OSCILLATION CIRCUIT

摘要

A first switch (SW1) is connected in series between a first capacitor (1) and a grounding wire, and when an RTC oscillator is connected and an IC chip (10) is configured as an external input buffer circuit, the first switch (SW1) is turned off. Thus, the first capacitor (1) and a second capacitor (2) are prevented from being connected in parallel to a resonance capacitor of the RTC oscillator, and the first and the second capacitors (1, 2) are prevented from configuring a part of the resonance circuit of the oscillator. When an exclusive crystal oscillator is connected and the IC chip (10) is configured as a part of the oscillator, the first switch (SW1) is turned on and the first and the second capacitors (1, 2) configure a part of the resonance circuit.