> Just laying out my first PIC PCB, and I was wondering what is the best 
> thing to do with any unused I/O pins? Tie to GND, +5V or leave 
> unconnected? />

Big ongoing discussions about this.
Much in archive.

Summary:

- Open inputs are very bad - avoid at all costs.
- Open outputs are fine BUT software glitches can set them to inputs and ...
- Inputs tied low or high can glitch to outputs and draw much current.
- Resetting pins to their intended states occasionally helps reduce above 
problems.
- Unless unused pin handling as above is well documented and rigorously 
followed it WILL catch you out sooner or later
- Best of all operationally is to tie to low or high with large value 
resistors. Best of all worlds. Pins can be used subsequently with ease. 
Provision of resistors is annoying and takes space.

No one solution works perfectly but some are better than others.


        RM
 

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