Patent ID: 7321244

Claim:
A clock switching device which switches a clock to be supplied to an information processing device, comprising: a unit which detects, out of a plurality of clock pulses applied, abnormality in a waveform of one of said plurality of clock pulses applied that is being output; a unit which, when said abnormality in a waveform is detected, switches to and outputs other clock pulse whose phase is matched with a phase of one of said plurality of clock pulses applied that is being output; an abnormality detection unit which detects lack of coincidence in a logical level between a current clock pulse and a one-cycle preceding clock pulse as abnormality in a waveform on the basis of said plurality of clock pulses; a phase adjustment unit for switching which adjusts the phase of said other clock pulse to the phase of said clock pulse being output, a switching unit which switches to and outputs said other clock pulse whose phase is adjusted by said phase adjustment unit for switching based on detection of lack of coincidence in a logical level by said abnormality detection unit; and a phase adjustment unit for detection which matches a phase of a current clock pulse and a phase of a one-cycle preceding clock pulse on the basis of said plurality of clock pulses, wherein said phase adjustment unit for detection outputs a clock pulse being output and other clock pulse to said phase adjustment unit for switching.