Clock signal generating apparatus, clock signal generating method, and medium

Abstract

A clock signal generating apparatus detects a phase difference between an input reference clock signal and a feedback signal to output a control signal based on the phase difference, generates the clock signal with a frequency based on the output control signal, generates a pattern by switching, at a certain time interval, between a plurality of patterns of a second phase shift amount, adds a first phase shift amount to the second phase shift amount having the generated pattern, determines a phase to be selected, so that a cycle of the phase-shifted clock signal matches the cycle of a clock signal changed by the first phase shift amount to which the second phase shift amount is added, selects the determined phase from among a plurality of phases, and generates a phase-shifted clock signal whose signal level changes in the selected phase for output as the feedback signal.