Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!cs.utexas.edu!sdd.hp.com!horizon!kevin
From: kevin@horizon.COM (Kevin Criqui)
Newsgroups: sci.electronics
Subject: Advice needed on wire-wrapping CPU based circuits
Keywords: wire-wrap advice needed
Message-ID: <409@horizon.COM>
Date: 30 Aug 90 22:13:43 GMT
Organization: Science Horizons Inc. - Encinitas, CA
Lines: 23


I'm in the process of prototyping a small computer with a MC68000, some
EPROM, a duart and (hopefully), 8 megs of DRAM.  I've wire-wrapped the
circuit on a piece of perf board.  In trying to get the DRAM controller
working, I found that the 8 MHz system clock is quite noisy.  In fact,
if I look closely on the scope, I can see an occasional pulse of 2-2.5
volts during the time when the clock should be low.  The logic analyzer
confirms this, showing occasional glitches on the clock line.  I'm
fairly certain these glitches are causing the troubles I'm having with
the DRAM controller (a National Semiconductor 8421A).

I've tried beefing up the power and gound lines and have made sure
there are 0.1 uF bypass caps on all the chips with almost no luck.
Does anyone out there have any advice for me?  If you've successfully
wire wrapped a CPU based circuit that ran at 8 MHz (or higher), I'd
like to hear how you did it.

	_kevin

   |  Kevin Criqui                           kevin@horizon.com  |
   |  Science Horizons, Inc.           ...hp-sdd!horizon!kevin  | 
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