JP2010015222A - Memory card - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent destruction of important data due to an occurred recording error when a multi-value NAND flash memory is used. <P>SOLUTION: The memory card includes: n pieces (n is an integer of ≥2) of nonvolatile memory modules (221-224) which constitute a storage area; and a controller which controls read or write of data to the n pieces of memory modules. The n pieces of memory modules is subjected to striping for every predetermined size. A controller of the memory card arranges data of high update frequency to any one of the memory modules (221-224) in order of striping of the memory modules from the second to the n-th. In the data of high update frequency, at least one of the pieces of information on number of times of rewriting, rewrite data volume, the number of rewrite blocks and a degree of consumption to a rewrite lifetime to the memory card is contained. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an information recording medium, and more particularly to a memory card using a nonvolatile memory element.

  In recent years, memory cards with built-in rewritable non-volatile memory elements such as flash memory are becoming widespread, and the type of flash memory used for the memory card is a large-capacity and low-cost multi-value NAND flash memory. I'm starting. However, as described in Patent Document 1, when a recording error occurs when data is written in a certain recording area, the multi-level NAND flash memory is not only the recording area but also the data held in another recording area. However, there is a problem that the data may change (data may be corrupted).

  As described in Patent Document 1, the area where data is destroyed at the time of a recording error is affected by the relationship of pages sharing memory cells, the sharing range of memory cells, and the like. Therefore, which recording area data is destroyed when a recording error occurs differs depending on the internal configuration of the memory card and the control method of the internal controller.

  Various types of memory cards are installed in host devices such as personal computers and camera devices. However, the host device cannot grasp the internal configuration of each memory card and the control method of the internal controller. If an error occurs when the host device records data on the memory card, it is difficult for the host device to predict whether the data in the recording area in the memory card other than the recording area where the error occurred has been corrupted. . From the perspective of the host device, it is possible to grasp only the extent that data at some address may have been randomly destroyed when a recording error occurs.

  Data such as video recorded on a memory card is generally managed as a file by a file system. The file system manages the size of individual files, the date and time of recording update, the usage status and availability of recording areas such as clusters and sectors, and records these as file management information on a recording medium along with data such as video. . Since the host device with the memory card attached accesses desired data using this file management information, the file management information is important information.

  In addition, a memory device such as a flash memory has an upper limit on the number of times that data can be rewritten, and has a rewriting life. If the count value of the number of rewrites, such as how many times the memory card has been rewritten so far, is held in the memory card, the rewrite life of the card can be managed.

  However, it is complicated for the host device to update the count value of the number of times of rewriting the memory card, and it is more convenient for the controller inside the memory card to automatically update the rewrite count value. The host device only needs to write data to the memory card, and if the controller in the card automatically adds and updates the value according to the amount of data written from the host and the number of writes to the count value in the memory card. good.

Based on the above background art, a conventional memory card will be described with reference to FIG.
When the memory card 300 is attached to a host device such as a personal computer or a memory camera, a data write command or a data read command from the host device is instructed to the controller 310 via the interface 330. The controller 310 interprets a command from the host device, accesses the necessary memory modules 321 to 324, and controls data exchange between the host device and the memory module. When there is a data write command from the host device, the controller 310 not only records the data sent from the host device via the interface 330 in the memory modules 321 to 324 but also counts the number of rewrites at an appropriate timing. Update the value.

  In many cases, the controller 310 has a configuration in which a control operation can be programmed, or a CPU is built in the controller 310. For this reason, the control program of the controller 310 is stored in, for example, the separate memory module 340, and when the memory card 300 is activated, the controller 310 loads the program from the separate memory module 340 and starts the control operation.

What is necessary is just to store the program of the controller in a memory card, the count value of the above-mentioned rewrite frequency, etc. in another memory module 340. However, if these data are stored in the memory modules 321 to 324, the separate memory module 340 becomes unnecessary, and the cost of the memory card can be reduced. However, the following problems occur in this case.
JP 2006-318366 A

  When a multi-level NAND flash memory is used for the memory module of the memory card, if a recording error occurs when updating the count value of the number of rewrites stored in the same multi-level NAND memory module, the data in other recording areas There is a possibility of breaking. If the corrupted data is the file management information of the file system, the host device cannot access the desired file data. Further, when the corrupted data is a control program for the controller in the memory card, the controller becomes inoperable and the data stored in the memory card becomes inaccessible.

  An object of the present invention is to solve this problem and prevent even important data from being broken when a recording error occurs even when a multi-level NAND flash memory is used.

  A first memory card according to the present invention includes n (n is an integer of 2 or more) nonvolatile memory modules constituting a storage area, and a controller that controls writing and reading of data to the n memory modules. Including. In the memory card, n memory modules are striped every predetermined size. The controller arranges frequently updated data in any one of the second to nth memory modules in the striping order of the memory modules. The frequently updated data includes at least one of information on the number of times of rewriting to the memory card, the amount of rewriting data, the number of rewriting blocks, and the degree of consumption with respect to the rewriting life.

  A second memory card according to the present invention includes n (n is an integer of 2 or more) nonvolatile memory modules constituting a storage area, and a controller that controls writing and reading of data to the n memory modules. Including. In the memory card, n memory modules are striped every predetermined size. Highly important data such as program data for operating the controller is stored in at least one of the n memory modules. The controller arranges at least one of the number of rewrites to the memory card, the amount of rewrite data, the number of rewrite blocks, and the degree of consumption with respect to the rewrite life in a memory module different from the memory module storing the program data.

  According to the present invention, data having a high update frequency such as the number of times of rewriting of a memory card is arranged avoiding the head of the stripe, so even if a recording error occurs when a multi-level NAND flash memory is used, the stripe unit Data at the beginning of is protected. Therefore, the risk of destruction of the file entry is reduced by protecting the top area of the folder such as file system management information.

  In addition, because highly important data such as program data required to operate the controller of the memory card is placed in a different stripe from data that is frequently updated, there is an effect of reducing the risk of destruction of program data. is there. In order to store data with high update frequency or data with high importance, there is no need to provide a separate memory module for storage, and a memory card can be configured without extra costs.

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

(Embodiment 1)
FIG. 1 is a diagram showing an internal configuration of a memory card according to an embodiment of the present invention. In FIG. 1, a memory card 200 is an interface for communicating between a controller 210 that controls the operation of the memory card 200, memory modules 221 to 224 that store data, and a host device such as a personal computer or a memory camera. 230. The memory modules 221 to 224 are multi-level NAND flash memories. The controller 210 is constituted by a CPU, for example, and realizes a predetermined function by loading and executing program data.

  When the memory card 200 is inserted into the card slot of the host device, a data write / read command is received from the host device via the interface 230. The controller 210 interprets a command from the host device, accesses the necessary memory modules 221 to 224, and controls data exchange between the host device and the memory module. That is, the controller 210 performs writing and reading with respect to the memory modules 221 to 224 in accordance with a command from the host device. Memory modules 221 to 224 are connected in parallel to the controller 210, and the controller 210 can execute data writing and reading with respect to each of the memory modules 221 to 224 at the same time (in parallel). Reading is performed.

  As described above, in order to simultaneously write and read data to and from the memory modules 221 to 224 connected in parallel to the controller 210, it is necessary to sequentially allocate the memory space viewed from the host device to each memory module for each appropriate size. There is. This is generally called “stripe” or “striping”.

  FIG. 2 shows allocation of recording areas of the memory card 200 in the present embodiment. The entire recording area 100 of the memory card is composed of four memory modules 221 to 224. The entire recording area 100 of the memory card is divided into a normal recording area 131 and special recording areas 130 and 132.

  The special recording area 130 includes areas 141 to 144. The area 141 is the top area of the memory module 221, the area 142 is the top area of the memory module 222, the area 143 is the top area of the memory module 223, and the area 144 is the top area of the memory module 224. The special recording area 132 includes areas 151 to 154. The area 151 is the end area of the memory module 221, the area 152 is the end area of the memory module 222, the area 153 is the end area of the memory module 223, and the area 154 is the end area of the memory module 224.

  Areas m0 to m99 are recording areas divided into stripe units, and are composed of four memory modules 221 to 224. The memory space 110 viewed from the host device is composed of areas m0 to m99. The memory space 110 corresponds to the normal recording area 131 of the memory card.

  As described above, the entire recording area 100 of the memory card is composed of the four memory modules 221 to 224. Of these, the remaining portions excluding the head portions 141 to 144 and the tail portions 151 to 154 of the memory modules 121 to 124 are opened to the host device as the normal recording area 131. The normal recording area 131 appears as a memory space 110 from the host device. The host device can access the memory space 110 using a normal write command or read command. On the other hand, the special recording areas 130 and 132 are areas that cannot be accessed by a normal write command or read command from the host device. Only when the host device issues a special command such as a vendor unique command, the special recording areas 130 and 132 can be accessed.

  In the normal recording area 131, four memory modules 221 to 224 are striped. For example, if the stripe unit is 8 KB (kilobytes), each of the recording areas m0 to m99 divided into stripe units is an 8 KB recording area. Become. For example, when the host device accesses the memory space 110 in a range of m0 to m3, for example, m0 to m3 are assigned to four different memory modules 121 to 124 in the memory card 200. It becomes possible to operate simultaneously. By this parallel operation, it becomes possible to read and write data at high speed in response to an access instruction of the host device. In this embodiment, the order of striping is the order of the memory module 221, the memory module 222, the memory module 223, and the memory module 224 (the same applies to the following embodiments).

  FIG. 3 is a diagram illustrating a recording area when the memory card 200 is managed by the file system. In FIG. 3, an area 420 is a file system management unit, and file entries 431 to 433 include empty areas 434 to 439.

  Usually, the file system mounted on the host device side manages the recording area of the memory card in a management unit having a predetermined size. The file system management unit 420 has a different name depending on the type of the file system, and is called, for example, “sector” or “cluster”. The size of the management unit 420 varies depending on the file system setting. Here, as an example, the management unit 420 of the file system is called “cluster”, and the size of the management unit 420 is 32 KB. The file system manages the recording area of the memory card 200 in a management unit of one cluster (= 32 KB). In FIG. 2, if the stripe unit of m0 to m99 is 8 KB, one cluster is composed of four stripe units of 8 KB, and one cluster is allocated to different memory modules 221 to 224 by 8 KB. Will be.

  Here, it is assumed that the file system of the host device has a folder (or directory) mechanism for storing a plurality of files. When one folder is assigned to the management unit 420 in FIG. 3, a large number of file entries can be stored in the folder. The file entry is file system management information including various information related to the file, such as the name and size of the file, the date and time of creation and update, and the recording area used. In FIG. 3, the management unit 420 is set as one folder, and file entries 431 to 433 are stored therein. When viewed from the host device, this appears as if three files are stored in one folder. In FIG. 3, areas 434 to 439 are empty areas in the folder, and no file entry exists here.

  Here, the memory card according to the present embodiment has a great feature in a place where data with high update frequency such as a count value of the number of rewrites of the flash memory is arranged. That is, in the memory card of the present embodiment, data with a high update frequency is arranged in the head portion 144 or the tail portion 154 of the memory module 224. These areas 144 and 154 are special areas and cannot be accessed from the host device by a normal read command or write command. Furthermore, these areas 144, 154 are located in the last memory module in the striping order. Below, the effect | action by this arrangement | positioning is demonstrated.

  First, in FIG. 2, the head portion 144 or the tail portion 154 of the memory module 224 is not assigned to the memory space 110 that can be seen from the host device, and therefore is not overwritten by a normal write command. Therefore, if the count value of the number of times of rewriting of this memory card is arranged in the head portion 144 or the tail portion 154, there is no fear that the host device erroneously overwrites the count value. Further, since the head portion 144 and the tail portion 154 are part of the memory module 224, they are areas on the multi-level NAND flash memory. When the controller 210 in FIG. 1 updates the count value of the number of rewrites arranged here, a recording error may occur. In that case, any data on the memory module 224 may be destroyed at the same time. If the count value of the number of rewrites is arranged at the top portion 144 of the memory module 224, it is assumed that a recording error occurs during the update, and the data in the recording area m7 on the same memory module 124 is damaged. Here, as shown in FIG. 3, an area corresponding to m7 is allocated to a folder of the file system, but is a free area where no file entry information exists. Therefore, it can be seen that even if the data in the recording area m7 is corrupted, there is no effect on the existing file access.

  That is, in the memory card of the present embodiment, data with a high update frequency is arranged as far as possible in the striping order, avoiding the top of the striping order. By placing it at the beginning of the stripe, if a recording error occurs, some data on the memory module at the beginning of the stripe may be destroyed, and the file system management unit, in this case, the beginning of each cluster may be destroyed. become. In FIG. 3, for example, there is a high possibility that the areas m0 and m4 are destroyed. When the area m4 is destroyed, the file entries 431 to 433 become invalid data. When the file entry information becomes invalid data, the host device cannot access the file stored in the memory card.

  In this embodiment, the file system management unit is 32 KB, the number of stripes of the memory card is 4 stripes, and the stripe unit is 8 KB. If the number of file entries is 32 bytes, the number of file entries that can be stored in one management unit 32 KB is 32 KB / 32 = 1024. If data with high update frequency, such as the count value of the number of rewrites, is placed at the end in the striping order, it is safe from the first stripe to the last stripe, that is, up to three stripe units. Therefore, data corruption due to a recording error can be avoided up to the number of file entries for three stripes, that is, up to 768 (= 8 KB / 32 × 3) file entries.

  Further, in FIG. 2, when the top portion 144 and the tail portion 154 of the memory module 224 are used for other purposes, data with high update frequency is arranged in the head portion 143 and the tail portion 153 of the memory module 223. Is also possible. In this case, since it is arranged third in the order of striping, the effect of this embodiment can be obtained with respect to the number of file entries for two stripe units. Data corruption due to recording errors can be avoided up to the number of file entries for two stripe units, that is, up to 512 (= 8 KB / 32 × 2) file entries.

  Similarly, even when the file is arranged in the head portion 142 or the tail portion 152 which is the second in the striping order, the number of file entries that can avoid data destruction is reduced, but the effect of this embodiment can be obtained. In this way, if data with a high update frequency is arranged avoiding the top of the stripe, the effect of this embodiment can be obtained.

  The controller 210 controls the stripe units of the memory modules 221 to 224 and the order of striping. The controller 210 also controls which range of each memory module is shown as a memory space to the host device. Then, data that is frequently updated, such as the count value of the number of rewrites, should be placed on a memory module that is not at the top of the striping order and in a region that is not shown as memory space to the host device, avoiding the top of the striping order. To control. Such a control operation of the controller 210 can be implemented as a program such as a CPU built in the controller. Thereby, the operation of the memory card 200 of the present embodiment can be realized.

(Embodiment 2)
Next, a second embodiment of the present invention will be described. The memory card of the present embodiment has the configuration shown in FIG. FIG. 4 shows allocation of recording areas of the memory card of the present embodiment.

  In the present embodiment, a method for arranging program data of the controller 210 of the memory card 200 in a memory module in the memory card 200 will be described. The program data is a program loaded by the controller 210 to execute a desired control operation.

  In FIG. 4, data having a high update frequency such as a count value of the number of rewrites is arranged in the head portion 144 or the tail portion 154 of the memory module 224. The memory module 124 is located at the end of the striping order. The effect of arranging frequently updated data on the last memory module in the striping order is as described in the first embodiment. In this embodiment, when the program data of the controller 210 is arranged, the memory module 224 is avoided and the program data is arranged in any one of the head portions 141 to 143 and the tail portions 151 to 153 of the memory modules 221 to 223. Hereinafter, this operation will be described.

  In the present embodiment, the program data of the controller 210 is arranged in the head portions 141 to 143 and the tail portions 151 to 153 of the memory modules 221 to 223. Since these recording areas are not allocated to the memory space 110 visible from the host device, the host device cannot be accessed by a normal write command or read command. Therefore, it is possible to prevent the host device from overwriting the program data of the controller 210 with invalid data by mistake.

  Furthermore, data with high update frequency, such as the count value of the number of rewrites, is arranged in the top portion 144 and the end portion 154 of the last memory module 224 in the order of striping, so that a recording error occurs when the count value of the number of rewrite times is updated. If this occurs, data in any area on the memory module 124 may be destroyed. However, since the program data of the controller is arranged in the head portions 141 to 143 and the tail portions 151 to 153 of the memory modules 121 to 123, avoiding the memory module 124, the destruction of the program data can be avoided. If the controller program data is normal, the controller 210 functions normally and data access to the memory card 200 from the host device is possible.

  As described above, in this embodiment, highly updated data such as the count value of the number of rewrites and highly important data such as the program data of the controller 210 in the memory card 200 are arranged in memory modules with different stripes. With this method, even when a multi-level NAND flash memory is used, it is not necessary to add parts like a separate memory module, and data can be arranged on a normal memory module, so that the cost of the memory card can be suppressed. .

  In the present embodiment, an example in which four memory modules are striped has been described. However, the number of stripes is not limited to this, and a memory card that forms a plurality of stripes with a plurality of memory modules can be used. The idea of this embodiment can be applied.

  In this embodiment, an example in which specific data is arranged in the head area or the end area of the memory module has been described. However, the present invention is not limited to this, and any area that is not allocated in a normal memory space accessible by the host device may be used. For example, specific data may be arranged in the area even if it is not at the beginning or end of the memory module.

  In the present embodiment, the count value of the number of times the memory card has been rewritten has been described as an example of frequently updated data. However, the present invention is not limited to this, and the memory card operation history, memory card error occurrence log information, memory Updates data that may be updated when using the memory card, such as history information such as the temperature and voltage at which the card was used, individual identification information of the memory card, and information about the manufacturer and owner of the memory card. It is good also as data with high frequency. For these data, there is a possibility that a recording error will occur at the time of updating. Therefore, it is effective to apply the idea of the above embodiment.

  In the present embodiment, the program data of the controller in the memory card has been described as an example of the data having high importance. However, the present invention is not limited to this, and the operation history of the memory card, log information on the occurrence of an error in the memory card, Data with high importance such as history information such as temperature and voltage used, memory card individual identification information, memory card manufacturer and owner information, memory card specification information, etc. It is good. The effect of this embodiment can be obtained by arranging these data in memory modules having different stripes from data with high update frequency.

  In the present embodiment, the expression of the number of times of rewriting the memory card is used. However, the present invention is not limited to this, and the amount of rewrite data of the memory card, the number of rewrite blocks, the degree of consumption with respect to the rewrite life, the remaining number of times that can be rewritten, Any data that can manage the rewritable life of the memory card, such as the remaining rewritable data amount and the remaining rewritable number of blocks, can be treated as equivalent.

  As described above, the memory card of the present invention is used when a memory card is configured by using a memory element such as a multi-level NAND flash memory that may destroy data in other recording areas at the time of a recording error.

The figure which showed the structure of the memory card of embodiment of this invention The figure which showed allocation of the memory area of the memory card of the 1st Embodiment of this invention The figure explaining the recording area at the time of managing the memory card of this embodiment with a file system The figure which showed allocation of the memory area of the memory card of the 2nd Embodiment of this invention Diagram showing the configuration of a conventional memory card

Explanation of symbols

100 Memory card total recording area 110 Memory space viewed from the host device 131 Memory card normal recording area 130, 132 Memory card special recording areas 141-144 Memory module start area 151-154 Memory module end area 200 Memory card 210 Controller 221 to 224 Memory module 230 Interface m0 to m99 Recording area divided into stripe units

Claims (6)

N (n is an integer of 2 or more) nonvolatile memory modules constituting the storage area;
A memory card including a controller for controlling writing and reading of data to and from the n memory modules,
The n memory modules are striped every predetermined size,
The controller receives at least one of the number of times of rewriting, the amount of rewriting data, the number of rewriting blocks, and the degree of consumption with respect to the rewriting life for the memory card from the second to the nth in the striping order of the memory modules. A memory card, which is arranged in any one of the memory modules up to.   The memory module in which at least one of the number of times of rewriting to the memory card, the amount of rewriting data, the number of rewriting blocks, and the degree of consumption with respect to the rewriting life is arranged is the nth memory module in the striping order of the memory modules The memory card according to claim 1, wherein N (n is an integer of 2 or more) nonvolatile memory modules constituting the storage area;
A memory card including a controller for controlling writing and reading of data to and from the n memory modules,
The n memory modules are striped every predetermined size,
Program data for operating the controller is stored in at least one of the n memory modules,
The controller arranges at least one of the number of times of rewriting, the amount of rewriting data, the number of rewriting blocks, and the degree of consumption with respect to the rewriting life in a memory module different from the memory module storing the program data. To
A memory card characterized by that.   The memory card according to claim 3, wherein the memory module in which the program data is arranged is the nth memory module in the striping order of the memory modules. Each of the memory modules has a normal recording area that can be accessed using a normal write command and a read command, and a special recording area that can be accessed only by a predetermined command,
2. The controller arranges at least one of information on the number of rewrites, the amount of rewrite data, the number of rewrite blocks, and the degree of consumption with respect to a rewrite life in the special recording area of the memory module. 5. The memory card according to any one of 4 to 4.   The memory card according to claim 1, wherein the memory module is a multi-level NAND flash memory.

Images