an oscillator circuit which generates an oscillator signal that ensures the generation of a stable internal supply voltage . the oscillator circuit has a periodic circuit which includes a switch circuit . a method of controlling the oscillator circuit includes the steps of operating the periodic circuit using the switch circuit in response to a first control signal when the first control signal is in a first state to generate a first oscillator signal having a first frequency , and operating the periodic circuit using the switch circuit in response to a second control signal when the first control signal is in a second state to generate a second oscillator signal having a period synchronized to a period of the second control signal having a second frequency .