piclist 2001\01\02\104554a >
Thread: Picky I/O
www.piclist.com/techref/microchip/ios.htm?key=i%2Fo
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face BY : David VanHorn email (remove spam text)



>
>Umm..I don't think that statement is entirely accurate.  When the pin is
>switched to an output (by modifying the TRIS register), whatever is in the
>the port latch is output on the pin.  The critical point is that you cannot
>guarantee what is in the output latch if you have performed ANY Read Modify
>Write operations on the port latch since that pin was configured as an
>input.  The only safe ways this can be done is to either set the output
>latch once and never do any RMW operation on that port, which is a tad
>limiting, or explicitly set the the port latch every time before you clear
>the TRIS bit.

At this point, I'm ok.
I'm able to do BCF and BSF on the tris register, and on the port with
predictable results.

I had a couple problems hitting me at the same time, giving some pretty
wierd symptoms.

One point of note, I had missed that RA4 is open-drain, and therefore can't
drive high no matter WHAT you do in the code :)


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