There are two schools of thought on this and there are valid reasons for
both. 
1. Pins to input and tied to a supply line. 
2. Pins to output with dummy data on them.

If the pins are inputs and tied then when you read the port as a whole you
will get some absolute data that can be checked against a reference so
therefore validating the input.

If the pins are outputs then there is always room for expansion / debugging
connections to other 'Stuff' and can be used on s future enhancement of the
product for zero cost.

Both have benefits the choice is bipolar...

Steve

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
Roger Weichert
Sent: 13 September 2009 05:04
To: Microcontroller discussion list - Public.
Subject: [PIC] Unused port lines question

Hi Guys,

I'm building a project (using a PIC16F627) and have reached the stage where 
I'm ready to design the board layout, so need to decide what I'm going to do

with the unused port lines. As you'll be able to see, I don't have a lot of 
experience.

RA0,1,2,3 are used as O/P's and RA4 unused . so can I leave RA4 as an output

and leave it unconnected .. or should it be terminated in some way?
RB0 is used for an EXT Int . RB1,2,3,4 as I/P's .. and RB5,6,7 unused.

I'm assuming I should leave RB5,6,7 as I/P's and just tie them directly to 
Vdd.

I'm aiming for a tiny pcb with no wasted space, so am trying to avoid any 
components I don't absolutely need to have.

Thanks for any advice.

Regards, Roger 

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