Patent ID: 6859079
Filing Date: 2005-02-22
Classification: G06F

Abstract:
1. A semiconductor device comprising: first internal clock generation circuitry for producing a first internal clock signal synchronized with a basic clock signal, said first internal clock generation circuitry including a first phase difference detecting circuit for detecting a phase difference between said basic clock signal and said first internal clock signal to produce a first control signal in accordance with the phase difference, and a first clock generating circuit having an operation speed thereof determined in accordance with the first control signal output by said first phase difference detecting circuit and operating in accordance with the operation speed to produce a clock signal corresponding to said basic clock signal as said first internal clock signal; and second internal clock generation circuitry for producing a second internal clock signal synchronized with a synchronization target signal, said second internal clock generation circuitry including a second phase difference detecting circuit for detecting a phase difference between said synchronization target signal and said second internal clock signal to produce a phase error signal in accordance with the phase difference, a control circuit for producing a second control signal in accordance with at least either of said first control signal and a signal corresponding to said first control signal and said phase error signal, and a second clock generating circuit having an operation speed thereof determined in accordance with the second control signal output by said control circuit and operating in accordance with the operation speed to produce a signal corresponding to said synchronization target signal as said second internal clock signal, wherein said second internal clock generation circuitry further includes a frequency difference detecting circuit for detecting a frequency difference between said second internal clock signal and said synchronization target signal to produce and apply to said control circuit a frequency error signal in accordance with the frequency difference, and said control circuit produces said second control signal in accordance with said frequency error signal, said phase error signal and either of said first control signal and the signal corresponding to said first control signal.