| 摘要 |
A plurality of data areas and management areas corresponding to the data areas are formed in a flash ROM. The management area consists of a sector number, a busy state flag, and a used state flag. To write data, a write instruction having a logical sector number indicating a data write destination is received, the data is written in one of writable data areas, and the logical sector number is written in the corresponding management area. To read out data, a read instruction having a logical sector number indicating a data read source is received, a management area storing the logical sector number is retrieval-accessed, and data stored in a data area corresponding to the retrieval-accessed management area is read out. In this manner, a data read.write unit (storage unit) smaller than an erase unit can be managed in a flash ROM. This makes a flash ROM with a large erase unit compatible with a file system.
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