US4820939A
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Finite metastable time synchronizer
Assignee: National Semiconductor Corp
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Filing: 1987-11-24
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Granted: 1989-04-11
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Expires: 2007-11-24
Abstract
Abstract A synchronizer circuit having a predictable and finite metastable time, and thereby a finite sample interval, resulting in the minimization of the probability of errors in asynchronous information transfer.
Inventors
- 👤 Richard G. Sowell
- 👤 Robert Pieters
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 11:28
CPC Classifications
H; H03; H03K; H03K3/00; H03K3/02; H03K3/027; H03K3/037; H03K3/0372
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
93 words
A finite metastable time synchronizer for synchronizing an input data signal provided to a digital receiving circuit with a clock frequency of the receiving circuit, the synchronizer comprising; a master stage which receives the input data signal and is capable of providing two potential metastable points; and a slave stage capable of providing one potential metastable point and coupled to receive a master stage output via a data path which also serves as a feedforward/back path between the slave stage and the master stage to provide resolution of metastable conditions in the synchronizer.
Claim 2
Dependent Claim
93 words
A finite metastable time synchronizer for synchronizing an input data signal provided to a digital receiving circuit with a clock frequency of the receiving circuit, the synchronizer comprising; a master stage which receives the input data signal and is capable of providing two potential metastable points; and a slave stage capable of providing one potential metastable point and coupled to receive a master stage output via a data path which also serves as a feedforward/back path between the slave stage and the master stage to provide resolution of metastable conditions in the synchronizer.
Claim 3
Dependent Claim
33 words
A synchronizer as in claim 1 wherein the master stage comprises a Schmitt trigger and a cross-coupled inverter, such that the output of the Schmitt trigger is the input of the cross-coupled inverter.
Claim 4
Dependent Claim
35 words
A synchronizer as in claim 2 wherein the slave stage comprises a buffer inverter and a second cross-coupled inverter, such that the output of the buffer inverter is the input of the second cross-coupled inverter.
Claim 5
Dependent Claim
29 words
A synchronizer as in claim 3 wherein the w/L ratios of the transistors utilized in the Schmitt trigger are such that the Schmitt trigger dominates the second cross-coupled inverter.
Claim 6
Dependent Claim
147 words
A finite metastable time synchronizer for synchronizing an input data signal provided to a digital receiving circuit with a clock frequency of the receiving circuit, the synchronizer comprising: a. a first logic gate for receiving a data signal which is asynchronous to a clock signal and for providing an output signal upon receipt of the clock signal; b. a first stage which receives the output signal from the first logic gate and is capable of providing two potential metastable points; c. a second logic gate coupled to provide a data, feedforward/back path between the first stage and a second stage in response to the clock signal compliment; and d. a second stage coupled to receive a first stage output via the data path which also serves as a feedforward/back path between the second stage and the first stage to provide resolution of metastable conditions in the synchronizer.
Claim 7
Dependent Claim
147 words
A finite metastable time synchronizer for synchronizing an input data signal provided to a digital receiving circuit with a clock frequency of the receiving circuit, the synchronizer comprising: a. a first logic gate for receiving a data signal which is asynchronous to a clock signal and for providing an output signal upon receipt of the clock signal; b. a first stage which receives the output signal from the first logic gate and is capable of providing two potential metastable points; c. a second logic gate coupled to provide a data, feedforward/back path between the first stage and a second stage in response to the clock signal compliment; and d. a second stage coupled to receive a first stage output via the data path which also serves as a feedforward/back path between the second stage and the first stage to provide resolution of metastable conditions in the synchronizer.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-04-10 | 1992-10-10 | 1993-04-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-04-10 | 1996-10-10 | 1997-04-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-04-10 | 2000-10-10 | 2001-04-11 | $7700.00 | Window Closed / Lapsed |