Clock control signal generation circuit, clock selector, and data processing device

Abstract

Provided are a technique for high-speed switching between clock signals different in frequency, and a clock-control-signal-generation circuit which serves to generate a control signal for clock switching in a clock selector operable to switch between clock signals including a first clock signal based on first and second clock-stop-permission signals and a clock-resume-permission signal. The clock-control-signal-generation circuit includes: a before-switching clock processing unit; and an after-switching clock processing unit. In each of the before-and after-switching clock processing units, the high-frequency clock processing subunit and the low-frequency clock processing subunit take partial charges of processing of clock signals involved in the switching respectively, whereby the processing is speeded up.