There is no definitive answer, though the general consensus is to make them
inputs and tie them high or low through a resister.  While they are high
impedance already, tying them directly to the power supply is generally a bad
idea, mainly because the chance of blowing up the chip with the wrong supply
increases, but also to reduce the already miniscule current consumption.

-Adam

Paul Reilly wrote:
>
> Hi,
>
> I'm using a PICF877 in a project. It's got more ports than you could
> shake a stick at. My question is do I need to worry about ports I'm not
> using? Presently my code initialses all the ports at the beginning,
> regardless of they're going to be used. It then sets unused ports as
> inputs, like so:
>
>         bcf     STATUS, RP0             ; \
>                 bcf     STATUS, RP1     ; / select bank 0
>                 clrf    PORTA           ; initialise PORTA
>                 clrf    PORTB           ; initialise PORTB
>                 clrf    PORTC           ; initialise PORTC
>                 clrf    PORTD           ; initialise PORTD
>                 clrf    PORTE           ; initialise PORTE
>
>                 movlw   B'11111111'     ; port C - not used
>                 movwf   TRISC           ; make all inputs
>
>                 etc
>
> Is this worth doing, or can I just ignore unused ports and not bother
> setting their TRIS bits? I was going to tie all unused to Vss.
>
> Paul
>
> --
> http://www.piclist.com hint: The PICList is archived three different
> ways.  See http://www.piclist.com/#archives for details.

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.