Data and clock recovery system having a phase-locked-loop and which controls dynamic loop response of a data stream of unknown data format

摘要

A data and clock recovery system for capturing and processing serial data of a type wherein data bits of an unknown format are interleaved with clock bits utilizes a phase lock loop capable of being operated in a capture mode or a tracking mode. The data stream is compared with an internally generated reference signal, and error pulses having widths proportional to the phase error are generated. In the capture mode, these error pulses are differentially processed to produce a control voltage which varies the frequency of a VCO which in turn alters the reference frequency. In the tracking mode, phase error pulses of fixed widths are processed only if the data bits occur in fixed windows. Differential amplifying means provide adjustable gain control of the error pulses. Means are provided for digitally controlling the loop's dynamic response when switching between the capture and tracking modes.