Newsgroups: comp.robotics
Path: brunix!sgiblab!swrinde!elroy.jpl.nasa.gov!news.claremont.edu!jarthur.claremont.edu!bgribble
From: bgribble@jarthur.claremont.edu (Bill Gribble)
Subject: Re: HC11 board design
Message-ID: <CDLxvr.Etv@news.claremont.edu>
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Organization: Harvey Mudd College, Claremont, CA 91711
References: <1993Sep19.135642.22263@newshub.ariel.yorku.ca>
Date: Sun, 19 Sep 1993 15:33:27 GMT
Lines: 18

In article <1993Sep19.135642.22263@newshub.ariel.yorku.ca> cs911225@ariel.yorku.ca (KEN E WILLMOTT) writes:
>Really? How did he get away without the extra 21 pullup resistors?
>Even if you had a way to eliminate the ones on port C, you'd have
>IC1, IC2, IC3, Rxd, MISO, the 10 meg across the xtal, STRA...
>etc. etc.

These are just not necessary (except for the 10M on the xtal).  It may be 
a loose design, but if the input capture, SCI, etc. systems are disabled
the inputs can do whatever they want.  In this case, they'll float high
anyway.  I've completed a number of 68HC11 designs where I eliminated these
pullups to save board space.  They worked fine, but in retrospect I 
would use a SIP resistor pack for the pullups, just so I could be happy
with the design.  

>	-Ken Willmott

Bill Gribble

