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US4820939A Expired / Lapsed US ⏱️ 0.0 years remaining

Finite metastable time synchronizer

Assignee: National Semiconductor Corp
•
Filing: 1987-11-24
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Granted: 1989-04-11
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Expires: 2007-11-24
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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.

References Cited (Backward Citations)

US4093878A Cited
US4398105A Cited
US4498176A Cited
US4529892A Cited
US4591737A Cited
US4667339A Cited
US4703200A Cited
GB2174856A Cited

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

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