Data Sampling for a Burst Mode Communications System
Abstract
A data sampling circuit and method is provided for a burst mode communication system. The circuit is an entirely digital circuit for reliably sampling an incoming stream of data to automatically adjust to variations in data stream clock rates and phase variations in the incoming data. The circuit includes a delay line with a plurality of serially coupled taps, each tap having a variable delay. One aspect of the invention includes increasing the delay time until the delay line captures at least one, but preferably two, full data cells of the incoming data stream (i.e., signal levels over at least one full clock period, defined by two transitions of the data stream), thereby aligning the receiving circuit with the frequency of the data stream clock. A second aspect of the invention includes outputting data from a tap that is selected to be midway between two regions of transitions of the incoming data stream, thereby aligning the receiving circuit with the phase of the data stream clock. The invention can, in alternative embodiments, track changes in the input data stream's phase/frequency. This involves updating the amount of delay in each tap of the delay line as well as picking the output of the appropriate tap to be used as the sampled data stream in response to changes in the input signal as well as changes in propagation delays of the circuits used to implement the delay line, resulting from temperature and voltage variations.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1994
- Accession Number
- ADA286098
Entities
People
- A. G. Rocco
Organizations
- Massachusetts Institute of Technology