Thanks for the info David.  After reading further it became clear that =
the "set to output" was the most common response.

I am a newbie and having fun learning a lot about the PIC and the 8051 =
at the same time.  Building two proto-types one for each controller and =
the engineering team will decide later which is better for our =
application.  My take is it will come down to cost and maintainability.

Regardless...  Sure am having a lot of fun.  My past life I was a Z-80 =
dude but things have certainly changed!!!

Thanks again for the answer and I'll have lots more stupid newbie =
questions but fortunately this list seems to deal with them very =
nicely!!!

Cheers,

Ken

-----Original Message-----
From: David Duffy [mailto:david@AUDIOVISUALDEVICES.COM.AU]
Sent: Thursday, August 29, 2002 4:19 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [PIC]: Unused pins


At 09:33 AM 29/08/02 -0500, you wrote:
>David,
>
>A newbie addition to this question.  What should the unused pins be =
"tied"
>to.  Ground???

Ken,
As previously advised, don't tie them to anything. Leave them not =
connected
& set as output.
This is not a "floating" pin as the PIC is driving the output to a known
state. The problem is
when the pin is set to *input* and left not connected. Then, external
forces (the way you hold
your tongue, phase of the moon, etc!) will let the pin wander into the
undefined region (neither
high nor low) and the PIC pin input circuitry will draw more current and
possible behave in a
less than predictable manner. As others have pointed out, if you have =
spare
port pins, you
can always add pull up/down resistors to them for future expansion. I =
hate
having PIC pins on
a board that are unused! I usually think of extra features to use them =
at
minimal cost or bring
them out to a connector (or pads) and chuck a series resistor in there =
(for
driving a LED) or
a pull-up resistor for adding a switch later on. A lot of the boards I
design are multi-purpose.
Regards...

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu