| abstract |
The present invention is directed to shorten time required to backup stored information to be erased in a nonvolatile memory. A nonvolatile memory has a plurality of memory mats on which a rewriting operation can be performed on a page unit basis, and a memory control circuit capable of performing a byte access control on the memory mats. The memory control circuit makes a plurality of memory mats operate in the byte access control, at the time of rewriting data, merges data read from a selected page in one memory mat with write byte data, writes the resultant data to a corresponding page selected in the other memory mats and, at the time of reading, reads the data from the valid page which is most recently rewritten selected in the plurality of memory mats. The selected page in one memory mat has substantial backup data which has not been subjected to the rewriting for a selected page in another memory mat. |