Hi, only for the sake of correctness: Port A, pin 4 makes no sense. Pin 4 is the MCLR pin of the said PIC. The correct wordness is Port A, bit 4 as John M. wrote. And it is the pin 3 of that PIC. Imre On Fri, 24 Jul 1998, Matt Bonner wrote: > Midgley John wrote: > > > > I'm struggling with some strange behaviour on an 'F84. Port A, > > pin 4 > > Go no further. As soon as I see a PortA question, I know that bit 4 is > going to be involved. Put a pull-up resistor on it - it's open drain. > > --Matt > >