PURPOSE: To send out the output of the oscillator of an LSI for a microcomputer in the beginning of oscillator operation after an unstable period, by connecting a capacitor to an external terminal for control over the operation and stopping of the oscillator.

CONSTITUTION: A capacitor C is connected to an external terminal 7 for oscillator control provided to an LSI. When an oscillation control signal PC is at a level L, an inverter 2 is turned off and the output point (b) of an inverter 8 is at a level H, so an oscillating element 1 is not in operation, resetting a reset priority FF6. When the signal PC goes up to the level H, the inverter 2 is turned on to form the feedback circuit including the oscillating element 1, which starts oscillating. At the same time, a point (b) beyond the inverter 8 has slow transition to the level L through the capacitor C. Then, the FF6 is set and a gate 3 turns on to send the oscillation output of the oscillating element 1 to a CPU, etc., which is not shown in the figure.