Method and system for multi-protocol clock recovery and generation
First Claim
Patent Images
1. A method of synchronizing an internal clock in a communications system comprising:
- a) extracting a timestamp from a received signal;
b) determining a difference between the timestamp and a time value of the internal clock; and
c) modifying a rate of change of the internal clock when the magnitude of the difference exceeds a rate of change threshold.
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Abstract
A method and system for synchronizing a receiver'"'"'s clock to the clock of a transmitter is disclosed herein. The disclosed system employs a digital clock synthesizer that uses patterns superimposed upon a receiver oscillator to synthesize a clock rate that approximates the clock rate of the transmitter. The pattern superimposed upon the receiver oscillator can be varied to allow for tracking of the variation in the transmitter clock.
292 Citations
17 Claims
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1. A method of synchronizing an internal clock in a communications system comprising:
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a) extracting a timestamp from a received signal;
b) determining a difference between the timestamp and a time value of the internal clock; and
c) modifying a rate of change of the internal clock when the magnitude of the difference exceeds a rate of change threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method of synchronizing an internal clock in a communications system comprising:
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a) extracting an original timestamp from a received signal;
b) setting a time value of the internal clock to a value derived from the original timestamp;
c) extracting a subsequent timestamp from the received signal;
d) determining the difference between the subsequent timestamp and the time value;
e) incrementing a fault counter if the magnitude of the difference exceeds a timing threshold;
f) resetting the clock to a value determined from the subsequent timestamp if the fault counter exceeds a fault threshold; and
g) modifying the rate of change of the internal clock if the difference exceeds a rate of change threshold and does not exceed a timing threshold.
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11. A clock synchronization system comprising
a timestamp extractor, for extracting a timestamp from a data stream, and for deriving a time value from said timestamp; - and
a clock controller, operatively attached to the timestamp extractor and an internal clock, said internal clock having a time value, for receiving select time values derived from a timestamp, and for digitally modifying the internal clock time value, in response to the timestamp derived time value. - View Dependent Claims (12, 13, 14, 15)
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16. An internal clock synchronization system comprising:
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a comparator, having first and second inputs for receiving first and second input signals, for determining a difference between the first and second input signals and providing at a comparator output a difference signal representative of the determined difference;
a clock controller, operatively connected to the comparator output, for receiving the difference signal and for digitally deriving a timing correction signal therefrom, and for providing the digitally derived timing correction signal at a clock controller output;
a timestamp extractor, operatively connected to the first input of the comparator, for extracting a timestamp associated with a data unit and for providing a signal indicative of a timestamp value to the first input of the comparator; and
a clock, operatively attached to the clock controller output for receing the timing correction signal and operatively attached to the second input of the comparator for providing a signal indicative of an internal time value. - View Dependent Claims (17)
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Specification