piclist 2001\01\02\094747a >
Thread: Picky I/O
face BY : Michael Rigby-Jones email (remove spam text)

{Quote hidden}

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.

This problem has been the downfall of many an I2C routine, even the ones
that come with Hitechs PICC don't address the problem properly.



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