US 4,608,702 AGranted

Method for digital clock recovery from Manchester-encoded signals

AssigneeAdvanced Micro Devices, Inc.

InventorsFrederic J. Hirzel, Roy J. Levy

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Abstract

A method for rapidly recovering the clock from Manchester-encoded signals using simple digital techniques is provided for use in an inexpensive Manchester-encoding receiver. The received Manchester-encoded signal is monitored to determine zero-voltage crossing. At each such crossing the frequency of the recovered clock is adjusted by comparing the occurrence of the zero-crossing with respect to the midpoint of the period of the presently-generated recovered clock. Shorten, center or lengthen adjustment signals are generated as a result of this comparison which are used to shorten or lengthen, by 1/16 increments of the inter-bit period of the received data signal, the period of the next-generated recovered-clock. The method is readily implemented as a sixteen-stage programmable counter providing a phase-locked loop.

Claims3

Dependent claims

A method of recovering the clock from Manchester-encoded signals on a pair of signal lines said Manchester-encoded signals being a serial Manchester-encoded stream having an inter-bit period T, comprising the steps of:

a. generating a recovered-clock signal having a period of approximately T;
b. detecting "zero-crossing" when the signed voltage differential on said pair of signal lines becomes zero;
c. comparing the occurrence of the "zero-crossing" of the received signals with the occurrence of the "mid-point" T/2 of the period of the most-recently-generated recovered-clock signal;
d. generating a recovered-clock signal having a period shorter than, equal to, or greater than the period of the most-recently-generated recovered-clock signal depending on whether the comparison step (c) indicated the occurrence of said "zero-crossing" to be before, coincident with, or after, respectively, said "mid-point" T/2 occurrence of said most-recently-generated recovered-clock signal;
and
e. repeating steps (b), (c) and (d) on the next-received serial signal.

3 more elements

Dependencies are inferred from the claim text.