When a voltage monitoring circuit detects that a supplied voltage is in a state of being less than a certain voltage at a time of performing writing of data with respect to a memory cell of a memory core having a refresh function, a flag is set in a register circuit, an address at which the writing is performed is held, and the memory core is made to execute rewriting by a refresh operation with respect to the held address, in accordance with the flag set in the register circuit, thereby enabling an increase in speed of operation while securing a retention life of memory data, and enabling a reduction in power consumption without lowering a processing capability even if the supplied voltage is lowered.