EP0248551A2
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EP
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Synchronization of asynchronous data signals
Assignee: Nortel Networks Ltd
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Filing: 1987-05-12
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Granted: —
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Expires: 2007-05-12
Abstract
Abstract In a synchronous network, asynchronous data signals are synchronized using positive/negative stuffing under the control of stuff request signals which are produced in dependence upon the phase difference between the asynchronous and synchronized data signals as compared to respective threshold values. The threshold values are cyclically changed in a manner to produce additional stuffing, not necessitated by the asynchronous frequency difference, whereby the frequency of jitter, due to stuffing, in the synchronized data signal is increased. The increased frequency jitter is filtered out in an already-provided phase locked loop
Inventors
- 👤 James Angus Mceachern
- 👤 Wayne Davy Grover
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 06:47
CPC Classifications
H; H04; H04J; H04J3/00; H04J3/02; H04J3/06; H04J3/07; H04J3/076
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
84 words
A method of synchronizing an asynchronous data signal to produce a synchronized data signal comprising the steps of: stuffing the asynchronous data signal in dependence upon a stuff request signal to produce the synchronized data signal; producing the stuff request signal in dependence upon the magnitude of a phase difference between the asynchronous and synchronized data signals in comparison to at least one threshold value; and varying the theshold value to increase the frequency of jitter, due to stuffing, in the synchronized data signal.
Claim 2
Independent Claim
84 words
A method of synchronizing an asynchronous data signal to produce a synchronized data signal comprising the steps of: stuffing the asynchronous data signal in dependence upon a stuff request signal to produce the synchronized data signal; producing the stuff request signal in dependence upon the magnitude of a phase difference between the asynchronous and synchronized data signals in comparison to at least one threshold value; and varying the theshold value to increase the frequency of jitter, due to stuffing, in the synchronized data signal.
Claim 3
Dependent Claim
33 words
A method as claimed in claim 1 wherein the threshold value is varied cyclically and periodically with a period during which a plurality of stuffs of the asynchronous data signal can be effected.
Claim 4
Dependent Claim
16 words
A method as claimed in claim 2 wherein said period is not more than about 5ms.
Claim 5
Dependent Claim
31 words
A method as claimed in claim 2 or 3 wherein the threshold value is varied with a predetermined waveform having a progressively changing level at least during part of each cycle.
Claim 6
Dependent Claim
15 words
A method as claimed in claim 4 wherein said waveform is a substantially sawtooth waveform.
Claim 7
Dependent Claim
15 words
A method as claimed in claim 4 wherein said waveform is a substantially triangular waveform.
Claim 8
Dependent Claim
15 words
A method as claimed in claim 4 wherein said waveform is a substantially sinusoidal waveform.
Claim 9
Independent Claim
35 words
A method as claimed in any of claims 4 to 7 wherein the phase difference magnitude and the threshold value are digital quantities and the waveform is constituted by a changing count of a counter.
Claim 10
Independent Claim
89 words
A method as claimed in any of claims 1 to 8 wherein the asynchronous data signal is stuffed using positive and negative stuffing in dependence upon positive and negative stuff request signals to produce the synchronized data signal, the positive and negative stuff request signals are produced in dependence upon the magnitude of the phase difference between the asynchronous and synchronized data signals in comparison to respective threshold values, and the threshold values are varied thereby to produce additional stuff requests in the positive and negative stuff request signals.
Claim 11
Dependent Claim
29 words
A method as claimed in claim 9 wherein the threshold values differ by, and are varied in amplitude by, an amount corresponding to a phase difference of about 360°.
Claim 12
Dependent Claim
23 words
A method as claimed in claim 9 wherein the threshold values differ by an amount corresponding to a phase difference of about 720°.
Claim 13
Dependent Claim
73 words
Synchronizing apparatus comprising: stuffing means responsive to a stuff request signal for stuffing an asynchronous data signal to produce a synchronized data signal; means for producing the stuff request signal in dependence upon the relative phases of the asynchronous and synchronized data signals in comparison to at least one threshold value; and means for varying the threshold value whereby the frequency of jitter, due to stuffing, in the synchronized data signal is increased.
Claim 14
Dependent Claim
73 words
Synchronizing apparatus comprising: stuffing means responsive to a stuff request signal for stuffing an asynchronous data signal to produce a synchronized data signal; means for producing the stuff request signal in dependence upon the relative phases of the asynchronous and synchronized data signals in comparison to at least one threshold value; and means for varying the threshold value whereby the frequency of jitter, due to stuffing, in the synchronized data signal is increased.
Claim 15
Dependent Claim
45 words
Apparatus as claimed in claim 12 wherein the means for varying the threshold value comprises means for generating a cyclical waveform having a progressively changing level at least during part of each cycle, and means for changing the threshold value in dependence upon said waveform.
Claim 16
Dependent Claim
19 words
Apparatus as claimed in claim 13 wherein the means for generating a cyclical waveform comprises a sawtooth waveform generator.
Claim 17
Dependent Claim
27 words
Apparatus as claimed in claim 13 or 14 wherein the threshold value is a digital quantity and the means for generating a cyclical waveform comprises a counter.
Claim 18
Dependent Claim
29 words
Apparatus as claimed in claim 15 and including means for supplying to the counter a clock signal which is related to the timing of one of the data signals.
Claim 19
Dependent Claim
110 words
Apparatus as claimed in any of claims 12 to 16 wherein the stuffing means responsive to positive and negative stuff request signals for effecting positive and negative stuffing of the asynchronous data signal to produce the synchronized data signal, the means for producing the stuff request signal comprises means for producing the positive and negative stuff request signals in dependence upon the magnitude of the phase difference between the asynchronous and synchronized data signals in comparison to respective threshold values, and the means for varying the threshold value comprises means for cyclically changing the threshold values thereby to produce additional stuff requests in the positive and negative stuff request signals.
References Cited (Backward Citations)
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