Patent ID: 8026744

Claim:
A clock signal switching device comprising: a first signal synchronization generation circuit for generating, based on a switching signal used in selecting either a first clock signal or a second clock signal and based on the first clock signal, a first mask signal and a first synchronized switching signal each synchronous with the first clock signal; a second signal synchronization generation circuit for generating, based on the switching signal and the second clock signal, a second mask signal and a second synchronized switching signal each synchronous with the second clock signal; a synchronized switching signal selection circuit for selecting either the first synchronized switching signal or the second synchronized switching signal as a selected switching signal based on the switching signal; a clock signal selection circuit for selecting either the first clock signal or the second clock signal as a selected clock signal based on the selected switching signal; a synthesized mask signal generation circuit for generating a synthesized mask signal having a masking portion where a masking portion of the first mask signal and a masking portion of the second mask signal overlap each other; and a clock signal mask circuit for masking the selected clock signal with the synthesized mask signal.