JP3769395B2 - External storage device using non-volatile memory - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an external storage device of a computer using, for example, a flash memory as a nonvolatile memory.
[0002]
[Prior art]
As an external storage device of a computer, there is a magnetic disk drive (hard disk drive, hereinafter referred to as H / D). Although this H / D has a large capacity but uses mechanical parts, it has a drawback that it is vulnerable to shock and vibration. In order to solve this drawback, an external storage device using a flash memory as a storage medium has been developed.
[0003]
The external storage device is accessed for reading and writing in units of sectors, and 512 bytes is often used as the sector size.
[0004]
The flash memory needs to be erased before writing because of the structure of the device. In addition, the flash memory has a fast read access time but a long erase time and write time. Furthermore, flash memory currently has 10 write cycles. ^Five There is a limit of times. For this reason, if a certain location in the flash memory reaches the above-mentioned limit on the number of writes due to the concentration of writing, it can be used as an external storage device even if other areas of the flash memory can be used. It becomes impossible.
[0005]
Therefore, conventionally, the flash memory is divided into a plurality of physical sectors for storing sector-size data, and the write data from the host computer is controlled so as to be written in the physical sectors with a small number of writes. Concentration of writing to a certain location is avoided, the life of the flash memory is extended, and the life of the external storage device using the flash memory is extended.
[0006]
[Problems to be solved by the invention]
By the way, in the conventional technology, the physical sector in the flash memory is divided into a data area for holding write data from the host computer and a management area, and this management area has a logical sector address which is an access address of the host computer. Was stored.
[0007]
When writing data from the host computer, the write data from the host computer is written to the data area of the physical sector of the flash memory, and then the logical sector address, which is the access address of the host computer, is written to the management area of the physical sector.
[0008]
An external storage device using a flash memory is provided with a mapping table for converting a logical sector address, which is an access address from a host computer, into a physical sector address in the flash memory. The mapping table and the pointer are updated each time data is written from a specific host computer in order to avoid repetitive writing of only a specific write area. For this reason, the mapping table and the pointer are created on the RAM.
[0009]
On the other hand, in the field of semiconductors, miniaturization technology is remarkably progressing.
In various memory devices, the progress of this miniaturization technology increases the storage capacity per memory device, but reduces the amount of stored charge due to the reduction in volume occupied by one memory cell and increases the probability of occurrence of micro defects. In addition, the occurrence probability of error bits in data increases due to external factors such as the application of electrical noise accompanying an increase in operation speed.
[0010]
Therefore, in the prior art, a redundancy mechanism capable of error correction represented by ECC (Error Checking and Correcting Feature) for data stored in the flash memory for each sector in order to ensure data reliability. (Hereinafter referred to as ECC) check bits.
[0011]
However, ECC was not used for the mapping table. This is because in order to use ECC for the mapping table, a separate ECC RAM is required for the mapping table, which increases costs, increases size, and increases power demand.
[0012]
For this reason, when an error bit occurs in the RAM storing the mapping table, the conversion from the logical sector address to the physical sector address is erroneously performed, which is different from the data of the logical sector address requested to the host computer. Send data.
[0013]
As described above, the conventional technique has a problem that data in the external storage device using the flash memory is destroyed when an error bit occurs in the RAM storing the mapping table.
[0014]
The object of the present invention is to improve the reliability of the mapping table without requiring a separate ECC RAM for the mapping table, and to ensure data reliability even when an error bit occurs in the RAM storing the mapping table. It is to realize an external storage device using a nonvolatile memory capable of maintaining the performance.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is configured as follows.
(1) In an external storage device using a non-volatile memory, the non-volatile memory is used as a storage medium, the inside of the storage medium is divided into physical sectors, which are units for reading and writing data, and the physical sectors are written data from the host computer. The storage medium is divided into a data area and a management area for storing the logical sector address, and a logical sector address which is an access address of the host computer is stored in the management area, and the logical sector address and data of the logical sector address are stored in the management area The physical sector address correspondence table is at least duplicated and stored in the mapping table. When data is read from the host computer, the physical sector address corresponding to the logical sector address from the host computer is obtained from each of the duplicated mapping tables. Read, read If the two match each other, it is determined that the contents of the mapping table are correct, the data of the physical sector address of the flash memory obtained from the mapping table is sent to the host computer, and read from each of the duplicated mapping tables. If the physical sector address values are different from each other, the physical sector management area of the physical sector address read from each mapping table is accessed, and a physical sector having the same logical sector address as the access address from the host computer is accessed. If it exists, the data stored in this physical sector is sent to the host computer, and the contents of the mapping table are corrected to the same logical sector address as the access address from the host computer.
[0016]
Since the mapping table is at least duplicated, it is possible to determine that an error bit has occurred in the mapping table by comparing the values stored in each of the duplicated mapping tables with each other. If an error bit occurs in the mapping table, the physical sector management area of the physical sector address read from each mapping table is accessed, and a physical sector address having the same logical sector address as the access address from the host computer is accessed. The data stored in the sector is sent to the host computer and the contents of the mapping table are corrected to the same logical sector address as the access address from the host computer. Therefore, an external storage device using a nonvolatile memory that can maintain the reliability of data can be realized.
[0017]
(2) Preferably, in the above (1), when reading data from the host computer to the external storage device, the physical sector address values read from each of the duplicated mapping tables are different from each other and read from each mapping table. If there is no physical sector with the same logical sector address as the access address from the host computer in the management area, the physical address read from each of the duplicated mapping tables When the physical sector management area of the physical sector address with different bit values is accessed and there is a physical sector with the same logical sector address as the access address from the host computer, this physical sector Stored data Modifying the contents of the mapping table and sends to the host computer.
[0018]
Even if the correct physical sector address is not stored in the mapping table, the management area of the physical sector at the physical sector address in which the values of the bits having different values of the physical address read from each mapping table are changed is accessed. Therefore, it is possible to realize an external storage device using a non-volatile memory that can maintain the reliability of data.
(3) Preferably, in the above (2), when reading data from the host computer to the external storage device, the values of the physical sector addresses read from each of the duplicated mapping tables are different from each other. The physical sector of the read physical sector address does not have a physical sector with the same logical sector address as the access address from the host computer in the management area, and the physical address read from each of the duplicated mapping tables If the physical sector of the physical sector address has changed the value of the bit different from each other, and there is no physical sector with the same logical sector address as the access address from the host computer in the management area, each of the above duplicated mapping Read from table Changed physical address values, and the physical sector management area of the changed physical sector address is accessed, and the physical sector having the same logical sector address as the access address from the host computer If it exists, the data stored in this physical sector is sent to the host computer and the contents of the mapping table are corrected.
[0019]
Since the physical address value read from each mapping table changes the value of the same bit, the management area of the physical sector at the changed physical sector address is accessed, further maintaining data reliability. It is possible to realize an external storage device using a nonvolatile memory.
[0020]
(4) Preferably, in the above (1), (2) or (3), the mapping table is multiplexed more than triple.
[0021]
(5) Preferably, in the above (4), the physical sector addresses read from the multiplexed mapping tables are different when the values of the physical sector addresses read from the multiplexed mapping tables are different from each other. When the majority of the values of the physical sector address can be taken, the physical sector data of the physical sector address that becomes a large number is sent to the host computer, and the physical sector address value corresponding to the logical address from the host computer of the mapping table is the physical sector that becomes the majority. Rewrite the address and finish the process.
[0022]
When the majority of physical sector address values read from each mapping table can be taken, reading from the physical sector management area of the address can be omitted, and the access speed of the external storage device using the non-volatile memory to the host computer is increased. It becomes possible to do.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration of an external storage device according to the first embodiment of the present invention. In FIG. 1, reference numeral 100 denotes an external storage device using a flash memory, and this external storage device 100 is connected to a host computer 200.
[0024]
Reference numeral 1 denotes a host computer interface, and reference numeral 2 denotes a flash memory (storage medium) used as a storage medium of the present invention. A RAM 3 stores a mapping table.
[0025]
Reference numeral 4 denotes a control circuit. The control circuit 4 controls the host interface 1, the flash memory 2, and the RAM 3. Further, the control circuit 4 controls the host interface 1 via the host interface bus 5 and the host interface control line 6. The flash memory 2, the memory address bus 7 of the RAM 3, and the memory data bus 8 are controlled by the control circuit 4 via the memory control line 9.
[0026]
FIG. 2 is a block diagram of the flash memory 2 shown in FIG.
In FIG. 2, the inside of the flash memory 2 is divided into physical sectors 20 which are units of data reading / writing. As the data size of the physical sector 20, 512 bytes are often used in one physical sector.
[0027]
FIG. 3 is a configuration diagram of the physical sector 20 shown in FIG.
In FIG. 3, the physical sector 20 includes a data area 21 that stores write data from the host computer 200 and a management area 22 that stores management information of the physical sector 20. The management area 22 stores a logical sector address 23 which is an access address of the host computer 200 for data written in the data area 21.
[0028]
FIG. 4 is a configuration diagram of the RAM 3 that stores a mapping table (a correspondence table of a logical sector address and a physical sector address in a storage medium in which data of the logical sector address is stored). In the present invention, the mapping table may be multiplexed in the RAM 3, and the example of FIG. 4 is a configuration example when the mapping table is duplicated {(address 0 to n), (0 + x to n + x)}.
[0029]
In FIG. 4, the address of the physical sector that stores the data of logical sector address 0 is stored at address 0 and address 0 + x of RAM 3. Similarly, the address of the physical sector storing the data of logical sector address 1 is stored in address 1 and address 1 + x of RAM 3.
[0030]
That is, if a is an arbitrary address number, the address of the physical sector storing the data of the logical sector address a is stored in the address a and the address a + x of the RAM 3.
[0031]
Here, x is the number of logical sectors of the external storage device 100 using the flash memory. The capacity required for the RAM 3 is m × x × b, where m is the multiplicity of the mapping table and b is the number of bytes required to store the physical sector address.
[0032]
Next, a write operation from the host computer 200 to the external storage device 100 using the flash memory 2 will be described with reference to FIGS.
FIG. 5 shows a data write operation to the flash memory 2 when data is written from the host computer 200 to the external storage device 100 using the flash memory 2.
[0033]
First, the host computer 200 sends the address of the sector to be written and the write data to the host interface 1. Next, the control circuit 4 receives the logical sector address to be written, the write data, and the host interface 1 via the host interface bus 5.
[0034]
Then, the control circuit 4 designates the address of the physical sector 20 to which writing to the flash memory 2 is performed via the memory address bus 7, puts the write data and the logical sector address on the memory data bus 8, and the flash memory 2. Write to. At this time, the control circuit 4 selects a physical sector 20 with a small number of rewrites in order to store write data from the host computer 200 by an algorithm.
[0035]
Further, since the flash memory 2 needs to be erased before writing from the structure of the element, if the physical address sector for writing to the flash memory 2 is not erased, before the data is written The deletion is performed. Write data from the host computer 200 is written in the data area 21 of the physical sector 20, and a logical sector address from the host computer 200 is written in the management area 22.
[0036]
FIG. 6 is a diagram illustrating the mapping table update operation of the external storage device 100 using the flash memory 2 after writing to the flash memory 2. In FIG. 6, the control circuit 4 designates an address at which writing to the RAM 3 is performed via the memory address bus 7, places the physical sector address of the flash memory 2 to which writing has been performed on the memory data bus 8, Write.
[0037]
If the logical sector address from the host computer 200 in the operation shown in FIG. 5 is R1, and the physical sector address of the physical sector selected by the control circuit 4 is P1, the structure of the RAM 3 shown in FIG. And R1 + x are written with the physical sector address P1 of the flash memory 2 that has been written.
[0038]
FIGS. 7 to 9 are diagrams showing operations at the time of read access to the external storage device 100 using the flash memory 2 of the host computer 200 when no error bit occurs in the RAM 3 storing the mapping table.
[0039]
In FIG. 7, the host computer 200 sends a logical sector address to be read to the host interface 1. The control circuit 4 receives a logical sector address to be read through the host interface bus 5.
[0040]
In FIG. 8, after that, the control circuit 4 designates an address for storing the physical sector address of the flash memory 2 corresponding to the logical sector address to be read from the host computer 200 of the RAM 3 via the memory address bus 7. The physical sector address is read from the RAM 3 via the memory data bus 8.
[0041]
In the operation shown in FIG. 7, if the logical sector address from the host computer 200 is R2, and the physical sector address P2 of the flash memory 2 in which the data of the logical sector address R2 is stored, the control circuit 4 The physical sector address stored at address R2 is compared with the physical sector address stored at R2 + x. In this case, in the structure of the RAM 3 shown in FIG. 4, the physical sector address P2 is read from the addresses R2 and R2 + x of the RAM 3, and the two coincide with each other.
[0042]
In FIG. 9, when the address of the physical sector 20 storing the logical sector address data from the host computer 200 is obtained from the RAM 3, the control circuit 4 sends the physical sector 20 obtained from the RAM 3 via the memory address bus 7. Is read from the flash memory 2 via the memory data bus 8.
[0043]
Then, the control circuit 4 sends the read data to the host interface 1 via the host interface bus 5 and further sends the read data from the host interface 1 to the host computer 200.
[0044]
If the control circuit 4 determines that the physical sector addresses read from each of the duplicated mapping tables do not match, the physical sector address read from each mapping table during the operations shown in FIGS. An operation of accessing the management area 22 of the physical sector 20 to confirm whether there is a physical sector 20 having the same logical sector address as the access address from the host computer 200 and an operation of correcting the contents of the mapping table are added.
[0045]
This will be described with reference to FIGS.
In FIG. 10, the control circuit 4 designates the address of the physical sector 20 obtained from each mapping table of the RAM 3 by the memory address bus 7, and enters the management area 22 of the physical sector 20 via the memory data bus 8. The stored logical address of the data stored in the data storage area 21 of the physical sector 20 is read out.
[0046]
As shown in FIG. 11, the physical sector addresses stored in the addresses 0 and 0 + x of the RAM 3 and storing the data of the logical sector address 0 are 100000 and 100001, respectively. As in the operation shown in FIG. 10, data in the management area 22 of the physical sector 20 with addresses 100000 and 100001 is read.
[0047]
Then, after reading the logical sector address from the management area 22 of each physical sector 20, the control circuit 4 confirms whether or not they match the logical sector address from the host computer 200.
[0048]
As shown in FIG. 12, if the data in the management area 22 of the physical sector 20 with addresses 100000 and 100001 are respectively 5 and 0, the physical sector 20 with the address 100001 stores data with the logical sector address 0. Therefore, it is determined that the address 100001 is correct.
[0049]
When the physical sector 20 having the same logical sector address as the access address from the host computer 200 exists as in the example shown in FIGS. 11 and 12, the mapping table of the RAM 3 is corrected by the operation shown in FIG. To do.
[0050]
In the example shown in FIGS. 11 and 12, the value of the physical sector address corresponding to the logical sector address 0 stored in the address 0 of the RAM 3 is rewritten from 100000 to 100001 as shown in FIG.
[0051]
When the mapping table is corrected, the data of the physical sector 20 corresponding to the logical sector address from the host computer 200 is sent to the host computer 200 by the operation shown in FIG.
[0052]
In the example shown in FIGS. 11 and 12, since the address of the physical sector 20 storing the data of the logical sector address 0 from the host computer 200 is 100001, it is stored in the data area 21 of the physical sector 20 of the address 100001. The stored data is sent to the host computer 200.
[0053]
When an error bit occurs at address 0 of RAM 3 as in the examples of FIGS. 11 and 12, since there is only one mapping table in the conventional technique, 100000 stored at address 0 of RAM 3 is logical sector. It is regarded as the address of the physical sector storing the data of address 0.
[0054]
Therefore, although the physical sector at the address 100000 stores the data at the logical sector address 5, the external storage device 100 using the flash memory 2 transfers the data stored in the physical sector at the address 100000 to the logical sector. The data is sent to the host computer 200 as the data of the sector with address 0.
As a result, in the conventional technique, if an error bit occurs in the RAM 3, the reliability of data in the external storage device 100 using the flash memory 2 has been impaired.
[0055]
On the other hand, according to the first embodiment of the present invention, the reliability of data in the external storage device 100 using the flash memory 2 can be ensured by the above-described operation even if an error occurs in the RAM 3.
[0056]
In other words, according to the first embodiment of the present invention, the reliability of the mapping table is improved without requiring a separate ECC RAM for the mapping table, and error bits are generated in the RAM storing the mapping table. Even if it occurs, an external storage device using a nonvolatile memory capable of maintaining the reliability of data can be realized.
[0057]
Recently, the capacity of the RAM has increased due to the progress of miniaturization, so that the mapping table can be multiplexed without increasing the number of elements of the RAM, and the external storage device using the flash memory without increasing the cost. The reliability of 100 data can be improved.
[0058]
In the first embodiment of the present invention described above, when an error bit is generated in the RAM 3 and the number of error bits is 1, the flash memory is used as in the example shown in FIGS. The reliability of data in the external storage device 100 using 2 can be ensured. However, when the number of error bits becomes plural, in the method shown in FIGS. 11 and 12, the external storage using the flash memory is used. In some cases, the reliability of data in the apparatus 100 cannot be ensured.
[0059]
An example of ensuring the reliability of data in that case is the second embodiment of the present invention. The second embodiment will be described with reference to FIGS.
[0060]
In FIG. 14, the physical sector addresses that store the data of logical sector address 1 stored at addresses 1 and 1 + x of RAM 3 are 100100 and 100111, respectively. Therefore, the control circuit 4 operates as shown in FIG. Data in the management area 22 of the physical sector 20 with addresses 100100 and 100111 is read.
[0061]
However, as shown in FIG. 15, if the data in the management area 22 of the physical sector 20 with addresses 100100 and 100111 are 4, 6 respectively, they are logical sector addresses 1 from the host computer 200. Does not match.
[0062]
In the example shown in FIG. 14, the physical sector address stored in the addresses 1 and 1 + x of the RAM 3 is different in the lower 2 bits, so the physical sector address stored in the addresses 1 and 1 + x of the RAM 3 The data of the management area 22 of the physical sector 20 of 100101 and 100110, in which the value of the lower 2 bits is changed, is read, and the control circuit 4 confirms whether or not it matches the logical sector address 1 from the host computer 200.
[0063]
As shown in FIG. 15, if the data in the management area 22 of the physical sector 20 at addresses 100101 and 100110 are 2, 1, respectively, the physical sector 20 at address 100110 stores the data at logical sector address 1. Will be doing.
[0064]
Therefore, by the operation shown in FIG. 6, as shown in FIG. 16, the value of the physical sector address corresponding to the logical sector address 1 stored in the address 1, 1 + x of the RAM 3 is rewritten from 100100, 100111 to 100110, respectively. Correct the mapping table.
[0065]
When the mapping table is corrected, the data in the physical sector 20 at the address 100110 corresponding to the logical sector address 1 from the host computer 200 is sent to the host computer 200 by the operation shown in FIG.
[0066]
In this way, the reliability of data in the external storage device 100 using the flash memory 2 can be ensured even when there are a plurality of error bits generated in the RAM 3.
[0067]
If the physical sector 20 having the same logical sector address as the logical sector address from the host computer 200 does not exist in the management area 22 as in the operation described with reference to FIGS. 15 and 16, it is read from each mapping table. By changing the value of the bit having the same physical address value and performing the same operation as described with reference to FIGS. 15 and 16, the data of the external storage device 100 using the flash memory 2 can be changed. Reliability can be ensured.
[0068]
That is, according to the second embodiment of the present invention, even when the number of error bits is plural, the reliability of the mapping table is improved without requiring a separate ECC RAM for the mapping table, To realize an external storage device using a non-volatile memory capable of maintaining the reliability of data of an external storage device using a flash memory even when an error bit occurs in a RAM storing a mapping table Can do.
[0069]
As described above, in the present invention, the improvement of the data reliability of the external storage device 100 using the flash memory 2 when the mapping table is duplicated has been described. However, when the mapping table is multiplexed more than triple, The reliability of data in the external storage device 100 using the flash memory 2 can be improved.
[0070]
For example, when the mapping table is duplicated, the addresses of the RAM 3 for storing the physical sector address corresponding to the logical sector address a are a and a + x, but an error bit occurs in the same bit of the addresses a and a + x of the RAM 3 The occurrence of an error bit in the RAM 3 cannot be detected, and erroneous data is sent at the time of read access to the logical sector address a from the host computer 200.
[0071]
However, if the mapping table is multiplexed more than triple, it is very likely that there is at least one mapping table in which no error bit has occurred, so the physical table read from each mapping table is very likely to exist. When comparing the sector addresses, it is possible to almost certainly detect the occurrence of an error bit in the RAM 3 and to ensure the reliability of data in the external storage device 100 using the flash memory 2.
[0072]
If the mapping table is multiplexed more than tripled and the physical sector addresses read from the respective mapping tables do not match, the host computer 200 is determined by the majority of the physical sector addresses read from the respective mapping tables. If the physical sector address corresponding to the logical sector address from is determined, reading of the address read from each mapping table from the management area 22 of the physical sector 20 can be omitted, and the flash memory 2 for the host computer 200 is used. Thus, the access speed of the external storage device 100 can be increased.
[0073]
The above-described example is an example in the case where a flash memory is used as the nonvolatile memory. However, as the nonvolatile memory, not only the flash memory but also other memories such as an EEPROM and a ferroelectric memory are used. It is also possible to do.
[0074]
【The invention's effect】
As described above, according to the present invention, without requiring a separate ECC RAM for the mapping table, the reliability of the mapping table is improved, and an error bit is generated in the RAM storing the mapping table. Even in this case, an external storage device using a non-volatile memory that can maintain the reliability of data can be realized.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an external storage device according to a first embodiment of the present invention.
FIG. 2 is a diagram showing a configuration of the flash memory shown in FIG. 1;
FIG. 3 is a diagram showing a configuration of a physical sector shown in FIG. 2;
4 is a diagram showing a configuration of a RAM shown in FIG. 1. FIG.
FIG. 5 is a diagram showing a data write operation to the flash memory when data is written from the host computer to the external storage device;
FIG. 6 is a diagram illustrating an operation of writing data to a RAM for updating a mapping table.
FIG. 7 is a diagram showing a sending operation of a logical sector address for reading from a host computer to an external storage device.
FIG. 8 is a diagram showing a read access operation to a mapping table stored in a RAM.
FIG. 9 is a diagram showing a data read operation from the flash memory when a read access from the host computer to the external storage device is performed.
FIG. 10 is a diagram showing a read operation from a physical sector management area of a flash memory.
FIG. 11 is a diagram illustrating an example of data in a RAM that stores a mapping table.
FIG. 12 is a diagram illustrating an example of data in a management area of a physical sector of a flash memory.
FIG. 13 is a diagram illustrating an update operation of a mapping table in a RAM.
FIG. 14 is a diagram illustrating an example of data in a RAM storing a mapping table according to the second embodiment of the present invention.
FIG. 15 is a diagram illustrating an example of data in a management area of a physical sector of a flash memory according to the second embodiment of the present invention.
FIG. 16 is a diagram illustrating an update operation of a mapping table in a RAM.
[Explanation of symbols]
1 Host interface
2 Flash memory
3 RAM
4 Control circuit
5 Host interface bus
6 Host interface control line
7 Memory address bus
8 Memory data bus
9 Memory control line
20 physical sectors
21 Data area
22 Management area
100 External storage device using flash memory
200 Host computer

Claims (5)

In an external storage device using a non-volatile memory,
Using a nonvolatile memory as a storage medium, the inside of this storage medium is divided into physical sectors, which are units for reading and writing data, and the physical sectors are divided into a data area for holding write data from the host computer and a management area for management. In the area, the logical sector address that is the access address of the host computer is stored, and the mapping table of the logical sector address and the physical sector address in the storage medium in which the data of the logical sector address is stored is duplicated and mapped. When data is read from the host computer and stored in the table, the physical sector address corresponding to the logical sector address from the host computer is read from each of the duplicate mapping tables, and the read values match each other. The mapping table above If the contents are determined to be correct, the physical sector address data of the flash memory obtained from the mapping table is sent to the host computer, and the physical sector address values read from the duplicated mapping tables are different from each other, When the physical sector management area of the physical sector address read from the mapping table is accessed and there is a physical sector with the same logical sector address as the access address from the host computer, the data stored in this physical sector is An external storage device using a non-volatile memory, wherein the external storage device sends the data to the host computer and corrects the contents of the mapping table to the same logical sector address as the access address from the host computer 2. The external storage device using the non-volatile memory according to claim 1, wherein when the data is read from the host computer to the external storage device, the physical sector address values read from each of the duplicated mapping tables are different from each other, and each mapping is performed. If the physical sector of the physical sector address read from the table does not have a physical sector with the same logical sector address as the access address from the host computer in the management area, it is read from each duplicated mapping table. When the physical sector management area of the physical sector address is changed by changing the value of the bit different in the physical address, and there is a physical sector having the same logical sector address as the access address from the host computer, This physical sec External storage device using a nonvolatile memory, characterized by modifying the contents of the mapping table and sends the stored data to the data to the host computer. 3. The external storage device according to claim 2, wherein when data is read from the host computer to the external storage device, the physical sector address values read from each of the duplicated mapping tables are different from each other and read from each mapping table. There is no physical sector with the same logical sector address as the access address from the host computer in the physical sector of the physical sector address, and the physical address values read from each of the duplicated mapping tables are different from each other. If there is no physical sector with the same logical sector address as the access address from the host computer in the management area in the physical sector of the physical sector address with the bit value changed, read from each of the duplicated mapping tables Was The physical address value changes the value of the same bit, accesses the physical sector management area of the changed physical sector address, and there is a physical sector with the same logical sector address as the access address from the host computer An external storage device using a non-volatile memory characterized in that data stored in the physical sector is sometimes sent to the host computer and the contents of the mapping table are corrected. 4. An external storage device using a nonvolatile memory according to claim 1, wherein the mapping table is multiplexed more than tripled. 5. The external storage device using the non-volatile memory according to claim 4, wherein physical sector addresses read from each multiplexed mapping table are different from each other, and the physical read from each multiplexed mapping table is used. When the majority of the sector address values can be taken, the physical sector data of a large number of physical sector addresses is sent to the host computer, and the physical sector address value corresponding to the logical address from the host computer in the mapping table becomes the above-mentioned majority. An external storage device using a non-volatile memory, wherein the processing is terminated by rewriting to a physical sector address.

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