PURPOSE: To realize a quick rise of a system by preparing a RAM backed up by a battery or a nonvolatile RAM in addition to a RAM which receives a writing action with an instruction of a microprocessor and writing the initialization value also into the backed-up RAM or the nonvolatile RAM.

CONSTITUTION: An RS flip-flop 10 connected to a push-button switch 9 for start instruction of initialization is prepared together with an AND gate 11, a RAM 12 backed up by a battery, etc. The power supply voltage Vcc is applied to a power supply terminal Vcc from a battery 13. The terminal Vcc is connected to a microprocessor 1 via a data bus D and an address bus AD. A read instruction line -RD is connected to a read input -RD. The signal of a write instruction line -WR is inverted through an inverter 11b and connected to the input of the other side of an AND gate 11a and then connected to the write input -WR of the RAM 12 through an inverter 11c. The RAM 12 stores the same initialization value as a RAM 3. The storage value of the RAM 12 is not destroyed despite the runaway of the microprocessor 1.