PURPOSE: To detect that storage contents of a certain area are erased or changed and to attain the self-correction of said erasion or change of the storage contents, by writing the same information into plural areas and always having collations of storage contents among those areas.

CONSTITUTION: When a logic circuit 2 writes the information to an E2PROM 1, the same information is written to areas 1, 2 and 3 via an address buffer 3 and a data buffer 4. Then the circuit 2 reads the storage contents out of those three areas and decides that all storage contents are correct when all storage contents of three areas are coincident with each other. In case only the storage contents of the area 1 are different from those of other two areas, it is regarded that only the storage contents are erased or changed. Then the storage contents of the area 2 or 3 are written to the area 1 for correction the storage contents of the area 1.