Patent ID: 7065668
Filing Date: 2006-06-20
Classification: G06F

Abstract:
1. An information processing apparatus comprising: a first oscillating circuit that generates a first clock signal by oscillation and has a first oscillation stability time, the first oscillation stability time being a time required for frequency of the first clock signal becoming stable from the start of the oscillation, the first oscillating circuit being capable of operating with a power supply voltage equal to or higher than a first minimum operating voltage that is a minimum voltage required for operation of the first oscillating circuit; a second oscillating circuit that generates a second clock signal by oscillation and has a second oscillation stability time, the second oscillation stability time being a time required for frequency of the second clock signal becoming stable from the start of the oscillation, and being longer than the first oscillation stability time, the second oscillating circuit being capable of operating with a power supply voltage equal to or higher than a second minimum operating voltage that is higher than the first minimum operating voltage; a power supply voltage measuring circuit that measures power supply voltage; a switching circuit for, as long as the voltage measured by the power supply voltage measuring circuit is not higher than the second minimum operating voltage, selecting and outputting either the first clock signal or the second clock signal as the clock signal based on an elapsed time of the first oscillating circuit from the start of the oscillation and an elapsed time of the second oscillating circuit from the start of the oscillation, and as long as the voltage measured by the power supply voltage measuring circuit is higher than the second minimum operating voltage, selecting and outputting the second clock signal as a clock signal without considering an elapsed time of the first oscillating circuit; and an information processing unit for, in synchronism with the clock signal, performing information processing.