PURPOSE: To prevent the destruction of a RAM contents at the time of the running-away of the system in case of the RAM and to prevent the leaking of the data in case of a ROM by making the memory which can be accessed except the person concerned.

CONSTITUTION: The comparing result of address data Ak and fuse data inputted during the Tk period is latched to a flip-flop 3 by the fall clock of a signal, the inverse of CE, only when the comparing result is coincident at a comparing device 2, there state buffers 4 come to be enable and the regular access is executed during the Tp period. When the address input Ak during the Tk period and the fuse data are dissident, the buffers 4 do not come to be enable and the access of the Ap address cannot be executed. The method of the program of a fuse 5 can be easily realized by the melting, etc., with the laser.