Ken:

        Two things. I've been caught on both (at least once)...

(i) GP3 is input only. The only 'drive' capability it has is through an
internal ~470K pullup resistor if it's enabled.

(ii) The TOCS bit in the option register defaults to 1 on powerup, forcing
GP2 to be an input for timer0, overriding any selection you make in TRIS.
You have to initialize OPTION as well.

        Hope this helps.

        Jim


>Can anyone tell me why this does not work, I have a 508 configured for
>int RC osc and int Reset with NO WDT.
>
>temp            equ     0x1c    ;File reg for temp storage
>
>        ORG     0               ;set start of program to 000 hex
>        movwf   OSCCAL
>
>start
>        clrf    GPIO
>        movlw   B'000000'       ;set all bits output
>        tris    GPIO
>        clrf    temp
>start2
>        incf    temp
>        movf    temp,w
>        movwf   GPIO
>        goto    start2          ;go and do it all again
>
>        END
>
>This gives the expected square wave output on GP0, GP1, GP4, GP5 but
>there is no outputs on GP2 and GP3. I have come to this simple loop
>because the main program that I have working in a 508 with XT osc stops
>working when I try and use the int RC osc.
>
>Ken.