I was under the impression that bsf and  bcf instructions are OK on a
Port as long as the I/O directions are not changed.
Example.

Port Status
TrisA = b'00000011'
PortA = b'00000000'  (Latch Value)
RA0 - driven high by external stimulus
RA1 - driven low by external stimulus

bsf porta,2

Reads porta data. = b'00000001'
Performs bit manipulation. = b'00000101'
Writes data to port. = b'00000101'  (Latch Value)

Read PortA. = b'00000101'

RA2 - RA7 are irrelevant as I am only interested in RA0 - RA1.

RA0 - still driven high by external stimulus.
RA1 - still driven low by external stimulus
Change TrisA register. = b'00000010'
RA0 - is now driving it's load with a high output.

This may be undesirable because the BSF instruction changed the value
in RA0 output latch from 0 to 1.

Therefore if I have used BSF and BCF instructions on a Port and decide to
change the I/O direction, I should set the Output Latches to a known state
beforehand.

movlw b'xxxxxxx0'  (x in this case is irrelevant).
movwf PortA

Then change RA0 to an output.

Tony





Just when I thought I knew it all,
I learned that I didn't.