Patent ID: 8984321
Filing Date: 2015-03-17
Classification: G06F,H04L

Abstract:
1. A method of reducing jitter in a local clock of a synchronised USB device arising from re-clocking errors in repeater circuitry of a USB hub to which said USB device is attached, comprising: observing a USB data stream with said USB Hub, said data stream having a data stream bit rate; said USB Hub decoding a periodic signal structure in said USB data stream; said USB Hub generating an event signal in response to decoding of said periodic signal structure; and said USB Hub locking a frequency of a local clock of said USB Hub to said periodic event signal; wherein said local clock of said USB Hub is adapted to be a clocking source for said repeater circuitry of said USB Hub, said local clock having a frequency that is controlled to be substantially an integer multiple of a frequency of the data stream bit rate or such that a beat frequency between said local clock frequency and the data stream bit rate frequency is above a cutoff frequency of a low pass filter to avoid jitter due to beating effect caused by a difference in frequency between the data stream bit rate and said local clock.