To guarantee the power of a flash memory for a fixed period even when the interruption of power occurs after data transfer and to guarantee the write of data by directly connecting a power storage means to the power supply terminal of the flash memory and connecting it through a back flow prevention means to a main power unit.

There is the case that the flash memory 24 is in the middle of receiving the data and transferring the data to a memory array 27 by a sequential circuit 26 at the moment when the power is interrupted. At the time, the power stored in a capacitor 23 is supplied to the flash memory 24, and since the back flow of a current is prevented by a diode 22, the power stored in the capacitor 23 is not consumed by other electrical parts 25. Thus, the power stored in the capacitor 23 is supplied only to the flash memory 24. By the power supplied from the capacitor 23, the sequential circuit 26 continues an operation even after the power is interrupted and the transfer of the data to the memory array 27 is ended.