Path: utzoo!attcan!uunet!munnari.oz.au!mullian!gja
From: gja@mullian.ee.mu.oz.au (Grenville Armitage)
Newsgroups: sci.electronics
Subject: Re: Analog and Digital Design
Message-ID: <6012@munnari.oz.au>
Date: 12 Nov 90 23:16:34 GMT
References: <11242.2730bfd5@ecs.umass.edu> <1990Nov2.223926.26095@ameristar> <47O.029T03cv01@JUTS.ccc.amdahl.com> <1990Nov12.045429.20147@ncsuvx.ncsu.edu> <32696@netnews.upenn.edu>
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In article <32696@netnews.upenn.edu> touch@dsl.cis.upenn.edu (Joe Touch) writes:
>In article <1990Nov12.045429.20147@ncsuvx.ncsu.edu> dsh@csl36h.csl.ncsu.edu.UUCP (Doug Holtsinger) writes:

>>Digital design is getting to be much more than just ones and zeros.
>>Just try designing a digital board to run at > 30 Mhz without analyzing 
>>board trace delays, or dealing with reflection problems, etc..

>You don't have to get into analog problems to require 'the right
>approach'. I've seen boards built to 150 Mhz without board trace
>delay or reflection requiring analog analyis.

I'd be interested to know how this was done without any reference to
the analog nature of signals at such frequencies. Even generalised
transmission line theory is based on analog analysis.

>'Just ones and zeroes' can be more than enough of a barrier. Just try
>to design anything with more than a few states. There are issues of
>state machine minimization, race and hazard detection and elimination,
                             ^^^^^^^^^^^^^^^^^^^^^^^^^
>and verification which have nothing to do with analog signals, per se.

I should have thought that race and hazard conditions are the
outworking of "analog" processes within the "digital" gates.
The bottom line is that when you look at things fast enough you'll
find a world where signals take whole ranges of values, regardless
of whether the circuit is nominally "digital". I think the original
posters comments about the world >30Mhz are quite valid.

gja