If you're going to configure RA4 as output, you should tie it up first to VDD
since it is open-collector. (Use pull-up resistor).

Werner Soekoe wrote:

> Hi
>
> I wonder if anyone could adivse me. I made a PIC16F84 circuit using all 13
> I/O pins to drive 13 LEDs, but the LED connected to RA4 doesn't light up. It
> appears that the pin does provide a signal, though. When I read up some more
> in the PIC16F84 datasheet, I came accross a paragraph which said that all RA
> pins are CMOS drivers, except RA4 which is an "open-drain" output. Is this
> why it can't deliver current? What does the "open-drain" mean?
>
> Thanks
>
> Werner Soekoe
> wsoekoe@global.co.za