Oscillator circuit and semiconductor integrated circuit device

An oscillator circuit with an RC circuit or a crystal resonator connected thereto as an external component, for generating a clock signal using said RC circuit or said crystal resonator, said RC circuit comprising a resistive element and a capacitor element, said oscillator circuit comprising:

• a crystal oscillating circuit for being connected in parallel with said crystal resonator and for generating the clock signal using said crystal resonator;
• an RC oscillating circuit for being connected in parallel with said resistive element and for generating the clock signal using said RC circuit;
• a control signal generation circuit for bringing one terminal of said external component to a ground potential in response to input of a reset signal;
• a switch circuit for connecting said crystal oscillating circuit to said crystal resonator in parallel upon receipt of a first signal and connecting said RC oscillating circuit to said resistive element in parallel upon receipt of a second signal, said first signal being a selection signal for operating said crystal oscillating circuit and said second signal being a selection signal for operating said RC oscillating circuit;
• and
• a selection signal generation circuit for supplying the first signal to said switch circuit when a current flowing through said external component is less than a predetermined value and supplying the second signal to said switch circuit when the current is not less than the predetermined value, said selection signal generation circuit being connected to the other terminal of said external component in response to input of the reset signal.