US4608702A
Expired / Lapsed
US
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Method for digital clock recovery from Manchester-encoded signals
Assignee: Advanced Micro Devices Inc
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Filing: 1984-12-21
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Granted: 1986-08-26
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Expires: 2004-12-21
Abstract
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.
Inventors
- 👤 Frederic J. Hirzel
- 👤 Roy J. Levy
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 21:24
CPC Classifications
H; H04; H04L; H04L7/00; H04L7/02; H04L7/033; H04L7/0331; H03; H03M; H03M5/00; H03M5/02; H03M5/04; H03M5/06; H03M5/12
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
150 words
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.
Claim 2
Independent Claim
150 words
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.
Claim 3
Dependent Claim
73 words
The clock-recovery method of claim 1 wherein said recovered-clock generation steps (a) and (d) further call for sequencing an n-state counter, each state transition occuring at a T/n interval, step (a) further calling for resetting said n-state counter, and step (d) further calling for a one-state-skipping transition, a next-state transition, or a same-state transition of said n-state clock-recovery counter depending on whether said "zero-crossing" occurred before, coincident with, or after, respectively, said "mid-point".
Claim 4
Dependent Claim
81 words
The clock-recovery method of claim 2 wherein n=16 and said comparison step (c) further calls for generating SHORTEN, CENTER, LENGTHEN signals according to the equations: SHORTEN=f(state) CENTER=g(state) LENGHTEN=h(state) wherein f, g and h are Boolean functions of said n-state counter, and said recovered-clock generation step (d) further calls for generating a recovered-clock signal having a period shorter-than, equal to, or greater-than said period of said most-recently-generated recovered-clock signal depending on whether LENGTHEN. CENTER, CENTER, or SHORTEN.CENTER is a HIGH signal, respectively.
References Cited (Backward Citations)
US3778550A
Cited
US4385396A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1989-08-25 | 1990-02-24 | 1990-08-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-08-25 | 1994-02-24 | 1994-08-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-08-25 | 1998-02-24 | 1998-08-26 | $7700.00 | Window Closed / Lapsed |