PURPOSE: To process abnormality caused by a microcomputer by storing information of a runaway of the microcomputer in a RAM without breaking down data stored in the RAM already.

CONSTITUTION: By a runaway detecting signal at the time of runaway of a microcomputer 1, the microcomputer 1 is reset, and also, the microcomputer 1 is allowed to execute an interruption processing by delaying by the time required for completion of reset with a delaying circuit 5, and by this interruption processing, information of the runaway, a RAM active signal and a write permitting signal are sent out of the microcomputer 1, and by OR of the runaway detecting signal and the RAM active signal, a chip select signal is generated, and also, by inputting an AND signal of this chip select signal and the write permitting signal, and the information of the runaway to a pointer control part 6, a write address of a RAM 3 is changed, and the information of the runaway is stored in the RAM 3.