Clock generator and a method of generating a clock signal
AssigneeSkymedi Corporation
InventorsChing-Cheng Wu, Chih-Yu Chuang
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Abstract
The present invention is directed to a clock generator and a method of generating a clock signal. A digital control oscillator (DCO) generates a clock signal. A first frequency calibration unit extracts a periodic signal and determines a frequency error quantity between the extracted periodic signal and a derived clock signal. A second frequency calibration unit generates a coarse tuning signal when an absolute value of the frequency error quantity is greater than a first predetermined threshold, and generates a fine tuning signal when the absolute value of the frequency error quantity is less than a second predetermined threshold.
Claims17
A clock generator, comprising:
- a digital control oscillator (DCO) configured to generate a clock signal;
- a first frequency calibration unit configured to determine validity of a receiving signal, and detect and extract a periodic signal enclosed in the receiving signal, wherein the first frequency calibration unit determines a frequency error quantity between the extracted periodic signal and a derived clock signal derived from the clock signal when the receiving signal is valid;
- and
- a second frequency calibration unit configured to generate a coarse tuning signal to the DCO according to the frequency error quantity when an absolute value of the frequency error quantity is greater than a first predetermined threshold;
- wherein the second frequency calibration unit generates a fine tuning signal to the DCO according to the frequency error quantity when the absolute value of the frequency error quantity is less than a second predetermined threshold that is less than the first predetermined threshold.
A method of generating a clock signal, comprising:
- determining whether a link has been built between a host and a device;
- comparing an extracted periodic signal and a clock signal to determine frequency error quantity;
- adjusting a coarse tuning signal when an absolute value of the frequency error quantity is greater than a first predetermined threshold;
- comparing the clock signal with a receiving signal when the absolute value of the frequency error quantity is less than a second predetermined threshold that is less than the first predetermined threshold, thereby generating an up/down signal;
- adjusting a fine tuning signal according to the frequency error quantity and comparison result between the clock signal and the receiving signal;
- and
- checking the frequency error quantity when no updating about the up/down signal within a predetermined duration, until the frequency error quantity is greater than the second predetermined threshold.
Dependencies are inferred from the claim text.