Patent ID: 7541853

Claim:
A spread spectrum clock control apparatus which exercises control to supply a phase control signal to a phase interpolator which receives an input clock signal and varies the phase of an output clock signal in accordance with the phase control signal, and to frequency-modulate the output clock signal, the apparatus comprising: a first counter which receives a frequency-divided clock signal, changes over from up-counting to down-counting at a predetermined first count number, performs the up-counting and down-counting a prescribed number of times and outputs an output signal when a predetermined prescribed count number has been counted, said first counter having a state machine for managing transition of state; a second counter which receives the output signal from said first counter and changes over from up-counting to down-counting at a predetermined second count number, said second counter having a state machine for managing transition of state; and a controller which controls said phase control signal supplied to said phase interpolator, based upon count values of said first and second counters and state of said second counter.