Patent ID: 8359489
Filing Date: 2013-01-22
Classification: H03L

Abstract:
1. A method for automatically calibrating frequency, the method comprising: generating a series of digital data according to a pair of differential signals received from a high-speed Universal Serial Bus (USB) host and/or a full-speed Universal Serial Bus (USB) host; identifying a packet identification (PID) of a start of each frame according to the series of digital data; counting a first number of clocks generated by a reference oscillator during a first period between two consecutive packet identifications; dividing an output frequency of an oscillator by a predetermined number to generate a second period; counting a second number of clocks generated by the reference oscillator during the second period; generating a comparison result according to a difference between the first number of clocks and the second number of clocks; and generating a calibration signal to calibrate the output frequency of the oscillator according to the comparison result.