On Sat, 29 May 2010 11:41:28 -0400, "Xiao Xu" said:

> >        RA4 = 1;

You must have really bad luck. I am not sure on the 16F684, but pretty
much traditionally RA4 is an open-drain pin.

It is the one pin that is a problem for beginners.

For now, try  to use RA3, or RA2, or RA1, or RA0.

Not RA4 or RA5.

After you get it all working, check out the 16F684 datasheet for PORT A
and you will see that not all the pins on that port are identical, and
using them as outputs is special.

Cheerful regards,

Bob

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