SEMICONDUCTOR MEMORY DEVICE HAVING BOTH RAM PORTION AND ROM PORTION

摘要

A semiconductor memory device having a RAM area and a ROM area at the same time is provided to replace a memory combination comprising a RAM and a ROM with one memory by varying the RAM and ROM area. A memory cell array(180) is equipped with the first variable memory area(180a) is accessed in the first and second operation mode, and the second variable memory area(180b) not accessed in the first or second operation mode. A memory controller(160) stores area information discriminating the first and second memory area, and generates memory control signals for controlling access to the first and second memory area. The first operation mode is a read operation mode and the second operation mode is a write operation mode. If the first memory control signal is generated in the memory controller, generation of the first and second operation mode enable signal is permitted. If the second memory control signal is generated, the generation of the first or second operation mode enable signal is restricted.