Clock signal generator

1. A clock signal generator comprising:

a signal generation unit that outputs a first clock signal composed of a single frequency component; and

a phase angle detection unit that detects phase angles of the first clock signal by comparing a plurality of threshold values set within the amplitude of the first clock signal with instantaneous values of the first clock signal, and generates a second clock signal by determining rising and/or falling edges of the signal according to the detected phase angles,

the rising and/or falling edges being determined by using a first group of threshold values in a first half of the cycle of the first clock signal and using a second group of threshold values in a latter half of the cycle of the first clock signal, the first group of threshold values and the second group of threshold values being shifted from each other.

2. The clock signal according to claim 1 , wherein the second clock signal is used as a transmission clock signal for a signal bus, and a maximum amplitude value of the waveform of the first clock signal is determined according to a maximum value of a multilevel signal passing through a data line in the signal bus.

3. The clock signal generator according to claim 1 , wherein the first clock signal is a sine wave.

4. The clock signal generator according to claim 1 , wherein the comparison between the threshold values and the instantaneous values is performed by a plurality of window comparators.

5. The clock signal generator according to claim 4 , wherein a degree of the shift of the first group of threshold values relative to the second group of threshold values is determined based on detection ranges of the plurality of window comparators.

6. The clock signal generator according to claim 4 , wherein a degree of the shift of the first group of threshold values relative to the second group of threshold values is determined based on upper and lower limits of the plurality of window comparators.