor 2 performs data transfer between the internal RAM 3 or the buffer RAM 4 and the nonvolatile semiconductor memory 1 while performing overall control of each block of the data storage device 10, and reads, writes, and erases data.

  The internal RAM 3 is used as a working storage area of the processor 2. For example, an operation control command for the processor 2 transferred from the host device, various parameters necessary for executing the control command, and the data storage device 10. The internal state etc. are temporarily stored. The internal RAM 3 temporarily stores the write data when the data read from the nonvolatile semiconductor memory 1 is written to the nonvolatile semiconductor memory 1 again.

  The buffer RAM 4 functions as a so-called page buffer, temporarily stores write data transferred from the host device side via the interface unit 5, and is read from the nonvolatile semiconductor memory 1 and sent to the host device side via the interface unit 5. The data to be transferred is temporarily stored.

  The interface unit 5 is an interface with the host interface unit 11 of the host device. The interface unit 5 includes, for example, a serial interface that performs data transfer using three signal lines using a serial protocol, and a parallel interface that performs data transfer using six signal lines using a parallel protocol.

FIG. 2 is a diagram showing a configuration of a storage area in the nonvolatile semiconductor memory 1.
As shown in the figure, this storage area is divided into a plurality of blocks (physical blocks) 21 (block 0, block 1...). Each block 21 is a data erasing unit. Each block 21 is divided into a plurality of pages (physical pages) 22 (page 0, page 1,...) That are data write units or read units.

FIG. 3 is a diagram showing the configuration of each page 22 of one block 21.
As shown in the figure, one block 21 is composed of, for example, 16 pages 22, and each page 22 is composed of a plurality of (for example, four) sectors 23 (sectors 0 to 4) that are data (actual data) write areas. It has a sector 3) and a redundant area 24 which is a storage area for error correction codes and other metadata.

FIG. 4 is a diagram showing an example of information stored in the redundant area 24 in the present embodiment.
In the present embodiment, each block 21 is assigned in advance a data ID (for example, A to F) for identifying a plurality of types of data, and each page 22 of each block 21 is assigned the data ID. Only data having any data ID can be written. More specifically, the data ID is associated with a logical block address (LBA: Logical Block Address) of each data in the logical space assigned by the host device. For example, data IDs: A to F correspond to LBAs 0 to 5.

  As shown in the figure, in the redundant area 24 of each page 22, the data ID of the data written in the page 22 and the latest data (last written data) corresponding to each other data ID are stored. Information indicating the position (page number) of the written page 22 is stored. For example, in the example shown in the figure, the data written in page 10 is data having data ID: F, and the latest data of data having other data IDs: A to E are page 5 and page 5, respectively. 8, page 9, page 3, and page 0.

  In each block 21, data having the same data ID may be written on a plurality of pages 22, but the last written data among the plurality of the same data is only written in the redundant area 24. Information indicating the page position is stored. That is, the redundant area 24 stores the maximum page number among a plurality of pages in which the same data is written. In the example of the figure, “x” shown in pages 1, 2, 5 to 7 in the figure indicates that the same data as the data written in those pages is written in the subsequent pages. Show.

  Each data ID may be a numerical value or a character string in addition to the alphabet as long as the data written on the page 22 can be uniquely identified. The information indicating the page position of the latest data corresponding to the other data ID may be a logical page number in addition to a physical page number as long as the page position can be uniquely identified. It may be information indicating the relative position.

FIG. 5 is a diagram showing another example of information stored in the redundant area 24 in the present embodiment.
As shown in the figure, there is a case where data corresponding to all the data IDs assigned to each block 21 does not necessarily exist. In the example shown in the figure, since data corresponding to the data ID: A does not exist in any block 22 in this block 21, information (“nonexistence”) indicating this is stored in the redundant area 24 of the page 10. Is done. Of course, the information indicating that there is no data corresponding to any ID may be a character string or a number.

  Next, operations of the data storage device 10 and the host device configured as described above will be described.

  When the host device accesses (reads / writes) each block 21, the information in the redundant area 24 of the last used (written) page inside each block 21 is read, and all data IDs assigned to each block are read. Correspondence information indicating in which page 22 the data corresponding to is present is generated. In the present embodiment, this correspondence information is referred to as an ID / page map. As a method for searching for the last used page, for example, on the condition whether or not writing has occurred in the redundant area 24 of each page 22, the last page of each block 21 (the page having the largest page number). ) To the previous page in order (linear search), well-known methods such as binary search and tree search are used.

FIG. 6 is a diagram showing an example of the ID / page map.
FIG. 5A shows an ID / page map 61 when data corresponding to all the data IDs assigned to each block 21 exists. In this example, an ID / page map 61 generated based on the redundant area 24 of the page 10 shown in FIG. 4 is shown.

  FIG. 5B shows an ID / page map 61 when there is no data corresponding to one of the data IDs assigned to each block 21. In this example, an ID / page map 61 generated based on the redundant area 24 of the page 10 shown in FIG. 5 is shown.

  The ID / page map 61 is held on a volatile memory (not shown) of the host device or in the internal RAM 3 of the data storage device 10 and is deleted, for example, every time access from the host device is completed. Further, the ID / page map 61 may be held while the host device may access the block 21 in which the ID / page map 61 is generated.

  Next, operations of the host device and the data storage device 10 when there is access (write / read) to the nonvolatile semiconductor memory 1 will be described in more detail.

  FIG. 7 is a flowchart showing an operation when data is written to the nonvolatile semiconductor memory 1.

  As shown in the figure, when writing to each block 21, the host device first determines whether or not an ID / page map 61 already generated for the block 21 exists (step 71). When the ID / page map has not been generated yet (No), the redundant area 24 of the page immediately before the page to be written is read, and the ID / page map 61 is read based on the information stored in the redundant area 24. Generate (step 72).

  Next, the host device updates the generated ID / page map 61 according to the page to be written (step 73). At this time, the data storage device 10 generates information about the data ID and the page position in the redundant area 24 of the page to be written in accordance with the updated ID / page map 61 (step 74).

  Then, the data storage device 10 writes the data designated by the host device and the generated information on the redundant area 24 to the page to be written in the nonvolatile semiconductor memory 1 (step 75).

FIG. 8 is a diagram showing a state in which information in the redundant area 24 of each page is sequentially stored when data is written.
As shown in FIG. 9A, data ID: F is written in the redundant area 24 of page 5 of block N, and the data corresponding to data IDs: A to E are respectively page 1. , Page 2, page 3, page 0 and page 4 are stored. From this state, when data of data ID: A is written to the next page 6, the ID / page map 61 generated based on the information of the redundant area 24 of the page 5 is updated corresponding to the writing. The

  Then, as shown in FIG. 6B, based on the updated ID / page map 61, data of data ID: A is written in the page 6 in the redundant area 24 of the page 6, and Information indicating that data corresponding to the data IDs B to F is written in page 2, page 3, page 0, page 4, and page 5 is stored.

  In this state, when data of data ID: B is written to the next page 7, the ID / page map 61 generated based on the information of the redundant area 24 of the page 6 similarly corresponds to the writing. Updated.

  Then, as shown in FIG. 6C, based on the updated ID / page map 61, data of data ID: B is written in the page 7 in the redundant area 24 of the page 7, and Information indicating that data corresponding to the data IDs A, C to F is written in page 6, page 3, page 0, page 4, and page 5 is stored.

  With the above operation, each time data is written to each page 22, the information in the redundant area 24 of the page 22 to be written is updated, so the host device reads the redundant area 24 of the last used page. Thus, the ID / page map 61 in the block 21 can be immediately constructed, and the correspondence between the logical address and the physical address can be easily grasped.

  If there is no page 22 that can be written in the block 21 (when all pages 22 are written), the data to be written is written to another new block 21 and then written. Data having each data ID other than the target is copied from the old block to the other block 21, and after the copy is completed, the data in the old block 21 is erased. FIG. 9 is a diagram showing how the information in the redundant area 24 of the new block 21 on each page is updated in this case.

  As shown in the figure, when a data write command for data ID: D is generated and there is no writable page in block N, the data storage device 10 first adds the data of the data ID: D. Write to the first page 0 of the correct block M. At this time, an ID / page map 61 corresponding to the writing to page 0 is generated. At the same time, as shown in FIG. 5A, in the redundant area 24 of page 0 of block M, the data written in this page is data ID: D, and other data IDs: A to C , E and F store information indicating that none of the data exists in the block M.

  Subsequently, when the data of the data ID: A is copied to the page 1 of the block M, the generated ID / page map 61 is generated corresponding to the writing to the page 1. At the same time, as shown in FIG. 4B, in the redundant area 24 of page 1 of block M, the data written on this page is data of data ID: A, and the data of data ID: D is page Information indicating that none of the data written in 0 and corresponding to the other data IDs B, C, E, and F exists in the block M is stored.

  Subsequently, when the data of the data ID: B is copied to the page 2 of the block M, the generated ID / page map 61 is generated corresponding to the writing to the page 2 in the same manner. At the same time, as shown in FIG. 5C, in the redundant area 24 of page 2 of block M, the data written on this page is data of data ID: B, and data of data ID: A, D Are written in pages 1 and 0, respectively, and information indicating that none of the data corresponding to the other data IDs B, C, E, and F exists in the block M is stored.

  Even when the data C and E are respectively copied to the pages 3 and 4 of the block M, the ID / page map 61 is updated according to the copy and the information of the redundant area 24 of each page is also updated ( Not shown).

  When the data with the data ID: F is copied to the page 5 of the block M, the generated ID / page map 61 is generated corresponding to the writing to the page 5. At the same time, as shown in FIG. 4D, in the redundant area 24 of page 5 of block M, the data written in this page is data ID: F, and data IDs: A to E Stores information indicating that data has been written to page 1, page 2, page 3, page 0, and page 4, respectively. When the above processing is completed, the block N is erased.

  As described above, even when the block to be written is changed, the information on the redundant area 24 of each page 22 is sequentially written according to the copy processing from the previous block. The ID / page map 61 can be immediately constructed by always grasping the latest page position in which data corresponding to is written. In addition, in the page in the middle of the copy process to the new block (pages 0 to 4 of the block M in the example of FIG. 8), the update process of the ID / page map 61 is performed as long as the information of the redundant area 24 is stored. The ID / page map 61 may be generated only for the last page (the page 5 of the block M in the example of FIG. 8) for which the copy process has been completed.

FIG. 10 is a flowchart showing an operation when reading data written in the nonvolatile semiconductor memory 1.
As shown in the figure, when reading data, the host device first determines whether or not the ID / page map 61 has been generated for the block 21 to be read (step 101), and the ID / page map. If 61 has not been generated (No), the host device searches for the last used page of the block 21 to be written, and generates the ID / page map 61 from the information in the redundant area 24 of the page (step 102). ).

  Then, the host device acquires the page position of the data to be read based on the generated ID / page map 61 (step 103), and stores the data to be read based on the acquired page position in the nonvolatile semiconductor memory. 1 is read out (step 104).

  As described above, the host device can immediately generate the ID / page map 61 from the information in the redundant area 24 of the last used page, and can immediately access desired data.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.

  The information of the redundant area 24 of each page 22 in the above-described embodiment is information indicating the data ID of the data written on the page 22 and the latest page position where the data corresponding to the other data ID is written. However, for example, as shown in FIG. 11, each latest page in which data corresponding to all data IDs assigned to each block 21 is written may be stored.

  In the above-described embodiment, the number of data IDs assigned to each block 21 is six (A to F). However, the number is not limited to this number, and may be changed as appropriate according to the capacity of the redundant area. Is possible.

  In the above-described embodiment, the ID / page map 61 is generated and updated for each block 21, but one ID / page map 61 generated for all the blocks 21 of the nonvolatile semiconductor memory 1 is integrated. The ID / page map 61 may be generated.

It is a block diagram which shows the structure of the data storage device which concerns on one Embodiment of this invention. It is a figure which shows the structure of the storage area of the non-volatile semiconductor memory 1 in one Embodiment of this invention. It is the figure which showed the structure of each page 22 of one block 21 in one Embodiment of this invention. It is the figure which showed an example of the information memorize | stored in the redundant area 24 in one Embodiment of this invention. It is the figure which showed the other example of the information memorize | stored in the redundant area 24 in one Embodiment of this invention. It is the figure which showed the example of ID / page map in one Embodiment of this invention. 4 is a flowchart showing an operation when data is written to the nonvolatile semiconductor memory 1 in one embodiment of the present invention. FIG. 4 is a diagram showing a state in which information in a redundant area 24 is stored when data is written in an embodiment of the present invention. FIG. 6 is a diagram showing how redundant area 24 information is stored when data is written to a new block in an embodiment of the present invention. 4 is a flowchart showing an operation when reading data written in the nonvolatile semiconductor memory 1 in one embodiment of the present invention. It is the figure which showed an example of the information memorize | stored in the redundant area 24 in other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Nonvolatile semiconductor memory 2 ... Processor 3 ... Internal RAM
4 ... Buffer RAM
DESCRIPTION OF SYMBOLS 5 ... Interface part 10 ... Data storage device 11 ... Interface part 11 ... Host interface part 21 ... Block 22 ... Page 23 ... Sector 24 ... Redundant area 61 ... ID / page map

Claims (7)

A data storage device that is detachable from a host device,
A non-volatile semiconductor memory that is divided into a plurality of blocks that are data erasing units, and each block is divided into a plurality of pages that are units for reading and writing the data and each have a redundant area;
Among the blocks, the first data is written in the redundant area of the first page in which the first data is written last in each page of the first block. A data storage device comprising: control means for controlling to store first position information indicating a position on the semiconductor memory of a second page in which different second data is written last. . The data storage device according to claim 1,
The control means, when the second data is written to the third page immediately after the first page, based on the first position information, in the redundant area of the third page, A data storage device that controls to store second position information indicating a position on the semiconductor memory of the first page in which the first data is written last. The data storage device according to claim 1,
The control means is a case where the second data is written after the first data is written, and there is no page in which the second data can be written in the first block among the blocks. In addition, the second data is written to the fourth page at the head of the second block different from the first block, and the first data is written to the fifth page immediately after the fourth page. In the redundant area of the fifth page, second position information indicating the position on the semiconductor memory of the fourth page where the second data was last written is stored, and the first page A data storage device characterized by controlling to erase a block. A nonvolatile semiconductor memory is divided into a plurality of blocks, which are data erasing units, and each block is divided into a plurality of pages, each of which is a unit for reading and writing data and has a redundant area. A data management method in a data storage device detachable from a host device,
Among the blocks, the first data is written in the redundant area of the first page in which the first data is written last in each page of the first block. Storing first position information indicating a position on the semiconductor memory of a second page in which different second data is written last;
The first position information is read from the redundant area of the first page, and the position of the first and second data on the semiconductor memory and the position in the logical space allocated by the host device A data management method characterized by generating correspondence information indicating a correspondence relationship. The data management method according to claim 4,
When the second data is written to the third page immediately after the first page, the first data is stored in the redundant area of the third page based on the first position information. Storing second position information indicating a position on the semiconductor memory of the first page written last,
The correspondence management information is updated based on the stored second position information. A data management method, comprising: A data management method according to claim 4, wherein
Storing the correspondence information in a predetermined storage area of the data storage device or the host device;
Reading the second data from the second page based on the stored correspondence information;
The data management method, wherein the correspondence information is erased from the storage area when the reading is completed. The data management method according to claim 4,
In the case where the second data is written after the first data is written, and there is no page in which the second data can be written in the first block among the blocks, the second data is written. Is written to the fourth page at the beginning of the second block different from the first block,
Writing the first data to a fifth page immediately after the fourth page;
Storing, in the redundant area of the fifth page, second position information indicating a position on the semiconductor memory of the fourth page where the second data was last written;
Erasing the first block;
The data management method, wherein the correspondence information is updated based on the second position information read from the redundant area of the fifth page.

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