STORAGE DEVICE AND DATA WRITE CONTROL METHOD

PROBLEM TO BE SOLVED: To secure data restorability, prevent a reduction in responsiveness at data write, and effectively utilize the capacity in a semiconductor memory having a unit of erase larger than the unit of write. SOLUTION: The block of the semiconductor memory 2 is divided into a data page 222 and an alternative page 223, and the semiconductor memory 2 is divided into a data block 22 and an alternative block 23. When a data overwrite request is received from the outside and the capacity of the alternative page 223 is sufficient for an amount of data to be written, overwrite data is written on the alternative page 223. On the other hand, when the capacity of the alternative page 223 is insufficient, the data of the data block 22 updated with the overwrite data is written in the alternative block 23. The data includes management data 2322 having a logical address of the old data, which is obtained by incrementing a counter number thereof. COPYRIGHT: (C)2010,JPO&INPIT