JP2008305061A - Memory controller, nonvolatile storage device, and nonvolatile storage system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a memory controller that can be safely used even if the guaranteed number of rewrites to a nonvolatile memory is small, a nonvolatile storage device, and a nonvolatile storage system. <P>SOLUTION: In a multi-write mode, a read/write control part 125 performs a data writing process without deleting data according to an access command from an access device 100. An operational mode setting part 128 is set in a read-only mode in which writes to a nonvolatile memory 130 are disabled when an upper limit M of formatting related to the guaranteed number of rewrites to the nonvolatile memory 130 for which the number of formatting from the access device 100 is predetermined is reached and no deleted block remains. In this way, even if the nonvolatile memory 130 with a small guaranteed number of rewrites is used, the value of the upper limit M of formatting is appropriately set to prevent the nonvolatile memory 130 from being rewritten by more than the guaranteed number of rewrites. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a write multi-type non-volatile storage device including a non-volatile memory, a memory controller that controls the non-volatile memory, and a non-volatile storage system in which an access device is added to the non-volatile storage device as a configuration requirement.

The demand for nonvolatile memory devices including a rewritable nonvolatile memory has been increasing, especially for semiconductor memory cards. Semiconductor memory cards are very expensive compared to optical disks and tape media, but due to the advantages of small size, light weight, earthquake resistance, and ease of handling, recording of portable devices such as digital still cameras and mobile phones The demand as a medium is widespread. This semiconductor memory card includes a flash memory as a nonvolatile main memory, and has a memory controller for controlling the flash memory. The memory controller performs read / write control on the flash memory in response to a read / write instruction from an access device such as a digital still camera or a personal computer main body.

  Such a semiconductor memory card is attached to an access device such as a digital still camera, and is regarded as a removable disk from the access device side and managed by a file system such as a FAT file system. The FAT file system manages file data for each “cluster” using a file allocation table (hereinafter referred to as FAT). In order to use a nonvolatile memory device such as a semiconductor memory card, each cluster is logically erased by first formatting it. When writing file data to the formatted nonvolatile storage device, the file data is allocated to an empty cluster (logically erased cluster), and the file data and the cluster number to which the file data is allocated are allocated. (Logical address) is specified in the nonvolatile storage device. A nonvolatile storage system using such a FAT file system is described in detail in, for example, Patent Document 1.

Flash memory built into products such as non-volatile storage devices and portable audio devices requires a relatively long time for writing to and erasing the memory cell array, which is a storage unit. It can be written or written. The flash memory is composed of a plurality of physical blocks, and each physical block includes a plurality of pages. Erasing is performed in units of physical blocks, and writing is performed in units of pages. The flash memory is divided into a plurality of areas such as an area where data is written (hereinafter referred to as a normal area) and an area where system information is written (hereinafter referred to as a system area).
Japanese Patent Laid-Open No. 2001-188701

  In recent years, a variety of flash memories that can store 2-bit information in one memory cell, such as a multi-level NAND flash memory, has become mainstream in response to demands for large capacity and low cost. Such a multi-level NAND flash memory has a low guaranteed number of rewrites because it is difficult to ensure the reliability of the memory cells. In the conventional binary NAND flash memory, the guaranteed number of rewrites is 100,000 times, for example, whereas in the multi-level NAND flash memory described above, the guaranteed number of rewrites is, for example, 10,000 times. It has dropped to about 1/10. Furthermore, it is difficult to manufacture a flash memory that can guarantee the number of rewrites of 10,000 times, and there is a problem of an increase in cost due to deterioration in the yield of the flash memory. The reality is that some manufacturers of nonvolatile memory devices manufacture and sell products equipped with multi-level NAND flash memories whose rewrite guarantee count is less than 10,000.

  The guaranteed number of rewrites of the flash memory is directly related to the lifetime of the nonvolatile memory device. Conventionally, a user who uses a nonvolatile storage device has thought that the nonvolatile storage device is semi-permanent. However, when a flash memory having a small number of guaranteed rewrites, for example, 100 times is used for a nonvolatile storage device, there has been a problem that it cannot be used suddenly.

In such a non-volatile storage device including a flash memory with a small number of rewrite guarantees and having a capacity of 4 GB, when recording is performed for 1 hour per week at a recording rate of 4 Mbytes / second, 4 GB per week is obtained according to equation (1). Rewriting occurs about 3.5 times for the entire area.
(1 × 3600 seconds / week) ÷ (4 GB ÷ 4 MB / second) = about 3.5 times / week (1)
Therefore, the life of the semiconductor memory card is suddenly exhausted after using it for about 28 weeks according to the equation (2).
100 times / 3.5 times / week = about 28 weeks (2)

  Even if the lifetime can be predicted in advance, the conventional nonvolatile memory device is widely recognized by users as being semi-permanent, and there is a risk of causing social confusion as a quality problem.

  In view of the above problems, the present invention provides a memory controller, a nonvolatile storage device, and a nonvolatile storage system that can use a nonvolatile storage device that uses a nonvolatile memory with a small number of guaranteed rewrites. The purpose is to do.

  The nonvolatile storage device proposed in the present invention can format a nonvolatile memory a plurality of times, and after each format, writes data to each physical block without erasing data (hereinafter referred to as a mode). The nonvolatile memory device has two modes, a write multimode and a read only mode (hereinafter referred to as a read-only mode), and is switched from the write multimode to the read-only mode.

  In order to solve this problem, a memory controller of the present invention is a memory controller that writes data to a nonvolatile memory and reads data from the nonvolatile memory in accordance with an access instruction from the outside. An erasure processing unit that erases all user data stored in the non-volatile memory according to the format instruction and executes formatting, and a write process that reads data without erasing data according to an access instruction from the outside. A read / write control unit that performs read processing, and a write multi-mode capable of writing and reading data if the cumulative number of formats of the nonvolatile memory is equal to or less than a predetermined format upper limit number of times, reaching the upper limit number of formats, When there is no more free space in the non-volatile memory Serial prohibits writing to non-volatile memory, in which includes an operation mode setting unit that sets a read only mode to enable reading only, the.

In order to solve this problem, a nonvolatile memory device of the present invention is a nonvolatile memory device that writes and reads data according to an external access instruction, and the nonvolatile memory device includes a nonvolatile memory, A memory controller that writes data to the nonvolatile memory and reads data from the nonvolatile memory in accordance with an external access instruction, the memory controller in accordance with a format instruction from the outside An erasure processing unit for erasing all user data stored in and executing formatting;
In accordance with an external access instruction, a write process for writing data without erasing the data, a read / write controller for performing a read process for reading the data, and the cumulative number of formats of the nonvolatile memory is less than or equal to a predetermined maximum number of formats If this is the case, write multi-mode in which data can be written and read, the upper limit number of formats has been reached, and writing to the non-volatile memory is prohibited when the non-volatile memory has run out, and only reading is possible. And an operation mode setting unit for setting to a read-only mode.

  In order to solve this problem, a nonvolatile storage system according to the present invention is a nonvolatile storage system having an access device and a nonvolatile storage device that writes and reads data according to an access instruction from the access device. The nonvolatile memory device includes a nonvolatile memory, and a memory controller that writes data to the nonvolatile memory and reads data from the nonvolatile memory in accordance with an access instruction from the access device. The memory controller erases all user data stored in the non-volatile memory in accordance with an external format instruction and executes a format, and performs data without erasing data in accordance with an external access instruction. Read processing to write data, read processing to read data If the cumulative number of formats of the write control unit and the nonvolatile memory is equal to or less than the predetermined format upper limit number of times, the write multi-mode capable of writing and reading data is set, and the format upper limit number of times is reached and the nonvolatile memory is free. And an operation mode setting unit for prohibiting writing to the nonvolatile memory when the capacity runs out and setting to a read-only mode that enables only reading.

  Here, a capacity parameter generation unit that indicates the recordable capacity in the nonvolatile memory may be further provided.

  Here, a format request unit that indicates the format request to the outside in accordance with the data recording state of the nonvolatile memory may be further provided.

  Here, the operation mode setting unit indicates to the outside that it is a write-once mode in which data can be read and data can be written last when the cumulative number of formats reaches a predetermined maximum number of formats. It may be.

  Here, at least one of the cumulative number of formats executed by the erasure processing unit, the remaining number of formats until the upper limit number of formats is reached, and the ratio of the cumulative number of formats to the upper limit number of formats is generated, and the format shown to the outside You may make it further provide a parameter production | generation part.

  According to the present invention, the operation mode setting unit sets the mode for prohibiting writing to the nonvolatile memory (read only mode) when the number of formatting reaches the predetermined format upper limit number of times, and further reads and writes. Since the control unit performs data write processing without erasing data in accordance with an external access instruction, for example, even if a nonvolatile memory with a guaranteed number of rewrites of 100 is used, the format upper limit number of times is set. By setting the value to the number of guaranteed rewrites or less, that is, 100 or less, it is possible to prevent the nonvolatile memory from being rewritten 100 times or more. That is, it is possible to reliably avoid a situation in which the lifetime of the nonvolatile storage device is exhausted during use.

  In addition, if the operation mode setting unit indicates to the outside that the write-once mode is indicated when the number of formatting reaches the upper limit of formatting, the write-once mode in which writing immediately after the formatting can be written at the end The user can recognize that there is. For this reason, it is possible to take measures such as recording only the data to be permanently stored in the nonvolatile storage device in the write-once mode.

(Embodiment)
FIG. 1A is a block diagram showing a nonvolatile storage system according to an embodiment of the present invention, and FIG. 1B is a block diagram showing an access device thereof. 1A and 1B, the nonvolatile storage system includes an access device 100 and a nonvolatile storage device 110. In the present invention, the nonvolatile memory device 110 is a write multi type nonvolatile memory device. This non-volatile storage device erases each physical block of the non-volatile memory only at the time of formatting, and when the data is updated on the access device side, the non-volatile storage device does not erase the data, but sequentially stores data in new physical blocks. When the free space is exhausted, formatting is continued by reformatting the nonvolatile memory device from the initial state, and the number of times of formatting is limited. The access device 100 and the nonvolatile storage device 110 are connected by a bus 1. The nonvolatile storage device 110 includes a memory controller 120 and a nonvolatile memory 140. The memory controller 120 and the nonvolatile memory 140 are connected via the bus 2.

  The memory controller 120 includes a host interface 121, a buffer 122, a memory interface 123, a CPU unit 124, a read / write control unit 125, a format request unit 126, an erasure processing unit 127, an operation mode setting unit 128, a format parameter generation unit 129, and a capacity parameter generation. Part 130.

  The host interface 121 is a block that receives commands, logical addresses, and data related to data writing and reading from the access device 100, and transmits data to the access device 100 when data is read.

  The buffer 122 is used to absorb the difference between the data transfer rate of the bus 1 and the data transfer rate of the bus 2. The size of the buffer is assumed to be twice the size of a register 141 in the nonvolatile memory 140 described later, here 4 kbytes.

  The memory interface 123 is a block for writing data temporarily stored in the buffer 122 to the nonvolatile memory 140 and reading data stored in the nonvolatile memory 140 to the buffer 122.

  The CPU unit 124 is a block that controls the entire memory controller 120.

  The read / write control unit 125 writes and reads data to and from the nonvolatile memory 140 based on commands from the access device 100. The read / write control unit 125 has two read / write control modes, a write multi-mode and a read-only mode. A case where the number of remaining formats is 0 in the write multi-mode is particularly referred to as a write-once mode. The read / write control unit 125 includes a physical area management table that indicates the usage state of each physical block in the nonvolatile memory 140, and a volatile RAM that stores a logical physical conversion table for converting a logical address into a physical address. This table will be described later. Further, as shown in FIG. 2, the read / write control unit 125 has a memory type table for storing the memory capacity, physical block size, guaranteed number of rewrites, etc. corresponding to the ID code as a ROM. The read / write control unit 125 generates a physical address of the nonvolatile memory 140 based on the logical address received from the access device in the write multi-mode, writes data or reads the data, and reads the data in the read-only mode. It controls to read data from the corresponding physical address.

  In FIG. 2, the non-volatile memory whose ID code is 0x0 or 0x4 corresponds to a binary NAND flash memory with a large number of guaranteed rewrites, and the guaranteed number of rewrites is 100,000. A nonvolatile memory whose ID code is 0x1 or 0x5 corresponds to a multi-value NAND flash memory with a large number of guaranteed rewrites, and the guaranteed number of rewrites is 10,000. On the other hand, the non-volatile memory whose ID code is the value 0x2 or the value 0x6 is a binary NAND flash memory with a small number of rewrites, and the number of rewrite guarantees is 1000. In addition, the non-volatile memory whose ID code is 0x3 or 0x7 is a multi-value NAND flash memory with a small number of rewrites, and the rewrite guarantee number is 100 times. The number of guaranteed rewrites is determined by a shipment test of the nonvolatile memory manufacturer, and the number of guaranteed rewrites of the nonvolatile memory varies.

  The format request unit 126 holds a threshold value D (for example, 0) of the number of erased physical blocks in the nonvolatile memory when formatting is started, and the number of erased blocks in the normal area of the nonvolatile memory 140 is the threshold value D. This is a block for outputting a format request to the access device 100 when

  The erase processing unit 127 is a block that executes formatting by erasing the normal area of the nonvolatile memory 140 when a format instruction is transferred from the access device 100.

  The operation mode setting unit 128 is a block for setting the read / write mode of the read / write control unit 125 according to the number of formats described later. At first, the write multi mode is set. When the number of formatting reaches the upper limit, the write once mode in the write multi mode is set, and when there is no room for writing to the physical block in the write once mode, the read only mode is switched. It also has a function of outputting to the access device 100 which mode is in effect.

  The format parameter generation unit 129 is a block having a function of generating parameters related to the format and storing them in the nonvolatile memory 140. The format parameter will be described later.

  The capacity parameter generation unit 130 counts the number of erased blocks by checking the block status of a physical area management table to be described later, generates a recordable capacity based on the number of erased blocks and a physical block size to be described later, and is recordable The capacity is output to the access device 100 as a capacity parameter. Further, the capacity parameter generation unit 130 stores the number of erased blocks and the recordable capacity in the nonvolatile memory 140.

  The nonvolatile memory 140 includes a register 141, a memory cell array 142, and a control circuit 143. The register 141 is a volatile RAM having a size equal to the size of a page which is a writing unit to be described later, and temporarily holds data transferred from the memory interface 123. The memory cell array 142 is a flash memory having a capacity of 1 Gbyte, for example, and is composed of a plurality of physical blocks.

  FIG. 3 is a diagram showing the configuration of the memory cell array 142. The memory array 142 has a capacity of 1 GB, for example, and is composed of physical blocks from 0 to 4095 (PB0x0 to PB0xfff, where 0x represents a hexadecimal number). As shown in FIG. 4, each physical block is composed of 128 pages with physical page numbers PPN0 to 127. Of these, the data area is 2 kbytes per page. In addition, it has a management area of 64 bytes per page. Data transferred from the normal access device 100 is stored in the data area of each page. An ECC code for error correction is stored in the management area. A physical block is an erasing unit, and a page is a writing unit. The data area size of each physical block is 256 kbytes. The size of the register 141 is 2 kbytes according to the capacity of the page.

  The control circuit 143 is a circuit that holds an ID code 144 for identifying the nonvolatile memory 140 and controls the register 141 and the memory cell array based on a write command and a physical address transferred from the memory interface 123. The ID code 144 is a code that can identify the type of the nonvolatile memory 140, and is stored in advance in the ROM or the like of the control circuit 143 when the flash memory is manufactured. The ID code 144 may be written in advance in a partial area in the memory cell array 142.

  FIG. 5 is a diagram showing a memory map showing the correspondence between the logical address space and the physical address space of the nonvolatile memory 140. Here, the physical address space is composed of 4096 blocks as described above, and among these, a normal area 145 for 3815 blocks, a register area 146 for 10 blocks, a system area 147 for 129 blocks, and a spare area 148 for 82 blocks. have. These areas are formed by an initialization process described later. A parameter holding block 149 is provided in the register area 146.

  The physical block in the system area 147 stores the physical area management table (for 1 kbyte) shown in FIG. 6 and the logical physical conversion table (for 6 kbyte) shown in FIG. The physical area management table indicates the block status of each physical block corresponding to each physical block number PBN, that is, a valid block, a defective block, and an erased block by two bits of 00, 10, and 11, respectively. The logical physical conversion table is a table for converting the logical block number LBN into the physical block number PBN. These tables are copied to the RAM of the read / write controller 125 when the power is turned on.

  FIG. 8 is a diagram showing the parameter holding block 149. In this physical block, the format parameter is stored in the physical page number PPN, and the capacity parameter is stored in the physical page number PPN1. The format parameters include a lower-order byte of page number PPN0, that is, format cumulative number F, format upper limit number M, remaining format number R, and format rate X arranged in ascending order from byte number 0. The capacity parameter has a lower byte of page number PPN1, that is, a recordable capacity arranged in ascending order from byte number 0, and the number of erased blocks.

  Here, the cumulative number of formats F is the number of times the format has been instructed from the access device 100, and the maximum format number M is a value determined in accordance with the guaranteed number of rewrites in the nonvolatile memory 140, the remaining number of formats. R is the number of formatting until the format upper limit number M is reached. The format rate X is a ratio of the cumulative format number F to the format upper limit number M. The number of erased blocks is the total number of blocks that have been erased in physical blocks in a normal area, which will be described later, and the recordable capacity is the total number of erased blocks in the data area size of each physical block. For example, a value obtained by multiplying 256 kbytes.

  On the other hand, the access device 100 is a device that writes data to and reads data from the nonvolatile storage device 110. As shown in FIG. 1B, the access device 100 includes an application unit 101, a file system unit 102, a driver unit 103, a receiving unit 104, and a display unit 105. The receiving unit 104 includes a format request receiving unit 104a, a format parameter receiving unit 104b, a mode receiving unit 104c, and a capacity parameter receiving unit 104d.

  The application unit 101 is a block that transmits data to the file system unit 102 in accordance with a user's recording operation and receives data from the file system unit 102 in accordance with a user's playback operation. The file system unit 102 is a block that allocates data transmitted from the application unit 101 in the logical address space and transfers data read from the nonvolatile storage device 110 to the application unit 101. The processing of the file system unit 102 can be realized using, for example, a general technique disclosed in Patent Document 1 and the like, and thus description thereof is omitted. The driver unit 103 is a circuit for interfacing the file system unit 102 and the nonvolatile storage device 110.

  The format request receiving unit 104a is a block that prompts the file system unit 102 to format when the format request flag transferred from the format request unit 126 is received. The format parameter receiving unit 104 b is a block that receives parameters relating to the format transferred from the format parameter generating unit 129 and causes the display unit 105 to display these parameters. When the mode receiving unit 104c receives the mode information for the read / write control transferred from the operation mode setting unit 128, the mode receiving unit 104c is a block for displaying the mode information on the display unit 105. The capacity parameter receiving unit 104 d is a block that receives the capacity parameter related to the recordable capacity transferred from the capacity parameter generating unit 129 and displays the parameter on the display unit 105.

  The nonvolatile storage system of the present embodiment configured as described above will be described in an initial state, an initialization process at power-on, and a data write process at normal operation.

[initial state]
First, the contents of initialization processed by the nonvolatile memory device manufacturer before shipping the nonvolatile memory device 110 will be described. FIG. 5 shows the correspondence between the logical address space managed by the access device 100 and the physical address space of the nonvolatile storage device 110. The logical address space is narrower than the physical address space. Prior to shipment of the nonvolatile memory device, defective blocks are examined in advance by a rewrite test of the entire area of the nonvolatile memory 140. The defective block found at this point is called an “initial defective block”, and the physical block number of the defective block is managed. In the subsequent process, the block status of the corresponding physical block number in the physical area management table of FIG. 6 is set to a defective block.

  Next, after erasing the entire area, system information such as secure information is stored in the system area 147 of FIG. Further, the physical area management table (for 1 kbyte) shown in FIG. 6 and the logical physical conversion table (for 6 kbyte) shown in FIG. 7 are stored in physical blocks that are not defective blocks in the system area 147. In the physical area management table, the block status of a bad block is set to a value of 10, and the block status of a physical block that is not a bad block is set to a value of 11. 0xfff is set in each row of the logical-physical conversion table. The register area 146 stores attribute information as a nonvolatile storage device (semiconductor memory card), for example, card capacity (size of a normal area described later).

  The sizes of the register area 146 and the system area 147 vary depending on the type of the nonvolatile storage device, but in this embodiment, the register area 146 is 10 blocks (2560 kbytes), and the system area 147 is 129 blocks (33024 k). Bytes).

The normal area 145 is an area for storing so-called file data such as images and music data sent from the access device 100 and management information (FAT information, etc.) for managing the file data. The size of the normal area is 3815. When the size of the block, that is, the size of the physical block is 256 kbytes, it becomes 976640 kbytes. File data and management information are collectively referred to simply as data. The spare area 148 is an area secured as a replacement destination of a defective block when a defective block occurs in writing to each area. The spare area 148 preferably has a capacity of 2% or more with respect to the size of the entire area. The reason is based on the provision of the number of guaranteed rewrites by the flash memory manufacturer. For example, the guaranteed number of times of 10,000 means that the defective block size generated by rewriting 10,000 times is less than 2% of the size of the entire area. In the present embodiment, 82 blocks are reserved as the spare area 148 from the equation (3) by the round-up process.
(1 Gbyte / 256 kbytes) x 2% ≒ 82 blocks (3)

  However, depending on the type of nonvolatile storage device, the size of the register area 146 and the system area 147 may be relatively large, and the spare area 148 may be smaller than 82 blocks.

  If data writing and formatting are repeated, the entire spare area 148 is used up, and data cannot be recorded as a nonvolatile storage device. In order to manage this time, a parameter holding block 149 for holding parameters relating to the format and recording capacity is provided in the final physical block of the register area 146. When viewed from the access device 100, the parameter holding block 149 is arranged at the last logical block number in the logical address space, that is, LBN = 3824. Accordingly, 3824 (hexadecimal 0xefd) is stored as the physical block number PBN at the position where the logical block number LBN of the logical-physical conversion table shown in FIG. 7 is 3824.

  Next, data in the parameter holding block 149 will be described. The cumulative format number F is 0 in the initial state, and is incremented by 1 by the format parameter generation unit 129 in accordance with a format instruction from the access device 100 in an initialization process described later. The format upper limit number M is a value determined by the nonvolatile storage device manufacturer with reference to the guaranteed number of rewrites in the memory type table shown in FIG. Usually, it is preferably less than the value of the number of guaranteed rewrites. The remaining format count R is the format count until the format upper limit count M is reached.

  In the present embodiment, it is assumed that a nonvolatile memory having an ID code value of 0x3 is used in the memory type table shown in FIG. 2, and the format upper limit number M is 100 times the same as the guaranteed number of rewrites. Accordingly, in the initial state, the format cumulative number F is 0, the format upper limit number M is 100, the remaining format number R is 100, and the format rate X is 0.

  Next, capacity parameter data will be described. In the initial state, all physical blocks that are not initially defective are erased blocks, so the value of the number of erased blocks is a value obtained by subtracting the initial defective block from 3815 blocks that are the number of physical blocks in the normal area. The available capacity is a value obtained by multiplying the value of the number of erased blocks by the physical block size of 256 kbytes.

[Initialization at power-on]
When the access device 100 is turned on, the nonvolatile storage device 110 is also turned on via the bus 1 and the nonvolatile storage device 110 shifts to an initialization process. In the initialization process, the CPU unit 124 temporarily holds the physical area management table and the logical physical conversion table stored in the system area 147 via the memory interface 123 in the volatile RAM inside the read / write control unit 125. Thereafter, in reading and writing data, the physical address is determined using these tables temporarily stored in the RAM. Further, when each table is updated, it is written back to the nonvolatile memory 140 each time as a countermeasure against power interruption.

  Next, when the format cumulative number F is 0, the format processing and the operation of each unit related to the format processing are performed according to FIG. First, when the cumulative format number F stored in the parameter holding block 149 is 0 (S100), the control is transferred to the format request unit 126. The format request unit 126 transfers the format request flag and the normal area size (976640 kbytes) stored in the register area 146 to the access device 100 (S101).

  When the format request receiving unit 104a in the access device 100 receives the format request flag and the normal area size, the user is requested to confirm the format, and if the confirmation is obtained, a format instruction is issued to the file system unit 102 (S102). ). The file system unit 102 formats the nonvolatile storage device 110 (S103). Note that the formatting method by the access device 100 can be realized by using a general technique as shown in, for example, Patent Document 1, and thus the description thereof is omitted here.

  When the CPU unit 124 receives a format end notification on the file system side from the access device 100, the CPU 124 transfers control to the erasure processing unit 127 and the read / write control unit 125, and the erasure processing unit 127 erases all physical blocks that are not defective blocks in the normal area. (S104). After this erasure process is completed, the read / write control unit 125 updates the block status that is a valid block in the internal physical area management table so that it becomes an erased block (S105), and the physical area management table is nonvolatile. Is written back to the memory 140 (S106).

Next, the format parameter generation unit 129 increments the cumulative format number F stored in the parameter holding block 149 shown in FIG. 8 by 1 and decrements the remaining format count R by 1. The format parameter generation unit 129 calculates the format rate X based on Expression (4) and updates those values (S107).
X = F / M (4)

The capacity parameter generation unit 130 counts the number of erased blocks in the normal area based on the physical area management table in the read / write control unit 125, calculates the recordable capacity based on the equation (5), and updates those values ( S108).
Recordable capacity = number of erased blocks x physical block size (5)
A series of processing from S101 to S108 is referred to as S109.

  FIG. 10 shows the operation of each part related to the operation mode setting. The operation mode setting unit 128 compares the cumulative format number F with the format upper limit number M (S200). When F is less than M, the operation mode setting unit 128 sets the read / write control unit 125 to the write multimode and The read / write control mode is set as a write multimode in the register (S201). If the format cumulative number F is not less than M in S200, it is determined in S202 whether the format cumulative number F and the format upper limit number M are equal. If these values are equal, the presence or absence of an erased block is determined in S203. If there is an erased block, the operation mode is set to the write-once mode in S204. If there is no erased block, the read / write controller 125 is set to the read-only mode (S205). If the cumulative format number F is not equal to the format upper limit number M in S202, error processing is performed (S208).

  Further, the operation mode setting unit 128 transmits mode information specifying the light multi-mode to the access device 100 (S206), and the reception unit 104 of the access device displays the received mode information on the display unit 105 ( S207). In this way, the user can recognize that normal reading and writing is possible in the light multi-mode. In the write-once mode, data can be written only once, so that the user can write only important data to the nonvolatile memory device. When the read-only mode is displayed, data can no longer be written, so that only reading is executed. The read / write control mode receiving unit 104c may recognize the current read / write control mode by appropriately referring to the read / write control mode information set in the register in the operation mode setting unit 128. Absent. Finally, the CPU unit 124 clears all of the buffer 122 and notifies the access device 100 that initialization has been completed.

[Processing during normal operation]
A normal operation after the above-described initialization process will be described with reference to the flowchart of FIG. In the following description, the read / write control mode is assumed to be the write multi mode. In step S300, the capacity parameter generation unit 130 outputs the recordable capacity to the access device 100. The application unit 101 of the access device 100 recognizes the recordable capacity. On the other hand, the nonvolatile storage device 110 waits for a data write command or read command from the access device 100 (S301). If there is an access, it is determined whether the command is a write command (S302). Thereafter, when a read command is sent from the access device 100 to the nonvolatile memory device 110, a read process for reading data corresponding to the logical address given in S303 is performed.

  The application unit 101 writes data satisfying the recordable capacity via the file system unit 102. When a write command is received (S302), it is checked whether the current control mode is a read-only mode (S304). If the read-only mode is not set, the CPU 124 shifts the control to the read / write control unit 125, and the read / write control unit 125 checks the block status from PBN0 to PBN3814 in ascending order in the physical area management table shown in FIG. The erased block is acquired, and the physical block to which new data is written is determined (S305). Then, new data is written into the acquired erased block via the memory interface 123 (S306). The block status of the PBN storage position of the acquired erased block in the physical area management table is set to the value 00 (valid block) (S307), and the acquired erased block is stored in the LBN storage position of the new data in the logical physical conversion table. The PBN of the block, that is, the new data write destination PBN is recorded (S308), and the physical area management table and the logical physical conversion table are written back to the nonvolatile memory 140 (S309). With the above processing, data writing is completed.

  Next, the format request unit 126 checks the block statuses of PBN0 to PBN3814 in the physical area management table in the read / write control unit 125, and determines whether the number of erased blocks is equal to or less than a predetermined threshold D. If the number of erased blocks is equal to or less than the threshold value D, the process proceeds to S101 in FIG. 9 to execute format processing (S311). Next, the above-described operation mode setting process of FIG. 10 is executed (S312). Here, the threshold value D is stored in the ROM in the format request unit 126, but the ROM may be a RAM and the threshold value D may be set from the access device 100 side. If the number of erased blocks exceeds the predetermined threshold value D in S310, the processes in S311 and S312 are not executed.

  As described above, according to the nonvolatile storage system shown in the embodiment of the present invention, the read / write control unit 125 performs the data write process without erasing the data in accordance with the access instruction from the access device 100. The mode setting unit 128 prohibits writing to the nonvolatile memory 140 when the number of formatting from the access device 100 reaches the predetermined format upper limit number M related to the guaranteed number of rewrites of the nonvolatile memory 140 and there are no erased blocks. The read-only mode was set. Thus, for example, even if the nonvolatile memory 140 having the guaranteed number of rewrites of 100 is used, the nonvolatile memory 140 is set to 100 times by setting the value of M to the guaranteed number of times of rewrite, that is, a value of 100 or less. It is possible to prevent overwriting. That is, it is possible to reliably avoid a situation in which the lifetime of the nonvolatile storage device is exhausted during use.

  In addition, the operation mode setting unit 128 notifies the access device 100 that the write once mode is in effect or makes the access device 100 refer to it when the cumulative format count F from the access device 100 reaches the format upper limit number M. As a result, the user can recognize that the mode is the write-once mode immediately after the last format. Accordingly, it is possible to take measures such as recording only data that is to be permanently stored in the nonvolatile storage device in the write-once mode.

  In the access device 100, the format request receiving unit 104a, the format parameter receiving unit 104b, the read / write control mode receiving unit 104c, and the capacity parameter receiving unit 104d receive various parameters from the nonvolatile storage device 110. However, various parameters held in the nonvolatile storage device 110 and the nonvolatile memory 140 may be read from these blocks.

  In addition, the format request unit 126 requests the access device 100 to format, but the access device 100 may start formatting based on the recordable capacity received by the capacity parameter receiving unit 104d. .

  In this embodiment, the operation mode is notified to the access device. However, the operation mode may be recognized by access from the access device. Further, the format parameter and the capacity may be recognized from the outside based on an external access without outputting the format parameter to the outside. Further, in this embodiment, the write-once mode is set when the number of formatting reaches the upper limit number. However, the write-once mode may be switched immediately before the upper limit number M of formatting.

  The non-volatile storage system according to the present invention proposes a method that can use a non-volatile memory with a small number of guaranteed rewrites with peace of mind, and uses various non-volatile storage devices such as semiconductor memory cards and the like. This is useful in a still image recording / reproducing apparatus, a moving image recording / reproducing apparatus, or a mobile phone.

It is a block diagram which shows the non-volatile storage device of the non-volatile storage system in embodiment of this invention. It is a block diagram which shows the access apparatus of the non-volatile storage system in embodiment of this invention. 4 is a memory map showing a memory type table included in the read / write control unit 125. It is a memory map which shows a response | compatibility with a logical address space and a physical address space. 3 is an explanatory diagram showing physical blocks that constitute a memory cell array 142. FIG. It is explanatory drawing which shows the structure of a physical block. 4 is a memory map showing a physical area management table included in the read / write control unit 125; 3 is a memory map showing a logical-physical conversion table included in a read / write control unit 125. It is explanatory drawing which shows the structure of a parameter holding block. It is a flowchart which shows the operation | movement of each part which concerns on a format process and a format process. It is a flowchart which shows operation | movement of each part which concerns on operation mode setting. It is a flowchart which shows the normal process of a non-volatile storage device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Access apparatus 101 Application part 102 File system part 103 Driver part 104 Receiving part 104a Format request receiving part 104b Format parameter receiving part 104c Read / write control mode receiving part 104d Capacity parameter receiving part 105 Display part 110 Non-volatile storage device 120 Memory controller 121 Host Interface 122 Buffer 123 Memory interface 124 CPU unit 125 Read / write control unit 126 Format request unit 127 Erase processing unit 128 Operation mode setting unit 129 Format parameter generation unit 130 Capacity parameter generation unit 140 Non-volatile memory 141 Register 142 Memory cell array 143 Control unit 144 ID Code 145 Normal area 146 Register area 147 System area 148 Spare area 149 Parameter holding block

Claims (15)

A memory controller that writes data to a nonvolatile memory and reads data from the nonvolatile memory according to an external access instruction,
An erasure processing unit for erasing all user data stored in the nonvolatile memory according to an external format instruction and executing formatting;
A read / write controller that performs a write process for writing data without erasing the data, and a read process for reading data, according to an external access instruction;
When the cumulative total number of formats of the nonvolatile memory is less than or equal to a predetermined format upper limit number of times, a write multimode in which data can be written and read is set, and when the format upper limit number of times is reached and the free space of the nonvolatile memory is exhausted A memory controller comprising: an operation mode setting unit for prohibiting writing to the non-volatile memory and setting to a read-only mode that enables only reading.   The memory controller according to claim 1, further comprising a capacity parameter generation unit that indicates a recordable capacity in the nonvolatile memory to the outside.   The memory controller according to claim 1, further comprising a format request unit that indicates a format request to the outside in accordance with a recording state of data in the nonvolatile memory.   The operation mode setting unit indicates to the outside that the mode is a write-once mode in which data can be read and data can be written last when the cumulative number of formats reaches a predetermined format upper limit number of times. The memory controller according to any one of?   Generate at least one of the cumulative number of formats executed by the erasure processing unit, the remaining number of formats until the upper limit number of formats is reached, and the ratio of the cumulative number of formats to the upper limit number of formats, and generate format parameters shown to the outside The memory controller according to claim 1, further comprising a unit. A nonvolatile storage device that writes and reads data according to an external access instruction,
The nonvolatile memory device is
Non-volatile memory;
A memory controller that writes data to the nonvolatile memory and reads data from the nonvolatile memory in accordance with an external access instruction;
The memory controller is
An erasure processing unit for erasing all user data stored in the nonvolatile memory according to an external format instruction and executing formatting;
A read / write controller that performs a write process for writing data without erasing the data, and a read process for reading data, according to an external access instruction;
When the cumulative total number of formats of the nonvolatile memory is less than or equal to a predetermined format upper limit number of times, a write multimode in which data can be written and read is set, and when the format upper limit number of times is reached and the free space of the nonvolatile memory is exhausted And a non-volatile memory device comprising: an operation mode setting unit for prohibiting writing to the non-volatile memory and setting to a read-only mode that enables only reading. The memory controller is
The non-volatile storage device according to claim 6, further comprising a capacity parameter generation unit that indicates a recordable capacity to the non-volatile memory to the outside. The memory controller is
The nonvolatile storage device according to claim 6, further comprising a format request unit that indicates a format request to the outside in accordance with a recording state of data in the nonvolatile memory.   The operation mode setting unit externally indicates that the mode is a write-once mode in which data can be read and data can be written last when the cumulative number of formats reaches a predetermined format upper limit number of times. The non-volatile memory device in any one of -8.   The system further comprises a format parameter generation unit that generates at least one of the cumulative number of formats, the remaining number of formats until the upper limit number of formats is reached, and the ratio of the cumulative number of formats to the upper limit number of formats. The nonvolatile memory device according to any one of 6 to 8. A nonvolatile storage system having an access device and a nonvolatile storage device that writes and reads data according to an access instruction from the access device,
The nonvolatile memory device is
Non-volatile memory;
A memory controller that writes data to the nonvolatile memory and reads data from the nonvolatile memory in accordance with an access instruction from the access device;
The memory controller is
An erasure processing unit for erasing all user data stored in the nonvolatile memory according to an external format instruction and executing formatting;
A read / write controller that performs a write process for writing data without erasing the data, and a read process for reading data, according to an external access instruction;
When the cumulative total number of formats of the nonvolatile memory is less than or equal to a predetermined format upper limit number of times, a write multimode in which data can be written and read is set, and when the format upper limit number of times is reached and the free space of the nonvolatile memory is exhausted And a non-volatile storage system comprising: an operation mode setting unit for prohibiting writing to the non-volatile memory and setting to a read-only mode that enables only reading. The memory controller is
The nonvolatile storage system according to claim 11, further comprising a capacity parameter generation unit that notifies the access device of a recordable capacity in the nonvolatile memory or refers to the access device. The memory controller is
The nonvolatile storage system according to claim 11 or 12, further comprising a format request unit that notifies the access device of a format request or makes a reference from the access device according to a recording state of data in the nonvolatile memory.   12. The operation mode setting unit indicates to the outside that the mode is a write-once mode in which data reading and last writing of data are possible when the cumulative number of formats reaches a predetermined format upper limit number of times. The non-volatile storage system in any one of -13.   The system further comprises a format parameter generation unit that generates at least one of the cumulative number of formats, the remaining number of formats until the upper limit number of formats is reached, and the ratio of the cumulative number of formats to the upper limit number of formats. The non-volatile storage system according to any one of 11 to 14.

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