From dakott@alpha.delta.edu  Wed Jul  1 05:33:51 1998
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From: David Kott <dakott@alpha.delta.edu>
Sender: dakott@kott.my.domain
To: brian-c@technologist.com
Cc: handyboard@media.mit.edu
Subject: Re: microcontroller
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On Mon, 29 Jun 1998 brian-c@technologist.com wrote:

> -I'd like to say thanks to all the folks who replied
> to my question on the microcontroller speeds.
> 
> Here's another general question about them though.
> Should any unused pins be left open or should they 
> be grounded?
> 

Eeeeeeeeeeek!  Outputs left floating, CMOS inputs taken to ground with a
4.7K resistor... presuming, of course, that a Logic 0 on that input won't
generate adverse effects, e.g. a grounded active low interrupt line
might be a problem.  Such inputs should be taken to +5 with a 4.7K
resistor.

Floating CMOS inputs have a tendency to oscillate with the merest whisper
of a voltage.

TTL inputs may be left floating.

Driving an output externally will just heat up your CPU.. or worse.

							-d

-- 
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