JPH0877081A - File memory system - Google Patents

Abstract

PURPOSE: To provide the file memory system which prevents sector management data in a nonvolatile memory from being rewritten unnecessarily. CONSTITUTION: In the file memory system which stores data in a file, sector by sector, a nonvolatile storage device 5 which is electrically rewritable in block units has sector management data 51 showing use states by sectors. The sector management data are initially set in a volatile storage device 4 from the nonvolatile storage device 5 and a sector table 41 which has its contents updated according to file operation is formed. When the power supply to the volatile storage device 4 is stopped, the contents of the sector management data that the nonvolatile storage device 5 holds are compared in block units with the contents of the sector table 41 and only blocks where mismatching is detected are rewritten into the corresponding contents of the sector table 41.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a file memory system which uses a flash memory as an electrically rewritable nonvolatile semiconductor memory device, and is applied to a memory card used as an auxiliary memory device of a computer, for example. It is an effective technology.

[0002]

2. Description of the Related Art As a file memory system for storing file data in sector units, for example, there is a file memory system using a flash memory. The flash memory can be electrically erased and written in the same manner as an electrically erasable and programmable read only memory (hereinafter simply referred to as an EEPROM), and in that case, all the memory cells can be erased. It has a function of electrically erasing all or a block of memory cells collectively. Further, each block has a capacity of a plurality of sectors or more, and therefore one block includes a plurality of sectors. As a result, when the data in the flash memory is rewritten, the data is erased in block units, and the data in a plurality of sectors included in the block is collectively rewritten. That is, the rewriting unit is made larger than the sector unit. Therefore, when rewriting a sector, if another valid sector exists in the memory block including the sector, the data in the sector cannot be rewritten as it is, and the empty sector is used for the rewriting. Become. Therefore, information indicating validity or invalidity is required for each sector.

Further, since the above flash memory applies a high electric field to the memory cells when erasing and writing data, there is a limit to the number of times data can be rewritten. Flash memory can usually be rewritten several tens of thousands of times, but when rewriting processing is concentrated on a specific block, the number of data rewritings differs between blocks, and the degree of deterioration of storage elements becomes uneven. . As described above, it is necessary to consider not only the number of data rewrites for the flash memory but also the equalization of the number of data rewrites for each block. Therefore, in order to prevent rewriting from concentrating on a specific block, for example, the erase count for each block is recorded, and the contents of a memory block having valid data with a relatively small rewrite count are invalidated with a relatively large rewrite count. Move to a memory block that has data. For that purpose, information that defines the relationship between the memory address of the block in which the data is replaced and the sector is required.

The above-mentioned information indicating validity or invalidity and the information defining the relationship between the address of the replaced memory block and the sector must be held for each sector as sector management data. The sector management data can be updated on the flash memory, but in that case, it is necessary to rewrite not only the sector storing the file but also the sector management data when rewriting the data of the file. The number of times memory is rewritten increases. Furthermore, rewriting the data in the flash memory requires a significantly longer time than reading the data. Therefore, when the sector management data is rewritten on the flash memory, the time required for rewriting the sector management data is added to the data rewriting time of the file, and the rewriting time for the flash memory significantly increases. Furthermore, because of the time required to rewrite the sector management data, an undesired waiting time may occur when rewriting the file data. As a result, it is not a good idea to sequentially update the sector management data stored in the flash memory as the usage status of the sector changes. Therefore, it is desirable to provide a work area in the file memory system separately from the flash memory and update the sector management data in the work area.

As the work area, for example, a pseudo static random access memory (hereinafter referred to simply as PSR) is used.
AM)) can be used. The PSRAM has a work area for updating the sector management data, and the sector management data is transferred from the flash memory to the area to generate a sector table. The sector table is updated in response to changes in sector usage, so the latest sector usage is shown in the sector table. However, the PSRAM is a volatile semiconductor memory device, and the stored data is lost when the power supply is stopped. Therefore, when the power supply to the PSRAM is stopped, the sector management data of the flash memory is rewritten according to the contents of the sector table, and the latest usage status of the sector is stored in the sector management data of the flash memory.

As an example of a document describing a memory card which is an example of a file memory system using a flash memory, "Nikkei Electronics No. 566" issued by Nikkei BP (October 26, 1992).
There are the 86th and 87th terms of.

[0007]

However, in the conventional technique, there are the following problems in rewriting the sector management data stored in the flash memory with the contents of the corresponding sector table. Found by the inventor.

Rewriting the sector management data to the contents of the sector table is carried out in order to reflect the present state of sector utilization of the flash memory in the sector management data. For this reason, rewriting of data is performed in block units. Considering the characteristics of the flash memory, if the block storing the sector management data and the content of the sector table corresponding to the block match, the block is written to the block. No rewriting is necessary. Therefore, if the sector management data is unconditionally rewritten to the contents of the sector table, there is a possibility that a block that should not be originally rewritten may be rewritten. This impedes the reduction of the number of times of rewriting of the flash memory and the reduction of the rewriting time of the sector management data.

An object of the present invention is to prevent wasteful rewriting of sector management data in a non-volatile semiconductor memory device such as a flash memory, and to reduce the number of times of rewriting to a block storing the sector management data. It is to provide a file memory system. Another object of the present invention is to provide a file memory system capable of reducing the data rewriting time of the sector management data of a nonvolatile semiconductor memory device such as a flash memory.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0011]

The outline of the representative one of the inventions disclosed in the present application will be briefly described as follows.

That is, in a file memory system for storing file data in sector units, a nonvolatile semiconductor memory device capable of electrically erasing data in blocks having a storage capacity of a plurality of sectors is used in each sector. Is stored in the sector management data. The volatile semiconductor memory device is provided with an area for storing the sector table in which the sector management data transferred from the nonvolatile semiconductor memory device is initialized and the contents of which are updated in response to a file operation. When the power supply to the volatile semiconductor memory device is stopped, the contents of the sector management data held by the nonvolatile semiconductor memory device are compared with the contents of the sector table in block units, and a mismatch is detected. A control means for rewriting the contents of the sector table corresponding to only the block is provided.

The control means interrupts the comparison operation for the block in which the non-coincidence is detected, rewrites the data, and then corresponds to another block which has not been compared yet and which stores the sector management data. The operation shifts to a comparison operation with the contents of the sector table.

[0014]

According to the above means, when the sector management data of the volatile semiconductor memory device is reflected in the sector management data of the non-volatile semiconductor memory device, only the blocks whose contents do not match are rewritten in block units. This prevents useless data rewriting for a block that originally does not require rewriting, and suppresses an increase in the number of rewriting times and rewriting time for a nonvolatile semiconductor memory device.

Further, the data of the block for storing the sector management data is rewritten to the data of the corresponding sector table at the time when the mismatch is detected.

[0016]

1 is a block diagram of an embodiment of a file memory system according to the present invention. Although not particularly limited, the memory card 1 shown in the figure has an interface adapted to the JEIDA memory card interface, and is replaced by a magnetic storage device such as a hard disk device or a flexible disk device, and an auxiliary storage device of a computer. Is available as. The memory card 1 includes a card interface 2, a microcomputer 3, a pseudo static random access memory (hereinafter also simply referred to as PSRAM) 4, and a flash memory 5, and the whole is mounted on a card substrate.

The microcomputer 3 shown in FIG.
Although not particularly limited, PS includes a central processing unit (not shown) and a memory storing an operation program thereof, and PS
It controls the operation of the RAM 4 and the flash memory 5. The card interface 2 includes an interface controller 21 and a register circuit 22 including a data register DR, a command register CR, and a status register STR, though not particularly limited, and the microcomputer 3 and the PSRAM 4 are connected via the internal bus 6. , Connected to the flash memory 5. The card controller 2 uses the system bus 1 of the host system 10 that further uses the memory card 1 via the interface terminal.
Connected with 3. The PSRAM 4 is used for the sector table 41, the write buffer 42, etc., and is controlled by the microcomputer 3, although not particularly limited thereto.

The flash memory 5 shown in FIG. 1 is a nonvolatile semiconductor memory device that can be electrically rewritten in block units. For example, memory cells composed of insulated gate field effect transistors having a two-layer gate structure are arranged in a matrix. To be done. The control gates of the transistors forming the memory cells are connected to corresponding word lines (not shown), the drains of the transistors are connected to corresponding data lines (not shown), and the sources of the transistors are not shown in common for each block. Each is connected to the source line.

In the flash memory 5, the data writing operation to the memory cell is realized by, for example, applying a high voltage to the control gate and drain and injecting electrons from the drain side to the floating gate by avalanche injection. By this write operation, the threshold voltage of the transistor of the memory cell seen from the control gate is made higher than that of the erased memory cell in which the write operation is not performed. On the other hand, the erase operation is realized, for example, by applying a high voltage to the source and extracting electrons from the floating gate to the source side by the tunnel phenomenon. Therefore, since the erase operation is collectively performed on a plurality of memory cells connected to the same source line, data is erased in block units in the flash memory. By the erase operation, the threshold voltage of the transistor of the memory cell seen from the control gate is lowered.

When rewriting the data stored in the flash memory 5 in this manner, a high voltage is applied to inject or emit electrons into the floating gate of a predetermined memory cell to cause the memory cell to rewrite. The threshold voltage of the transistor is changed. Therefore, the memory cells forming the flash memory 5 are electrically stressed by rewriting the stored data, and the memory element is deteriorated by the electrical stress. Moreover, since the data erasing unit of the flash memory 5 is a block,
When data having a high rewriting frequency concentrates on a specific block, rewriting of the block frequently occurs and deterioration of the memory cell progresses. If a difference occurs in the number of rewrites for each block, the characteristics of the memory cells that make up the flash memory 5 may become non-uniform.

In order to prevent the above-mentioned problem that the characteristics of the memory cells become non-uniform, for example, the number of times data is erased for each block of the flash memory 5 is recorded, and the stored data is moved to increase the difference in the number of times of rewriting. It should be suppressed. In this embodiment, the number of times of erasing data for each block of the flash memory 5 is recorded in the sector management data 51, the microcomputer 3 refers to the sector management data 51 to move the data in the flash memory 5, and the contents of the block are recorded. To suppress the expansion of the difference in the number of rewrites for each block. The sector management data 51
Has information that defines the relationship between the memory address of the block and the sector, and information that indicates whether the sector is valid or invalid. When the data of the block is moved as described above, the correspondence between the address of the replaced block and the sector is reflected in the information defining the relationship between the memory address and the sector. Therefore, by referring to the sector management data 51, it is possible to obtain the validity or invalidity of each sector and the utilization status of the sector such as the memory address of the block storing the sector. When data is written here, data erasing prior to that is performed in block units, and therefore the sector used for writing cannot erase data unless all sectors of the block to which it belongs are invalidated. Therefore, since a block in which valid sectors and invalid sectors are mixed cannot be used for writing, only valid sectors are moved to another block from the above block,
Data of the block is erased.

When performing a file operation on the flash memory 5 such as the above-mentioned data movement, the sector management data 51 is reflected in the change of the utilization status of the sector caused by the rewriting or movement of the data. The data 51 needs to be updated. However, the sector management data 51 stored in the flash memory 5 is
It is not a good idea to directly rewrite the above because it leads to an increase in the number of times of rewriting of the flash memory 5. As a result, the contents of the sector management data 51 are transferred to the PSRAM 4 to generate the sector table 41, and the sector table 41 is used for the above reference and update.

FIG. 2 shows the flash memory 5 and PSRA.
An explanatory view of an example of the storage area of M4 is shown. In the figure, the sector management data 5 is stored in the area 5a of the flash memory 5.
1 is stored. In the area 4a and the area 4b of the PSRAM 4, the sector table 41 and the write buffer 42 are generated by the microcomputer 3, respectively. A procedure for using the sector management data 51 and the sector table 41 will be described with reference to FIG.

The operation of the memory card 1 in this embodiment is instructed by various commands or signals supplied from the host system 10. Therefore, generation and updating of the sector table 41 are also instructed by commands or signals, which are controlled by the microcomputer 3. The command is not particularly limited, but the host CP
It is supplied from U11 to the command register CR via the system bus 13. When the command is supplied, the interface controller 21 notifies the microcomputer 3 that the command should be fetched by an interrupt or the like. As a result, the microcomputer 3
Decodes the above command and controls the register circuit 22, the PSRAM 4 and the flash memory 5 according to the decoding result.

The operation such as power-on and power-off of the memory card 1 is instructed by the host system 10 by a signal (not shown). For example, when the memory card 1 is instructed to be powered on by a signal (not shown), the microcomputer 3 initializes the PSRAM 4. That is, the microcomputer 3 stores the sector management data 5 from the flash memory 5 in the area 4a.
1 is transferred and the sector table 41 is generated. The area 4b of the PSRAM 4 is used as the write buffer 42.

When reading the data of the file stored in the flash memory 5, a desired file name is supplied from the host CPU 11 together with a command instructing the data reading of the flash memory 5. The microcomputer 3 sets a status indicating that the flash memory 5 is in use in the status register STR. Then, the sector number of the file having the file name is searched, and the sector table 41 is referred to based on the acquired sector number. As a result, the memory address of the flash memory 5 designated by the sector number is obtained. The microcomputer 3 reads the data from the flash memory 5 at the above address and transfers it to the data register DR. After the data transfer, the status register STR is set to a status indicating that valid read data exists in the data register DR. The host CPU 11 reads the read data from the data register DR by recognizing the status.

When data is written in the flash memory 5, the host CPU 11 supplies a command for instructing the data writing in the flash memory 5 and the file name of the data. The microcomputer 3 sets a status indicating that the flash memory 5 is in use in the status register STR. The input data supplied from the system bus 13 is temporarily stored in the write buffer 42, and the file having the above file name is searched. In addition, the sector table 41 is referred to obtain the writable empty sector information, and the data stored in the write buffer 42 is written in the empty sector. Then, the contents of the sector table 41 are rewritten to bring the sector into the valid state. After the writing is completed, the status indicating the result is set in the status register STR.

The microcomputer 3 controls the movement of data stored in the flash memory 5 in addition to the operation instructed by the above-mentioned command or signal in order to equalize the number of times of rewriting for each block. For example, when the memory card 1 is in the non-selected state, the sector table 41
And the difference in the number of rewrites for each block is checked. At this time, if the difference in the number of times of rewriting for each block exceeds the specified range, the data of the block with the number of times of rewriting is moved to the block with the number of times of rewriting. For example, data is transferred to the write buffer 42 from a block storing a valid sector having a relatively small number of rewrites, and the data is written to a block storing an invalid sector having a relatively large number of rewrites. In addition, the information of the valid sector is moved from the block in which the valid sector and the invalid sector are mixed, and the data of the block is erased to make the available free sector.
Due to the above data movement, the sector number and flash memory 5
The sector table 41 is updated because the correspondence with the memory address of is changed.

When a command for resetting the memory card 1 is supplied, or the memory card 1
When the power is turned off, that is, when the power supply to the PSRAM 4 is stopped, the data held in the PSRAM 4 is transferred to and saved in the flash memory 5. FIG. 3 is a flowchart showing a procedure of processing for reflecting the contents of the sector table 41 in the sector management data 51. A process of comparing the contents of the sector management data 51 with the contents of the sector table 41 corresponding thereto in block units and rewriting the data of the block in which a mismatch is detected with the contents of the corresponding sector table 41 will be described with reference to FIG. To do.

When a command for resetting is supplied, the microcomputer 3 sets the value of the start address of the sector management data 51 of the flash memory 5 in a work address pointer Ai (not shown) incorporated therein (step S1). The data held at the address indicated by the work address pointer Ai and the data of the sector table 41 corresponding thereto are respectively acquired (steps S2 and S3), and the acquired data of the flash memory 5 and the corresponding data are acquired. The data in the sector table 41 is compared (step S4). If they match, the microcomputer 3 displays the sector table 41.
The value of the work address pointer Ai is compared with the final address of the valid data of the block including the address indicated by the work address pointer Ai (step S5). The work address pointer Ai
If the value of and the last address of the above block match,
It is determined that the contents of the block all match. Therefore, the contents of the block are not rewritten. If there is an uncompared block in the flash memory 5 storing the sector management data 51 (step S9), the start address of the uncompared block is set in the work address pointer Ai (step S10).

When the value of the work address pointer Ai is not the final address of the block, the microcomputer 3 acquires the uncompared data stored in the block, and therefore the value of the work address pointer Ai is set to the next value. (Step S6).

If the data in the flash memory 5 indicated by the work address pointer Ai does not match the corresponding data in the sector table 41,
The microcomputer 3 collectively erases the data of the block in which the mismatch is detected (step S7), transfers the data of the sector table 41 corresponding to the block and writes the data in the flash memory 5 (step S8), and the sector management. The data 51 is updated. If there is an uncompared block that stores the sector management data 51 (step S9), the microcomputer 3 sets the start address of the uncompared block in the work address pointer Ai after the rewriting operation is completed. (Step S10).

The microcomputer 3 repeats the comparison operation until the comparison of all the blocks storing the sector management data 51 and the corresponding sector table 41 is completed (steps S2 to S10).

When the comparison of all the blocks storing the sector management data 51 is completed, a signal not shown is output via the card interface 2 to notify the host CPU 11 that the update of the sector management data 51 is completed. (Step S11).

The memory card 1 is powered off by the host C.
The microcomputer 3 is notified by a signal (not shown) supplied from the PU 11 via the system bus 13. At this time, if there is data held in the write buffer 42, the microcomputer 3 writes the data in the flash memory 5 and updates the sector table 41. After the writing is completed, the microcomputer 3 updates the sector management data 51 in the same procedure as when the reset command is supplied. That is, the value of the start address of the sector management data 51 is set in the work address pointer Ai (step S
1). While advancing the value of the work address pointer Ai, the contents of the sector management data 51 and the contents of the corresponding sector table 41 are compared in block units, and the data of the block in which a mismatch is detected is stored in the corresponding sector table 41. Rewrite by. (Step S2-
S10). When the comparison of all the blocks storing the sector management data 51 and the rewriting of the block in which the mismatch is detected are completed, the host CPU 11 indicates that the update of the sector management data 51 is completed by a signal not shown.
(Step S11).

According to this embodiment, there are the following effects.
Sector management data 51 stored in the flash memory 5
Contents are transferred to the PSRAN 4 to generate the sector table 41, and the sector table 41 is sequentially updated in accordance with changes in the usage status of the sector. When the power supply of the PSRSM4 is stopped, the latest sector usage status held in the sector table 41 is reflected in the sector management data 51. At this time, the data of the sector management data 51 and the corresponding data of the sector table 41 are compared in block units of the flash memory 5, and the data is rewritten only in the unmatched blocks. As a result, unnecessary rewriting of the sector management data 51 in the flash memory 5 can be prevented, and the number of times of rewriting data in the flash memory 5 can be reduced.

By not rewriting the block having the same contents by the comparison operation, the time required for rewriting the sector management data 51 can be shortened. One block shown in this embodiment is 16
A case of a flash memory having a capacity of K bytes will be described as an example. In the flash memory 5, assuming that the data erasing speed is 2 seconds / block and the data writing speed is 10 microseconds / byte, the time required for rewriting data of one block is 2 seconds + (10 microseconds * 16 Kbytes) = 2160 mm. Seconds. On the other hand, the processing speed of the operation of reading and comparing the data in the flash memory 5 and the corresponding data in the PSRAM 4 is 1 microsecond / byte. Therefore 1
The time required to compare the data of a block, that is, 16 Kbytes is 16 milliseconds. As a result, the difference between the time required to rewrite the data and the time required to perform the comparison operation is 2160 ms−16 ms = 2144 ms. As described above, the comparison operation is completed in a time shorter than 2 seconds per block as compared with the data rewriting. Therefore, even if the comparison operation takes some time, if the contents of the sector management data 51 and the contents of the sector table 41 match in block units, the contents of the sector management data 51 are unconditionally rewritten. The processing time can be shortened compared to the case of That is, by preventing unnecessary rewriting of the sector management data 51 by the comparison operation, the processing time when the power of the memory card 1 is stopped can be shortened.

The comparison operation can be controlled by the microcomputer 3 by adding the function of the comparison operation to the operation program of the microcomputer 3. Thereby, the comparison operation can be performed without adding a circuit to the memory card 1.

The write buffer 4 is added to the PSRAM 4.
2 is provided to temporarily hold the data to be written in the flash memory 5. This eliminates the need to wait for the end of the data erasing of the flash memory 5 and improves the processing capacity of the file memory system using the memory card 1.

Further, the memory card 1 has the same capacity as the sector used in a hard disk device (hereinafter also simply referred to as HDD) or a flexible disk device (hereinafter simply referred to as FDD), for example, 512 bytes. Can be connected to a disk interface (not shown) of the host system 10. Accordingly, the memory card 1 can be used as an auxiliary storage device of the host system 10 instead of the magnetic storage device such as the FDD or HDD. Further, since the memory card 1 does not need to rotate the magnetic disk, it consumes less power than the magnetic storage device, and is advantageous in downsizing and weight saving. Therefore, by using the memory card 1, it is possible to reduce the size and weight of the host system 10 and save power.

Although the invention made by the present inventor has been specifically described based on the embodiments, the present invention is not limited thereto and needless to say, various modifications can be made without departing from the scope of the invention. Yes.

For example, the configuration of the memory card according to the present invention is not limited to this embodiment. For example, a volatile semiconductor memory device other than the pseudo static random access memory such as the dynamic random access memory can be used. It is also possible to generate a write buffer in the card interface means.

The control means is not limited to this embodiment. For example, a comparator may be provided in the card interface, and the control means may be configured by the comparator, a register for taking in the data of the sector management data, and a register for taking in the data of the sector table.
That is, the sector management data to be compared and the sector table may be fetched into the respective registers, and the data fetched in the register by the comparator may be compared.

Further, the types of commands and signals for instructing the operation of the memory card are not limited to those in this embodiment.

In the above description, the case where the invention made by the present inventor is mainly applied to a memory card used as an auxiliary storage device of a computer, which is a field of application of the background, has been described, but the present invention is limited thereto. However, the technique is effective when applied to a file memory system using a non-volatile semiconductor memory device capable of electrically rewriting data at least in block units.

[0046]

The effects obtained by the typical ones of the inventions disclosed in the present application will be briefly described as follows.

That is, the utilization status of each sector, which is a unit for storing a file, is held in a sector table generated in the volatile semiconductor memory device, and the nonvolatile semiconductor memory is used when the power supply to the volatile semiconductor memory device is stopped. By rewriting the contents of the sector management data stored in the storage device, in the file memory system intended to reduce the number of times of rewriting to the nonvolatile semiconductor memory device, in the case of rewriting the sector management data, the sector management data, The contents of the sector table are compared with each other, and the sector management data is rewritten with the contents of the sector table only in the block in which a mismatch is detected. This prevents unnecessary rewriting of the sector management data, and the sector management data can be updated without unnecessarily increasing the number of times of rewriting of the nonvolatile semiconductor memory device.

Further, since the wasteful data rewriting is prevented, the data rewriting time of the nonvolatile semiconductor memory device for reflecting the contents of the sector table in the sector management data when the power supply is stopped can be shortened. You can

The data of the block which stores the sector management data is rewritten to the data of the corresponding sector table after the comparison operation for the block is stopped when the mismatch is detected. As a result, the time for performing the comparison operation until the final data of the block is detected after the above mismatch is detected is omitted. Therefore, the time required for rewriting the sector management data stored in the nonvolatile semiconductor memory device is further shortened.

For a nonvolatile semiconductor memory device such as a flash memory in which a memory cell is electrically stressed by rewriting the stored data, reducing the number of times of rewriting the stored data suppresses the deterioration of the memory cell. it can. Therefore, it is possible to extend the life of the memory card equipped with the nonvolatile semiconductor memory device and reduce the use cost of the file memory system.

[Brief description of drawings]

FIG. 1 is a block diagram of a memory card according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an example of storage areas of a flash memory and a PSRAM of the memory card shown in FIG.

3 is a flowchart of an example of an operation of comparing sector management data and a sector table in the memory card shown in FIG.

[Explanation of symbols]

 1 Memory Card 2 Card Interface 3 Microcomputer 4 PSRAM 5 Flash Memory 11 Host CPU 13 System Bus 41 Sector Table 42 Write Buffer 51 Sector Management Data

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiko Saie 5-20-1 Kamimizuhoncho, Kodaira-shi, Tokyo Hiratsuko ELS Engineering Co., Ltd. (72) Inventor Takashi Kikuchi Kodaira, Tokyo 5-20-1 Jitsumizu Honcho, Ichi, Japan, within Hitate Super L.S.I. Engineering Co., Ltd. (72) Inventor Hiroshi Fukuda 5-20-1, Kamimizuhoncho, Kodaira, Tokyo Metropolitan Government I Engineering Co., Ltd. (72) Inventor Takeshi Suzuki 5-20-1 Kamimizuhonmachi, Kodaira-shi, Tokyo Hiratsuru SLS Engineering Co., Ltd. (72) Inventor Shigeru Kadowaki Kodaira, Tokyo 5-20-1 Jousuihonmachi Hitate Super LSI Engineering Co., Ltd. (72) Inventor Kyoo Okubo Higashi 5-20-1 Kamimizuhoncho, Kodaira-shi, Tokyo Within Hitsudori SLS Engineering Co., Ltd. (72) Inventor Masamichi Kishi 5-20-1 Kamimizuhoncho, Kodaira-shi, Tokyo SII Engineering Co., Ltd. (72) Inventor Kunihiro Katayama 1099, Ozenji, Aso-ku, Kawasaki-shi, Kanagawa Hitachi, Ltd. System Development Laboratory Hitachi, Ltd. Office Systems Division

Claims (3)

[Claims] 1. A file memory system for storing file data in sector units, wherein data can be electrically erased in block units having a storage capacity of a plurality of sectors, and the utilization status of each sector is A nonvolatile semiconductor memory device having a storage area for the sector management data shown, and storage of a sector table in which the sector management data transferred from the nonvolatile semiconductor memory device is initialized and the contents are updated according to a file operation. A volatile semiconductor memory device having an area, and the contents of the sector management data held by the nonvolatile semiconductor memory device when the power supply to the volatile semiconductor memory device is stopped The above sector that is compared with the contents and corresponds only to the storage area of the block in which a mismatch is detected A file memory system comprising: a control unit that rewrites the contents of a table. 2. The control means, when the non-coincidence is detected, interrupts the comparison operation for the non-coincidence block to perform rewriting, and then stores the sector management data in another block not yet compared. 3. The file memory system according to claim 1, wherein the operation shifts to a comparison operation between the contents of the sector table and the contents of the sector table corresponding thereto. 3. A card interface means for exchanging information with the outside is further provided, and the non-volatile semiconductor memory device, the volatile semiconductor memory device, and the control means are connected to the card interface means, respectively. 3. The file memory system according to claim 1, wherein the entire file memory system is mounted on a card substrate to form a memory card.