PURPOSE: To prevent the cycle disturbance occurring among devices by continuing a reset state until a reference clock is stably supplied to release this reset state after the stable supply is secured with said reference clock and at the same time restarting the resetting action after a fixed time to initialize the phase of an internal clock of each device.

CONSTITUTION: A period of time during which a reference clock 2 received from an external oscillator 11 is stabilized is decided by an RC time constant circuit. Then a first reset signal 7 is transmitted to each device via an OR circuit 16 in a period A during which a signal 1 is stabilized by a waveform shaping circuit 14. When the clock 2 is stabilized, the clocks of the oscillator 11 are counted by a counter 13 via an FF 12. Then an ON signal B is transmitted via the OR secured between signals 4 and 5 when the count value of the counter 13 reaches a prescribed level. The counter 13 transmits again a resetting signal 4 after the output of the signal B and the count value of the counter 13 is equal to a fixed level. Then the counter 13 applies the second resetting action to each device via the OR secured between both signals 4 and 5.