Abstract: An operation-control circuit for controlling write into a memory cell in a memory cell array is provided between the memory cell array and data input and output buffers. When either /ORE signal or /ANDE signal and WE signal are activated at the time of read cycle, the operation-control circuit conducts OR or AND operation between a data stored in a memory cell array and a data to be written thereinto, and a data in the data input buffer is written into the memory cell array in accordance with the result of the aforementioned logical operation.