| 摘要 |
This is an external storage device for which erase is performed as units of blocks comprising a plurality of pages, and that uses flash memory that uses this page as the minimum unit for reading and writing data, the flash memory comprising a redundant part area for storing codes for performing error correction of specified bit counts for each of the pages, and a bit substitute area at specified areas within the flash memory. The external storage device includes a bit management unit existed within the page and that is for allocating the address of the bit substitute area to the defective bits that are beyond scope of the page unit error correction, and a block control unit that replaces the defective bit with the bit within the bit substitution area and performs reading and writing of the data to the block containing the defective bits. With this external storage device, it is possible to improve the use efficiency of the flash memory.
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