PURPOSE: To shorten the CPU restarting time by outputting a reset pulse from at least one of a watchdog timer and a runaway factor detecting circuit and simultaneously informing the runaway factor to a CPU from a holding circuit.

CONSTITUTION: The runaway factor detecting circuits 3 and 4 are provided to detect the different runaway factors together with a holding circuit 6 which holds the outputs of both circuits 3 and 4 in addition to a watchdog timer. When a CPU 1 has a runaway, a reset pulse is outputted from at least one of these timer and circuits 3, 4 and 6. Simultaneously, the circuit 6 informs the runaway factor to the CPU 1. Thus the restart processing is carried out in response to each runaway factor and the restart processing time is shortened.