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From: wmb@sun.uucp (Mitch Bradley)
Newsgroups: net.micro
Subject: net.digital - is FAST really needed
Message-ID: <1135@sun.uucp>
Date: Tue, 22-May-84 11:48:38 EDT
Article-I.D.: sun.1135
Posted: Tue May 22 11:48:38 1984
Date-Received: Wed, 23-May-84 19:32:10 EDT
References: <2539@ecsvax.UUCP>
Organization: Sun Microsystems, Inc.
Lines: 20

Yes, it's very useful.  In particular, a FAST flip-flop is the
best synchronizer I know of.  F74's and F374's settle out of
a metastable condition (caused by missing a setup or hold time)
in about 35 nsec, whereas S74's take about twice as long.  LS is
just about hopeless in this case.

FAST is also very useful when you need short prop delays.  It uses 
significantly less power than Schottky, with similar delays.

One area where FAST is not so good is in driving busses.  The fall
time is so short that it is difficult to control crosstalk on a bus
driven by FAST logic.  I talked to the product planning guy from Fairchild
yesterday and mentioned this problem.  He says that other customers
have mentioned this also, so thay are going to think about doing
a class of FAST parts with reduced edge rates.

Mitch Bradley
Sun Microsystems, Inc.
sun!wmb