JP2006285976A - Nonvolatile storage system, nonvolatile storage device, and data reading method and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that data reading by a data block including an error generation bit cannot be carried out when the number of error generation bits in a data holding block in a nonvolatile storage device is beyond error correction ability supported by the nonvolatile storage device. <P>SOLUTION: The nonvolatile storage device 100A has a controller 101A and a flash memory 102. The flash memory stores user data and an error correcting code for correcting an error in the user data. When there is a read command from the outside, the user data and error correcting code are read from the flash memory. If there is any correctable error in the read user data, error correction is performed and then the data is outputted. If there is uncorrectable error, the data is outputted directly without any correction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a non-volatile storage system, a non-volatile storage device, and a data reading method thereof characterized by reading data from a non-volatile storage device, particularly when a written file is damaged by an error such as data retention failure And a data reading program.

  In recent years, a nonvolatile memory device equipped with a nonvolatile memory has expanded its market as a memory card for a digital camera or a mobile phone. As the storage capacity of the memory card increases, its use has expanded from recording a small capacity such as a data file or still image to recording a moving picture that requires a larger capacity.

However, the NAND type flash memory mainly used as a non-volatile memory of a memory card inherently has a possibility of data retention error. For this purpose, an error correcting code (hereinafter also referred to as ECC) is added to the data to be recorded and written to the flash memory, and at the time of reading, the data is corrected based on the error correcting code, Data is guaranteed when a data retention error occurs.
JP 2003-316661 A

  However, if a data retention error exceeding the ECC correction capability occurs, the data cannot be corrected. The memory card does not output the data of the management unit including not only the bit in which the error has occurred but also the bit considered to be illegal. In that case, data is lost in the management unit including the bit. Therefore, when the nonvolatile memory is used for data recording of a digital camera, a part of valuable still image or moving image data photographed by the user is greatly lost, or the data itself is lost. However, in practice, even if an error occurs in some bits of still image or video data, it is often possible to obtain an image that is almost similar to the original still image. Often done. For this reason, it is considered that reading data has a great significance even if it is data in which a bit error has occurred, compared with the loss of data itself.

  When the number of error occurrence bits in the data holding block of the nonvolatile storage device is larger than the error correction capability supported by the nonvolatile storage device, the data is read in block units including the bit in which the error has occurred. There is a problem that cannot be done.

  In order to solve this problem, a nonvolatile storage system according to the present invention includes a nonvolatile storage device and an access device that accesses the nonvolatile storage device and reads user data of the nonvolatile storage device. The nonvolatile storage device is a nonvolatile memory having a user data area for writing user data and a management area for storing an error correction code for performing error correction of data written in the user data area; An error correction circuit that corrects an error of user data read from the nonvolatile memory based on an error correction code of the management area, reads the user data from the nonvolatile memory, and if there is an error, the error correction circuit Is used to perform error correction, and if there is no error, the error correction read is read as it is, and the user is read from the nonvolatile memory. A controller having raw data reading for outputting the data as it is, and the access device reads user data from the nonvolatile storage device using the error correction reading and the raw data reading. Is used to read user data.

  In order to solve this problem, a nonvolatile storage device of the present invention includes a user data area in which user data is written and a management area in which an error correction code for performing error correction of data written in the user data area is stored. A non-volatile memory device, and a controller including an error correction circuit that corrects an error of user data read from the non-volatile memory based on the error correction code. If there is no error, the data in the user data area is output as is. If the error is correctable, the error in the data in the user data area is corrected and output. If there is an error that cannot be corrected, the data is output. If there is no error, the normal read mode will not output the data in the user data area and the error will be correctable. The outputs correct data errors in the user data area, if there is an uncorrectable error is obtained by a special read mode is output as the data of the user data area.

  In order to solve this problem, the data reading method of the present invention has a user data area for writing user data and a management area for storing an error correction code for performing error correction of data written in the user data area. User data is read from a non-volatile storage device including a non-volatile memory and a controller including an error correction circuit that corrects an error of user data read from the non-volatile memory based on an error correction code in the management area A method for reading data, wherein user data is read from the non-volatile memory, whether there is an error in the user data read from the non-volatile memory, output if there is no error in the user data, and output if there is an error If the error correction circuit is used to perform error correction and output, and the error correction circuit cannot be used to correct the error, The user data read from the nonvolatile memory and outputs it.

  In order to solve this problem, a data reading program of the present invention has a user data area for writing user data and a management area for storing an error correction code for performing error correction of data written in the user data area. User data is read from a non-volatile storage device including a non-volatile memory and a controller including an error correction circuit that corrects an error of user data read from the non-volatile memory based on an error correction code in the management area A data read program, wherein the controller corrects user data read from the non-volatile memory using the error correction circuit and outputs the user data using normal read output to the outside of the volatile storage device. An error that cannot be corrected by the error correction circuit occurs in the nonvolatile memory, and the normal reading If it is determined that the data cannot be read, the controller uses the ECC off read to output the user data read from the nonvolatile memory as it is to the outside of the volatile storage device without using the error correction circuit. Is read out.

  In order to solve this problem, a data reading program of the present invention has a user data area for writing user data and a management area for storing an error correction code for performing error correction of data written in the user data area. User data is read from a non-volatile storage device including a non-volatile memory and a controller including an error correction circuit that corrects an error of user data read from the non-volatile memory based on an error correction code of the management area A data reading program that corrects and outputs user data read from the non-volatile memory when an error that can be corrected is output to the non-volatile storage device, and is read from the non-volatile memory when an error is not possible. User data is read out by special reading that outputs raw data.

  According to the nonvolatile memory system, the nonvolatile memory device, the data reading method thereof, and the data reading program of the present invention, an error exceeding the error correction capability installed in the nonvolatile memory device occurs in the nonvolatile memory device. Even in a state where the data cannot be read after correcting the error, the data in the nonvolatile memory device can be read by performing the read without using the error correction. Or it can be read incompletely.

  Embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a non-volatile storage device according to Embodiment 1 of the present invention, and FIG. 2 is a block diagram showing an example of an access device. In FIG. 1, a memory card 100A is a nonvolatile storage device, and data is written to and read from the memory card 100A by the access device 120. The memory card 100A and the access device 120 constitute a nonvolatile storage system. The memory card 100A includes a controller 101A and a flash memory 102 that is a nonvolatile memory. In the controller 101A, the host I / F 111 is an interface between the access device 120 and the controller 101A, and the flash I / F 112 is an interface between the flash memory 102 and the controller 101A. The control circuit 113 controls each block in the controller 101A so as to write the write data from the access device 120 to the flash memory 102 and read the data in the flash memory 102 to the access device 120. The page buffer 114 is a buffer that temporarily stores data transferred from the access device 120 and written to the flash memory 102 or data read from the flash memory. Here, the capacity of the page buffer 114 is 2 kB (bytes). The ECC circuit 115 adds an error correction code calculated based on the write data when writing data from the access device 120 to the flash memory 102, and temporarily reads data from the flash memory 102 to the access device 120. This is an error correction circuit that performs error correction on the data read to the page buffer 114 using ECC. The ECC switching flag 116 is a flag for holding information for switching between an ECC on mode in which data is read after error correction and an ECC off mode in which data is read without performing ECC correction.

  Next, the access device 120 will be described with reference to FIG. The access device 120 includes a CPU 121, an input device 122, a display device 123, a storage device 124, and a memory card I / F 125 that control the entire device. The memory card I / F 125 includes a command control unit 126, a write control unit 127, and a read control unit 128, and controls the interface of the memory card. For example, when the access device 120 is a digital camera, a shutter, a button that can be operated by the user, and a CCD for inputting image data become the input device 122, and a liquid crystal panel becomes the display device 123. The command control unit 126 issues a command to the memory card 100A, and the write control unit 127 and the read control unit 128 are used as control units when writing data to the memory card and reading data, respectively.

  When the access device 120 reads data from the memory card 100 </ b> A, the data is read from the memory card using the command control unit 126 and the read control unit 128 based on the data read program installed in the CPU 121. When the access device 120 writes data to the memory card 100, the data is written to the memory card using the command control unit 126 and the write control unit 127 based on the data write program installed in the CPU 121.

  The flash memory 102 is a non-volatile memory that holds user data, and includes a large number of physical blocks that are erase units. Each physical block consists of a plurality of pages. FIG. 3 is a diagram showing a data structure of a page unit which is a unit of writing and reading of the flash memory 102. Each page includes a user data area 201 having a capacity of 2 kB (bytes) and a management area 202 having a capacity of 64 B. The user data area 201 is an area in which user data sent from the access device 120 is written as it is. The management area 202 is an area in which user data management information is written, and includes an ECC 203 for performing error correction on the user data. User data is divided into user data areas (2 kB) and written to the flash memory 102. The unit to be divided is 2 kB here, but is not particularly limited, and 512B, which is an access unit from the access device 120 in general, may be used, or other capacity may be used.

  First, the case where the access device 120 reads data from the memory card 100A will be described with reference to FIGS. 4 is a flowchart showing the operation of the access device 120, and FIG. 5 is a flowchart showing the operation of the memory card 100A. First, in a state where the memory card 100A is connected to the access device 120 and the power is turned on, the control circuit 113 sets the ECC switching flag 116 to the ECC on mode. This is the standard state. The access device 120 designates a logical address and issues a read command to the memory card 100A. Here, the data reading unit is a sector unit, and the variables m and n are sector unit variables. The sector may have the same capacity as the physical block described above, or may be different from this. In step S01, the variable m is set to the first sector of the data to be read, and the variable n is set to 0. Next, in step S02, the data of sector m is read in the ECC on mode.

  On the other hand, the memory card 100A receives a read command from the access device 120 (step S11). The host I / F 111 notifies the control circuit 113 of the read command and the logical address information from the access device 120. The control circuit 113 determines the physical address of the flash memory 102 in which the data of the logical address is written, and notifies the flash I / F 112 of the information and the read execution instruction. The flash I / F 112 issues a read command to the flash memory 102. Thus, data is read from the target sector of the flash memory 102 (step S12). Among them, the data in the user data area 201 is transferred to the page buffer 114 and the ECC circuit 115. Thereafter, the flash I / F 112 transfers the ECC 203 included in the management area 202 only to the ECC circuit 115. After the transfer is completed, the control circuit 113 obtains information on the error from the ECC circuit 115, and determines whether there is an error (step S13). If there is no error, the data in the page buffer 114 is output as it is to the access device 120 via the host I / F 111 (step S17). If there is a correctable error, the ECC circuit 115 corrects the error in the page buffer 114 (steps S14 and S15). Thereafter, the process proceeds to step S17, and the data in the page buffer 114 is output to the access device 120 via the host I / F 111. Thus, the access device 120 can read data from the memory card 100A.

  On the other hand, if an error that cannot be corrected has occurred, the control circuit 113 determines the ECC switching flag 116 in step S16. Initially, since this flag is ECC on, the reading process is terminated without outputting data, and the data in the page buffer 114 is not output to the access device 120.

  On the other hand, the access device 120 determines whether or not an uncorrectable ECC error has occurred in the data of sector m in the determination step S03 shown in FIG. As described above, when data is output from the memory card 100A, no error is detected, and when no data is output, an error is determined by inquiring the status to the memory card 100A.

  The control circuit 113 of the memory card 100A notifies that an ECC error that cannot be corrected has occurred via the host I / F 111. In response, the access device 120 issues a correction non-use command to the memory card 100A so as to output without performing error correction. In response to the command, the control circuit 113 sets the ECC switching flag 116 to an ECC off mode for reading data without performing error correction.

  In this state, the access device 120 issues a read command again to read data that could not be read due to an error in step S04. On the memory card 100A side, the processing of steps S11 to S14 of FIG. 5 is repeated for the read command of the access device 120, and the ECC switching flag 116 is determined in step S16. Since this flag is off, the control circuit 113 outputs the data in the page buffer 114 as it is to the access device 120 via the host I / F 111 without performing data correction (step S17). This is called ECC off reading.

  In this way, data is output regardless of whether there is an error. In the access device 120, the data read immediately before in step S05 is stored in the image file Im (n). In step S06, it is determined whether or not the sector processed immediately before is the last sector of data to be read. When it is determined that it is the last sector, the file acquisition process is terminated, and when it is determined that it is not the last sector, the process proceeds to step S07. In step S07, the variables m and n are respectively incremented, and then the process returns to step S02 to repeat the same processing. Through the above processing, data can be read out completely or incompletely, and a sector including an error can be recognized.

  6A, 6B, and 6C are diagrams showing the effect of this embodiment. FIG. 6A is assumed to be error-free image data written in the flash memory. When a part of the image data is lost due to a bit error, the conventional memory card can read only the data before the occurrence of the error. Therefore, when this image is displayed, the image is as shown in FIG. 6B, and the image is greatly damaged. On the other hand, when data is read regardless of whether or not an error has occurred as in the present embodiment, even if error correction cannot be performed on the portion where the error has occurred, for example, the number 300 in FIG. As shown in FIG. 5, the original image can be almost reproduced only by damaging only a part of the image. Also, if this data is video data, even if an error occurs and the error cannot be corrected, it is possible to reproduce almost the original moving image only by momentary image disturbance. .

(Embodiment 2)
Next, a second embodiment of the present invention will be described. FIG. 7 is a block diagram showing a configuration of the nonvolatile memory device according to the present embodiment, and the same portions as those in the first embodiment are denoted by the same reference numerals. In this embodiment, the memory card 100B includes a memory controller 101B and a flash memory 102. In the memory controller 101B, the ECC output permission flag 131 is a flag indicating whether or not to permit data output without error correction using an error correction code. The control circuit 132 holds a program for performing processing to be described later. In the second embodiment, the ECC output permission flag 131 permits data output without using ECC error correction, and when the ECC correction function can be automatically used in the memory card 100B, ECC correction is performed. It is output and output as it is when ECC correction cannot be performed.

  Next, the operation of the second embodiment will be described with reference to the flowcharts of FIGS. In the data reading process of the access device, as shown in FIG. 8, in order to read data, first, in step S21, the variable m is set to the head sector of the data to be read, and the variable n is set to zero. Variables m and n are sector unit variables. In step S22, the data of sector m is read out. Here, it is assumed that reading without error correction is permitted. In step S23, the data read from the sector m is stored in the image file Im (n). In step S24, it is determined whether the sector processed immediately before is the last sector of the data to be read. If it is determined that the sector is the last sector, the data reading process is terminated. If it is determined that the sector is not the last sector, the process proceeds to step S25, and after the variables m and n are incremented, the process returns to step S22.

  On the other hand, the memory card 100B receives a read command from the access device 120 as shown in FIG. 9 (step S31). The host I / F 111 notifies the control circuit 132 of a read command and information on the logical address from the access device 120. The control circuit 132 determines the physical address of the flash memory 102 in which the data of the logical address is written, and notifies the flash I / F 112 of the information and the read execution instruction. The flash I / F 112 issues a read command to the flash memory 102. Thus, data is read from the target sector of the flash memory 102 (step S32). Among them, the data in the user data area 201 is transferred to the page buffer 114 and the ECC circuit 115. Thereafter, the flash I / F 112 transfers the ECC 203 included in the management area 202 only to the ECC circuit 115. After the transfer is completed, the control circuit 132 obtains information on the error from the ECC circuit 115, and determines whether there is an error (step S33). If there is no error, the data in the page buffer 114 is output as it is to the access device 120 via the host I / F 111 (step S37). If there is a correctable error, the ECC circuit 115 corrects the error in the page buffer 114 (steps S34 and S35). Thereafter, the process proceeds to step S 37, where the data in the page buffer 114 is output to the access device 120 via the host I / F 111.

  If correction is not possible in step S34, the process proceeds to step S36. Then, with reference to the ECC output permission flag 131, it is determined whether or not output without correction is permitted. If output without correction is permitted, the process proceeds to step S37 to output data, and if output without correction is not permitted, the process ends without reading data. When the output without correction is not permitted, it is the same as that of the conventional memory card. When the output without correction is permitted, the access device 120 can read data from the memory card 100B in a complete or incomplete form. it can.

  The nonvolatile storage system, nonvolatile storage device, data read method, and read program according to the embodiment of the present invention read the same sector without performing error correction in addition to the normal read mode for performing error correction. By providing two types of read modes, a special read mode, data can be read out powerfully.

  As described above, the data reading method and the reading program of the nonvolatile memory device according to the present invention can be applied to a nonvolatile device used in a digital camera or a digital video camera portable device that handles still image data or moving image data. it can.

Block diagram of the nonvolatile memory device according to Embodiment 1 of the present invention 1 is a block diagram showing a configuration of an access device according to Embodiment 1 of the present invention. FIG. 3 is a data configuration diagram of a page of the flash memory according to the first embodiment of the present invention. The flowchart which shows the data reading of the access apparatus in Embodiment 1 of this invention The flowchart which shows the data reading in the memory card in Embodiment 1 of this invention The figure which shows the picture written in the flash memory Diagram showing the image that was read when the error occurred The figure which shows the image after the data reading in Embodiment 1 Block diagram of a nonvolatile memory device according to Embodiment 2 of the present invention Flowchart showing data read of access device in embodiment 2 of the present invention. Flowchart showing data reading of the memory card in the second embodiment of the present invention

Explanation of symbols

100A, 100B Memory card 101A. 101B Controller 102 Flash memory 111 Host I / F
112 Flash I / F
113, 132 Control circuit 114 Page buffer 115 ECC circuit 116 ECC switching flag 120 Access device 131 ECC output permission flag

Claims (12)

A nonvolatile storage system comprising: a nonvolatile storage device; and an access device that accesses the nonvolatile storage device and reads user data of the nonvolatile storage device,
The nonvolatile memory device is
A non-volatile memory having a user data area for writing user data and a management area for storing an error correction code for performing error correction of data written in the user data area;
An error correction circuit that corrects an error in user data read from the nonvolatile memory based on an error correction code in the management area; reads the user data from the nonvolatile memory; And a controller having an error correction read that reads as it is if there is no error and a raw data read that outputs user data read from the nonvolatile memory as it is,
The access device is:
A non-volatile storage system that reads user data from the non-volatile storage device by combining the reading of user data using the error correction reading and the raw data reading. The access device is:
2. The nonvolatile storage system according to claim 1, wherein the error correction reading is used by instructing the nonvolatile storage device, and the user data is read by switching to raw data reading when the error correction cannot be performed. The access device is:
The user data is read using the error correction reading, and it is determined that an error that cannot be corrected by the error correction circuit is generated because no data is output from the nonvolatile storage device. Non-volatile storage system. The controller is
3. The nonvolatile storage system according to claim 2, further comprising a flag for identifying whether or not correction using an error correction code is performed, and switching between the error correction reading and the raw data reading by the flag. A non-volatile memory having a user data area for writing user data and a management area for storing an error correction code for performing error correction of data written in the user data area;
A non-volatile storage device comprising: a controller including an error correction circuit that corrects an error of user data read from the non-volatile memory based on the error correction code,
The controller is
If there is no error, the data in the user data area is output as is. If the error is correctable, the error in the data in the user data area is corrected and output. If there is an error that cannot be corrected, the data is output. Normal read mode that does not output
If there is no error, the data in the user data area is output as it is. If the error is correctable, the error in the data in the user data area is corrected and output. If there is an uncorrectable error, the user is output. A non-volatile storage device having a special read mode for outputting data in a data area as it is. The controller is
6. A flag for identifying whether or not data output is permitted without using error correction, and the controller switches between the normal read mode and the special read mode according to a value of the flag. Non-volatile storage device.   The non-volatile memory device according to claim 5, wherein the flag is switched from outside the non-volatile memory device. A non-volatile memory having a user data area for writing user data and a management area for storing an error correction code for performing error correction of data written in the user data area;
And a controller including an error correction circuit that corrects an error of user data read from the non-volatile memory based on an error correction code of the management area. And
Read user data from the non-volatile memory,
Determine whether there is an error in the user data read from the non-volatile memory,
If there is no error in the user data, it is output as is,
If there is an error, perform error correction using the error correction circuit and output,
A data reading method for outputting user data read from the nonvolatile memory as it is when an error cannot be corrected by using the error correction circuit. A non-volatile memory having a user data area for writing user data and a management area for storing an error correction code for performing error correction of data written in the user data area;
And a controller including an error correction circuit that corrects an error in user data read from the nonvolatile memory based on an error correction code of the management area. And
The controller corrects user data read from the non-volatile memory using the error correction circuit and reads out the user data using normal reading output to the outside of the volatile storage device,
User data read from the nonvolatile memory by the controller without using the error correction circuit when an error that cannot be corrected by the error correction circuit occurs in the nonvolatile memory and cannot be read by the normal reading. A data read program for reading user data using ECC off read which outputs the data as it is to the outside of the volatile storage device.   10. The data read program according to claim 9, wherein the normal read and the ECC off read are switched for each sector.   An error that cannot be corrected by the error correction circuit occurs in the nonvolatile memory when data is not output from the nonvolatile memory device in reading using the normal reading, and it is determined that the data cannot be read by the normal reading. 9. The data reading program according to 9. A non-volatile memory having a user data area for writing user data and a management area for storing an error correction code for performing error correction of data written in the user data area;
And a controller including an error correction circuit that corrects an error in user data read from the nonvolatile memory based on an error correction code of the management area. And
A special data output to the non-volatile storage device if the error can be corrected by correcting the user data read from the non-volatile memory and outputting the raw data read from the non-volatile memory if no error is possible. A data read program for reading user data by reading.

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