Hey all,

I've been trying for a couple weeks to use the PORTC pins on a PIC 16F877
for output along with the hardware serial port. The hardware serial port
functions fine and I can communicate with another host unless the
following subroutine is called before the serial routines:

I8255WriteConfigRegister
; set address lines of the 8255 to access its config register
        movlw   b'00001111'
        movwf   PORTC
; load the config value and write it to the config register
        movf    I8255CONFIGVALUE, W
        movwf    PORTD
        call I8255WriteStrobe
        return

The serial port doesn't work if this routine is called as part of my
initialization code when my program first starts. Any idea what could be
causing this? I've read not to do read-modify-write instructions on TRISC
but I don't think I'm doing this, I'm just writing to PORTC. The complete
code can be found at http://www.geneseo.edu/~lkp3/cirtest.asm

It's basically some IDE interface code I am brewing up for the PIC that
uses an Intel 8255a to reduce the number of pin's the PIC needs for the
task. I saw the same concept used with another microcontroller and I'm
trying to adapt it to the pic. The code IDE interface code will be made
available freely once it's complete, as I couln't find anything equivalent
and free while googling around.

Lindsay

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