PURPOSE: To easily execute memory access even if a memory is extended by making it possible to execute memory selection according to only address information.

CONSTITUTION: A central control unit 11 is connected to N-pieces of memory blocks 14a to 14N through data buses 12, 13, and these memory blocks of N- pieces are driven and controlled by corresponding selection signals S1 to SN respectively. Then, the memory is selected according to the value of the remainder in division that the value of an address signal is divided by N, but since the value of the remainder in the division by N results in N-kinds from '0' to 'N-1', specified one among N-pieces of the memories can be selected according to the value of the remainder. Accordingly, the memory access can be executed according to only the address information without using any special information for memory selection. Thus, the memory access can be easily executed even if the memory is extended.