FW: FW: [SI-LIST] : METASTABILITY IN FLIP FLOPS

Johnson, David (david.johnson@intel.com)
Thu, 15 Jul 1999 13:12:36 -0700

As time allows, I will continue searching for the very old magazine article
that mentioned a 4-hour metastable experimental result (in a low-noise
environment); it probably goes back at least 20 years, or whenever the 74S
logic family was the state of the art.

Meanwhile, I did a quick WWW search (marvelous technology!) on "metastable"
using the http://www.hotbot.com search engine, and I readily found some
interesting references. Copies of the search results are included below,
along with hotlinks to the corresponding web pages. According to the page
from Dr. Haggard at Tennessee Tech University (notes for ECE 411 lectures),
a metastable state could theoretically last forever in the absence of noise.
It's the ever-present electrical noise that eventually nudges the circuit
out of a metastable condition.

One of the purposes of the 74S experiments, as I recall, was to find out
just how bad metastability can really be. Since that time, of course, the
industry has made huge strides in keeping metastable effects as controlled
as possible.

----- Dave W Johnson

1. App Note Abstract: METASTABLE RESPONSE IN 5-V LOGIC CIRCUITS
>>Semiconductor Home>Applications> Application Report Abstract METASTABLE
RESPONSE IN 5-V LOGIC CIRCUITS This document describes metastable response
in digital circuits. After a definition of a metastable state, a test
circuit is provided, its..
99% 6/17/99 http://www.ti.com/sc/docs/psheets/abstract/apps/sdya006.htm
See results from this site only.

5. Bistable and Metastability
Metastability could last forever, but noise usually pushes towards a stable
state (HIGH or LOW).Noise in a stable state returns it to the same stable
state.Analogous to a ball on a
http://digital5.ece.tntech.edu/411f97/Lectures/ch7/tsld011.htm
See results from this site only.

[See also http://digital5.ece.tntech.edu/411f97/Lectures/ch7/ --- dwj]

-----Original Message-----
From: Jake Salmi [mailto:salmi@minn.teradyne.com]
Sent: Thursday, July 15, 1999 11:25 AM
To: si-list@silab.eng.sun.com
Subject: Re: FW: [SI-LIST] : METASTABILITY IN FLIP FLOPS

A pretty good reference for this is
motorola Ap note AN1504.

js

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