JPH05204561A - Semiconductor disk having flash memory as storage medium - Google Patents

Abstract

(57) [Summary] [Structure] In a semiconductor disk using a flash memory as a storage medium for rewriting in block units, at least a data memory for storing file data, and a substitute for a block in which an error occurs in the data memory A semiconductor disk having a memory, an error memory for storing error information of the data memory, a data memory, an alternative memory, and a memory controller for reading, writing, and erasing the error memory. [Effect] Since the write error of the flash memory can be relieved, the life of the semiconductor disk can be extended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor disk having a flash memory as a storage medium, and more particularly to a method for extending the life.

[0002]

2. Description of the Related Art Conventionally, D has been used as a medium for semiconductor disks.
RAM and SRAM are used. DRAM or S
A semiconductor disk using a RAM is faster than a magnetic disk and is easy to miniaturize. However,
Both DRAM and SRAM are volatile memories that require battery backup, and DRAM requires complicated memory control because it requires memory refresh.
M has low power consumption but is expensive, so it is not popular. However, when a flash memory is used as a storage medium for a semiconductor disk, it is a non-volatile memory, so battery backup is unnecessary, and because the structure is simple, the chip area can be smaller than that of a DRAM, making it suitable for mass production and cheaper. It is expected as a storage medium.

[0003]

The flash memory can read data in small data units such as byte and word units like the DRAM and SRAM, but the writing is limited in the number of rewrites. The unit is a block unit such as 512 bytes, and the number of rewrites is reduced.

Further, it is necessary to erase data before rewriting due to its structure. Therefore, some flash memories have a command processing function such as erasing.

However, when the flash memory is used as a storage medium for a semiconductor disk, the most problem is the limitation on the number of rewrites. For example, since an area such as a directory or a FAT area has a larger number of rewriting times than other areas, only a specific block of the flash memory used for the directory or FAT area may exceed the rewriting frequency limit of the flash memory. high. Therefore, even if only a specific block becomes abnormal, all the semiconductor disks cannot be used and reliability is low.

An object of the present invention is to extend the life of a semiconductor disk using a flash memory as a storage medium.

[0007]

In order to achieve the above object, in a semiconductor disk using a flash memory as a storage medium, the flash memory has an error in the data memory area for storing data and the data memory. An alternative memory area for replacing the area, and an error memory area having, as error information, the address of the alternative memory of the data memory in which the error occurred, the data memory area, the alternative memory area, and the error memory area It has a memory controller for reading and writing data to and from.

[0008]

In the semiconductor disk using the flash memory as a storage medium, the memory controller reads the error information in the error memory area. Next, according to the error information, when the data memory area is normal, it is read or written in the data memory area, and when abnormal, it is read or written in the alternative memory area. When an error occurs at the time of writing, the free area of the alternative memory area is searched, the data is written to the free area, and the error information of the memory area where the error matches is updated.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a block diagram of an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a semiconductor disk, which is connected to the host bus 3 of the host system 2. The semiconductor disk 1 comprises a microcomputer 4, a memory controller 5, a buffer memory 6, an error memory 7 and a data memory 8. Buffer memory 6
Is the data to be written in the data memory 8 and the error memory 7,
Alternatively, an easily readable / writable SRAM is used as a memory for temporarily storing the read data. Data memory 8 is 2
I have 16 Mbytes of flash memory. Therefore, the storage capacity of the semiconductor disk is 32 Mbytes.
The error memory 7 is a 512 kbyte flash memory and stores the error information of the data memory 8 and the data of the block of the data memory 8 in which the error has occurred. Both the data memory 8 and the error memory 7 are written in blocks of 512 bytes. Microcomputer 4
Receives an instruction from the host bus 3 and controls the memory controller 5 according to this instruction. The memory controller 5 reads and writes the buffer memory 6, the error memory 7, and the data memory 8 at the address 9, data 10,
Control is performed using the control signal 11. Also, the error memory 7
Since the data memory 8 also needs to be erased, this is also controlled.

FIG. 2 shows an example of a memory map of the error memory 7. The areas are the error information area 71 and the usage information area 7.
2 and the alternative memory area 73. It is necessary to divide these areas according to the write block boundaries. The error information area 71 is an area for storing error information corresponding to each block of the data memory 8. The error information is represented by FFFFh when there is no error in the block,
In the case of an error, it shows the block number of the alternative memory to substitute. The usage information area 72 is an area for storing usage information corresponding to each alternative block in the alternative memory area 73. One bit of usage information is assigned to each alternative block. It is represented by 1 when the alternative block is used as an alternative, and by 0 when it is not used. A free block in the alternative memory area 73 can be found by searching for a 0 bit in this area. The alternative memory area 73 is the data memory 8
In the area which replaces the block in which the error occurs, the block is composed of 512-byte blocks similar to the data memory 8, and the replacement block number is sequentially assigned to each block from the address 20000h.

Next, the operation of the semiconductor disk 1 of this example will be described. First, it is assumed that a file data read command is received from the host bus 3. In this case, first, the microcomputer 4 processes this command, but the control contents also differ depending on how the command is given. For example, when the allocation information of the file data to be read is given by a sector number or a track number as in the magnetic disk, it is necessary to convert this to the physical address of the data memory 8. In this example, for simplicity, the allocation information from the host bus 3 is the block number of the data memory 8. The block number corresponds to the upper bits of the physical address. FIG. 3 shows a processing procedure when the microcomputer 4 reads.
First, at 100, the error information of the block number given from the host bus 3 is read from the error information area 71 of the error memory 7. For example, when reading the block 1, the address 00002h of the error memory 7 and the block 2 are 00
Read the error information at address 004h. Next, it is checked from the error information read at 101 whether the block is normal. In the case of reading block 1, it can be seen that the error information is FFFFh, so that block 1 is normal, and in the case of block 2, the error information is 0000h, which is abnormal. If it is normal as in block 1, data of 512 bytes is read from block 1 of the data memory 8 at 102 and transferred to the host bus 3. In the case of an abnormal block such as the block 2, the data of 512 bytes is read from the alternative block 0 of the alternative memory area 73 indicated by the error information 0000h in 103 and transferred to the host bus 3. Here, the reading of the error memory 7 and the data memory 8 and the data transfer to the host bus 3 are performed by the memory controller 5 under the control of the microcomputer. As described above, in the operation of reading the file data, the error information is read before reading the target block to check whether the target block is normal. The block of the data memory 8 when normal, the alternative memory area 73 when abnormal
Read the alternative block of.

Next, a case where a file data write command is received from the host bus 3 will be described. FIG. 4 shows a processing procedure of the microcomputer 4 at the time of writing. First, the microcomputer 4 transfers the file data given from the host bus 3 to the buffer memory 6 at 200. This is done in order to reduce the waiting time of the host system 2 because writing to the flash memory takes longer than reading. Next, the error information of the block number to be written in 201 is displayed in the error information area 7 of the error memory 7.
Read from 1. The error information is checked at 202 as in the case of reading. For example, since the error information of block 1 is FFFFh, it is a normal block, and the error information of block 2 is 0000h, it is an abnormal block. When writing the file data to the block 1, since it is writing to the normal block, the data of the block 1 of the data memory 8 is erased at 203, and the file data stored in the buffer memory 6 at 204 is written to the block 1 of the data memory 8. Write. In the case of writing to the block 2, since the block 2 of the data memory 8 is abnormal, the data of the alternative block 0 of the alternative memory area 73 indicated by the error information value 0000h is erased at 205,
At 206, the file data in the buffer memory 6 is written to the alternative block 0. Next, at 207, it is checked whether writing to the data memory 8 or the error memory 7 has been normally performed. The writing error occurs in the flash memory when the writing frequently occurs only in a specific block and the number of rewriting times of the flash memory is exceeded. If the data is normally written in the check in 207, the processing of the file data write command from the host bus 3 ends. On the other hand, if the writing is not successful in this check, the error information is updated and the alternative block is allocated by the procedure of 208.

FIG. 5 shows an error processing procedure. First, 2
At 09, the usage information in the usage information area 72 of the error memory 7 is read, and at 210, an unused alternative block is searched from the usage information. In FIG. 2, it can be seen that the 0th to 3rd bits are 1 and are in use, and the 4th bit, that is, the alternative block 4 is unused. Therefore, the replacement block 4 replaces the block in which the write error occurs. Therefore, in 211, the data of the alternative block 4 is erased,
At 212, the file data in the buffer memory 6 is written in the alternative block 4. Next, in 213, the block storing the error information of the block in which the write error has occurred in the error information area 71 is set to the buffer memory 6
Transfer to. Then, at 214, the buffer memory 6
The error information stored in is rewritten with new error information. For example, in the case of a block 1 write error, 000
The FFFFh at the address 02h is rewritten to the block number 0004h of the alternative block 4. Then, in 215, the data of the block that needs to be rewritten in the error information area 71 is erased, and in 216, the data of the buffer memory 6 is written in the original block of the error information area 71. Similarly, in 217, the block of the usage information area 72 is transferred to the buffer memory 6, and in 218, the bit of the alternative block newly used as an alternative this time is rewritten to 1.
Then, after erasing the data in the block of the usage information area 72 in 219, the data of the buffer memory 6 is written in the block of the usage information area 72 in 220. By the above error processing procedure, the error block is replaced with the alternative block and the error information is updated.

Further, in this example, only the writing check is performed in 207, but it may be added in the process subsequent to the erasing in 203 and 205 whether or not the erasing is normally performed. In this case also, the error processing of 208 is performed.

In this example, the error memory 7 is provided with the alternative memory area 73 and the error information area 71, but it may be a separate memory chip. On the contrary, an error information area and an alternative memory area may be provided in the data memory 8. A configuration diagram in this case is shown in FIG. Unlike FIG. 1, the error memory 7 is not necessary in FIG. 6, so that the number of chips can be reduced.

FIG. 7 shows an example of a memory map of the data memory 8 of the embodiment shown in FIG. As shown in FIG. 7, the data memory 8 is divided into four areas of an initialization information area 81, an error information area 82, an alternative memory area 83, and a data area 84.
The alternative memory area 83 is an area that replaces an error block of the data area 84, and the error information area 82 is address information of each block of the data area 84, or the address of the alternative block when the block of the data area 82 is in error. Store information. Here, the address information represents the upper bit of the physical address of the data memory 8 or the physical block number. The initialization information area 81 is the alternative memory area 8
3 and the start address and capacity of the error information area 82 and the data area 84 are stored, and the address information of the unused alternative memory is also stored. The user can freely set the size of the alternative memory area 83 by setting the initialization information area 81 when the semiconductor disk is initialized.

Next, the operation of this example will be described. First,
FIG. 8 shows a processing procedure of the microcomputer 4 when receiving a read command from the host bus 3. The block number of the data area 84 is given from the host bus 3. At first,
The microcomputer 4 reads error information from the error information area 82 at 300. The address of the error information is calculated and obtained from the error information start address of the initialization information area 81 and the block number given from the host bus 3. For example, if the block number to be read is 0, the error information address is the error information start address 0001 multiplied by 512, which is 20.
This is the first address of 0h. Then at 301 at 30
The physical block corresponding to the error information read at 0 is read. When the block number to be read is 0, the error information is 200h, so the data area 8 is obtained by multiplying 200h by 512.
Read from address 4 at 4000h. If the block number to be read is 2, the error information is 100h, so the data is read from the address 2000h in the alternative memory area 83. As described above, in this example, since the error information directly represents the physical address of the data memory, there is an advantage that the error check processing 101 is not required unlike the embodiment of FIG.

Next, the case where a write command is received from the host bus 3 will be described. FIG. 9 shows a processing procedure at the time of writing. First, at 400, the data given from the host bus 3 is written in the buffer memory 6. Next, the error information of the block to be written is read from the error information area 82 as in the case of reading. Then, the physical address of the block to be written is calculated from the error information read in 402, and the data of the block at that physical address is erased. Then, in 403, the write data stored in the buffer memory 6 is written in the block of the data memory 8 represented by the physical address calculated in 402. Then write 4
At 04, it is checked whether the writing of 403 is normally performed. If the writing is normal, the writing process ends, but if it is not normal, an error process 405 is performed. In the error processing 405, the alternative block of the block in which the write error occurs is secured, the write data is transferred to the alternative block, and the error information and the initialization information are updated. First, in 406, an alternative memory unused address is read from the initialization information area 81. The value of the alternative memory unused address represents the address of the new alternative block. Next, at 407, the data in the block represented by the alternative memory unused address is erased. 104h in the example of FIG.
The block at address 20800h which is multiplied by 512 is deleted. Next, at 408, the write data in the buffer memory 6 is written to the block at address 208h. Then 409
The data of the block of the error information in which the write error occurs in (1) is read from the error information area 82 and transferred to the buffer memory 6. The transferred error information is updated to new error information at 410. For updating, for example, in the case of a write error to the block 0, the error information 200h of the block 0 is added to the address information 104 of the new alternative block
Rewrite to h. Next, in 411, the data in the block of the error information area 82 to be rewritten is erased and 412
At, the updated error information in the buffer memory 6 is written into the block in which the error information area 82 is rewritten.
Next, in order to update the alternative block unused address of the initialization information area 81, first, at 413, the data of the initialization information area 81 is transferred to the buffer memory 6. Then, in the initialization information transferred in 414, 1 is added to the value of the alternative memory unused address. This value becomes the address information of the new alternative block when the write error occurs next time. Next, at 415, the initialization information area 8
1 data is erased, and the buffer memory 6 at 416
The updated initialization information of the above is written in the initialization information area 81. Writing and error processing are performed in the above procedure.

Further, in the present example, the number of the alternative memory area 83 and the data area 84 is only one each, but by adding other address information and capacity to the initialization information area, a plurality of alternative memory areas 83 and data areas 84 can be obtained. The area 84 may be provided.

As described above, in the semiconductor disk using the flash memory as a storage medium, the error due to the limitation of the number of times of rewriting of the flash memory can be relieved, so that the life of the semiconductor disk can be extended.

Next, the alternative memory areas 73 and 83 and the error information areas 71 and 82 in the embodiments of FIGS.
A method of determining the capacity of will be described.

First, the capacities of the alternative memory areas 73 and 83 depend on how many blocks of the data memory 8 are used as the areas where the host system 2 rewrites most frequently, for example, FAT and directory areas. In this example, of the 32 MB of data memory 8, 128 kB is used as the FAT and the directory area. In this case, the alternative memory areas 73 and 83 have three times 128 kB,
If the capacity of 384 kB is taken, even if the FAT and the directory area are all in error, replacement is possible three times, so the life of the semiconductor disk 1 is quadrupled.

Therefore, when it is desired to increase the life of the silicon disk 1 by n times, the alternative memory areas 73, 83 have a capacity of n-1 times the capacity of the area of the data memory 8 in which data is frequently rewritten. In the case of the embodiment shown in FIG. 7, since 128 kB is used as the alternative memory area 83, the life is doubled. In general, rewriting is not frequently performed in all of the FAT and the directory area, so it is expected that the life will be further extended.
Consider it as a guideline for the capacity of 83.

Next, the capacities of the error information areas 71 and 82 will be described. Alternate memory area 7 in the case of the embodiment of FIG.
Areas for storing the respective block numbers of 3 are required for the number of blocks of the data memory 8. That is, in this example, the alternative memory area 73 has 768 blocks (384 kB), and the data memory 8 has 64 k blocks (32 MB).
It is necessary to have at least 80 kB, which is a capacity for storing 64 k pieces of 10-bit address information indicating

In the case of the embodiment of FIG. 7, the error information area 82
Requires an area for storing the block number of the alternative memory area 83 or the data area 84 for the number of blocks of the data area 84. In this example, since 256 blocks are given to the alternative memory area 83 and 65024 blocks are given to the data area 84, the 16-bit information indicating the block number is 650.
A capacity for storing 24 pieces is required.

Usage information area 72 and initialization information area 8
1 allocates the remaining capacity.

When each of these areas is divided, it is convenient to divide each area in units of blocks which are rewriting units of the flash memory.

As described above, according to the present invention, the life of the semiconductor disk 1 is extended by using the capacity of 2% or less with respect to the total capacity of the flash memory for the error information areas 71 and 82 and the alternative memory areas 73 and 83. It can be doubled or more. Further, when it is desired to further extend the life, the capacity of the alternative memory areas 73 and 83 is increased, and the life is extended accordingly.

Next, the interface between the host system 2 and the semiconductor disk 1 will be supplementarily described. The host system 2 is an information processing device such as a personal computer or a word processor, and the host bus 3 is a bus to which the host system 2 usually connects a file device such as a magnetic disk. Generally, the host bus 3 connecting the magnetic disk has a SCSI or IDE interface. Similarly to the magnetic disk, the semiconductor disk 1 of the present invention can be easily transferred from the magnetic disk to the semiconductor disk 1 when connected to the host bus 3 such as SCSI or IDE interface.

In order to connect the semiconductor disk 1 to the SCSI or IDE interface, it is necessary to make it the same as the interface of the magnetic disk. For that purpose, first, it is necessary to make the block size of the flash memory correspond to the sector of the magnetic disk. In this embodiment, the block size is 512 bytes, but this is adapted to the sector size of the magnetic disk. If the block size is smaller than the sector size of the magnetic disk, there is no problem if a plurality of blocks are used as one sector, but if the block size is large, it is necessary to divide the block into several sector sizes for use. In addition, a flash memory may be logically assigned to a track or a head corresponding to a track or a head of a magnetic disk. Further, the interfaces such as control registers and interrupts are made the same, and the semiconductor disk 1 is controlled by an input / output command of the magnetic disk given from the host bus 3. However, it is necessary to replace the command peculiar to the magnetic disk, for example, the process of controlling the motor with another process.

Table 1 below shows an example of an instruction to the magnetic disk, processing of the magnetic disk for the instruction, and processing of the semiconductor disk 1 when the instruction of the magnetic disk is applied to the semiconductor disk 1 as it is. is there.

[0032]

[Table 1]

This is an example of an IDE interface. In Table 1, No. 1 and No. Although 6 is a head movement command, this process is not performed because the semiconductor disk 1 has no head. Further, since the flash memory has a significantly lower error rate than the magnetic disk, it is not necessary to provide an ECC. Therefore, Read Verify S
The actor instruction does not perform any processing. Other commands are listed in Table 1.
As shown in.

Even if the process in Table 1 is not performed, if an interrupt or the like is generated in the magnetic disk, the semiconductor disk 1 similarly generates an interrupt. That is, the interface is taken so that the magnetic disk and the semiconductor disk 1 are not distinguished from the viewpoint of the host bus 3.

By making the interface of the magnetic disk the same as the interface of the semiconductor disk 1 as described above, replacement of the magnetic disk with the semiconductor disk 1 becomes easy.

ID for SCSI interface
Similar to the E interface, if the same interface as the magnetic disk is used, replacement can be easily performed. But,
Since the SCSI interface can be connected to other devices such as a magneto-optical disk in addition to the magnetic disk, it has a command system specific to the file device, and it is wasteful to form a dedicated command system for the semiconductor disk 1 as well. It can be speeded up. However, basically, it has the same command system as the magnetic disk and has no motor control command. In this case, the block size of the flash memory may be any number of bytes, and one block of the flash memory may be processed as one sector. The host system 2 may perform the processing of the microcomputer 4 shown in the embodiments of FIGS. 1 and 6 and the processing of the flowcharts of FIGS. 3, 4, 5, 8, and 9.

Although JEIDA and PCMCIA are standard IC card interface specifications, the semiconductor disk 1 of the present invention may be converted into an IC card, and the semiconductor file 1 may be constructed by making the interface compliant with JEIDA or PCMCIA. In this case, the semiconductor disk 1 is treated as an IO device.

Semiconductor disk 1 in comparison with magnetic disk
The advantage of is that the processing of the semiconductor disk 1 requires less processing than the magnetic disk as shown in Table 1, so that the speed can be increased, and the power consumption is low because there is no mechanical part such as a motor. Further, it has shock resistance against vibration and the like, and since it has high reliability, ECC is not required.

The flash memory is used as a storage medium because it is non-volatile, so that it retains data even when the power is off and does not require battery backup like SRAM and DRAM, and its structure is simpler than that of EEPROM. This is because there is an advantage that the capacity can be easily increased and the mass production can be performed at a low cost.

Further, in the present invention, the flash memory is divided into a plurality of areas, a plurality of data memory areas which store data and are provided corresponding to the above areas, and a data memory in which an error has occurred. A plurality of alternative memory areas that are provided to correspond to the above areas by substituting the areas, a plurality of error memory areas that are provided to correspond to the above areas that store error information of the data memory area, and It may have an initialization information area for storing the start address and the capacity. According to this, when a flash memory is newly added to expand the storage capacity, if three kinds of memory areas are newly added, the stored contents of the error memory area and the data memory area are not changed. , Can be expanded. Information of the expanded memory may be stored in the initialization information area.

Further, in the present invention, the error memory area may also have error information of the alternative memory area where the error has occurred. By doing so, not only the error in the data memory area but also the error can be relieved even when an error occurs in the alternative memory area where the data memory area is once replaced. The alternative method may be the same as when an error occurs in the data memory area. By substituting the alternative memory area, the life can be extended.

Further, in the present invention, the capacity of the alternative memory area may be a predetermined partial area of the data memory area. As a method of selecting an area, an area in which rewriting is most frequently performed may be selected.
Then, if there are few alternative areas, the life can be significantly extended.

[0043]

According to the present invention, in a semiconductor disk using a flash memory as a storage medium, the life of the semiconductor disk can be extended.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a semiconductor disk and a host system according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a memory map of an error memory 7.

[Fig. 3] Flow chart of the microcomputer 4 at the time of reading

FIG. 4 is a flowchart of the microcomputer 4 at the time of writing.

[Fig. 5] Flowchart of the microcomputer 4 when an error occurs

FIG. 6 is a configuration diagram of a semiconductor disk and a host system according to another embodiment of the present invention.

FIG. 7 is an explanatory diagram of a memory map of a data memory 8 according to another embodiment of the present invention.

FIG. 8 is a flowchart of the microcomputer 4 of another embodiment at the time of reading.

FIG. 9 is a flowchart of the microcomputer 4 of another embodiment at the time of writing.

[Explanation of symbols]

 1. ． ． Semiconductor disk 2. ． ． Host system 3. ． ． Host bus 4. ． ． Microcomputer 5. ． ． Memory controller 6. ． ． Buffer memory 7. ． ． Error memory 8. ． ． Data memory 71. ． ． Error information area 72. ． ． Usage information area 73. ． ． Alternate memory area 81. ． ． Initialization information area 82. ． ． Error information area 83. ． ． Alternate memory area 84. ． ． Data area

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshihiro Hayashi 7-1, 1-1 Higashi Narashino, Narashino City, Chiba Prefecture Office Systems Design and Development Center, Hitachi Ltd. (72) Takashi Tsunehiro Yoshida Town, Totsuka Ward, Yokohama City, Kanagawa Prefecture 292 Incorporated Hitachi, Ltd. Microelectronics Equipment Development Laboratory (72) Inventor Tsuyoshi Furuno 4-6, Kanda Surugadai, Chiyoda-ku, Tokyo Inside Hitachi, Ltd.

Claims (12)

[Claims] 1. A semiconductor disk using a flash memory as a storage medium, wherein the flash memory has a data memory area for storing data, an alternative memory area for substituting an error area of the data memory, and the data memory. An error area having the address of the alternative memory of the errored data memory as error information, and a memory controller for reading and writing to the data memory area, alternative memory area, and error memory area. Semiconductor disk characterized by. 2. The semiconductor disk according to claim 1, wherein, when an error occurs in the alternative memory area, the error memory area has an address of the alternative memory area where the error has occurred as error information. Semiconductor disk. 3. The semiconductor disk according to claim 1 or 2, wherein the error memory area has a usage status of an alternative memory area as error information. 4. A method of reading and writing data using the semiconductor disk according to claim 1, 2 or 3, wherein the error information in the error memory area is read, and the data memory area is normally detected by the error information. If an error occurs during writing, read or write to the data memory area, or to the alternate memory if an error occurs.If an error occurs during writing, search for an empty area in the alternate memory area, write the data to the empty area, and A method of reading and writing, characterized by updating error information in an error area of a memory having a certain error. 5. A semiconductor disk having a flash memory as a storage medium, comprising a memory controller for reading and writing to the flash memory, wherein the flash memory has a data memory area for storing data and an error. Semiconductor memory having an alternative memory area for replacing the data memory area, an error memory area for storing error information of the data memory area, and an initialization information area for storing the start address and capacity of each area. .. 6. A semiconductor disk using a flash memory as a storage medium, comprising a memory controller for reading and writing to the flash memory, wherein the flash memory is divided into a plurality of areas for storing data. The data memory areas provided corresponding to the above areas and the data memory areas in error are replaced, and the plurality of alternative memory areas provided corresponding to the above areas and the data are A semiconductor, which stores error information of a memory area and has a plurality of error memory areas provided corresponding to the above areas, and an initialization information area for storing a start address and a capacity of each area. disk. 7. The semiconductor disk according to claim 5, wherein the capacities of the data memory area and the alternative memory area are variable. 8. The semiconductor disk according to claim 1, 2, 3, 4, 5, 6 or 7, wherein the error memory area also has error information of an alternative memory area where an error has occurred. Semiconductor disk. 9. A semiconductor disk using a flash memory as a storage medium, which has the same electrical interface as a magnetic disk and receives the same electrical signal as an electrical signal for operating the magnetic disk. A semiconductor disk. 10. A semiconductor disk using a flash memory as a storage medium according to claim 9, and receiving means for receiving a command for a magnetic disk from the outside, and converting the received command into a command for the semiconductor disk. A semiconductor disk having a converting means. 11. In a semiconductor disk using a flash memory as a storage medium, a block size, which is a rewriting unit of the flash memory, and a sector size, which is a processing unit of a file of a host system connected to the semiconductor disk, have the same size. A semiconductor disk characterized in that. 12. The semiconductor disk according to claim 1, 2, 3, 4, 5, 6, 7 or 8, wherein the capacity of the alternative memory area is a predetermined partial area of the data memory area. A semiconductor disk characterized in that.