> if the port
> bit is held up, a byte is written to the whole port, and the bit in
> question just happens to be low.  Does the port bit input buffer go low
> momentarily, then get pulled back high again once the write operation is
> over?  If it doesn't then OK, but if it does, would that trigger an
> interrupt?

The output latch is set whenever a bit is written, but this is only used to
drive the pin if the bit is configured as an output.  Any read, which
includes lots of intructions you might not think of, will copy the value of
an input pin to the output latch, even though the bit wasn't "written" to.
This only matters when you are switching a pin from being an input to an
ouput.


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, olin@embedinc.com, http://www.embedinc.com

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads