Jitter reduction method and apparatus for distributed synchronised clock architecture

摘要

A method of reducing jitter in a local clock of a synchronised USB device attached to a USB Hub, the USB Hub having a local clock and repeater circuitry, comprising: observing a USB data stream with the USB Hub, the data stream having a data stream bit rate; the USB Hub decoding a periodic signal structure in the USB data stream; the USB Hub generating an event signal in response to decoding of the periodic signal structure; and the USB Hub locking a frequency of the local clock of the USB Hub to the periodic event signal. The local clock of the USB Hub is adapted to be a clocking source for the repeater circuitry of the USB Hub at substantially an integer multiple of a frequency of the data stream bit rate.