> "PORT does a read" ? So does doing BCF/BSF on LATx also.
> There is no difference in that way. BCF/BSF *always* reads.

My apology, I should have been specific and said "reads pins",
as I was thinking about r-m-w

>From DS70190C, Section 30.2 -

The differences between the PORTx and LATx registers can be
summarized as follows:

.. A write to the PORTx register writes the data value to the port latch.
.. A write to the LATx register writes the data value to the port latch.
.. A read of the PORTx register reads the data value on the I/O pin.
.. A read of the LATx register reads the data value held in the port latch.

Data on an I/O pin is accessed via a PORTx register. A read of the
PORTx register reads the value of the I/O pin, while a write to the
PORTx register writes the value to the port data latch. Many instructions,
such as the BSET and BCLR instructions, are read-modify-write
operations.

Therefore, a write to a port implies that the port pins are read, this valu=
e
is modified, and then it is written to the port data latch. Care should be
taken when read-modify-write commands are used on the PORTx registers
and when I/O pins associated with the port are configured as inputs. If an
I/O pin configured as an input is changed to an output at some later time,=
=20
an
unexpected value may be output on the I/O pin. This effect occurs because
the read-modify-write instruction reads the instantaneous value on the
input pin and loads that value into the port data latch.

[more about r-m-w]

The LATx register associated with an I/O pin eliminates the problems
that could occur with read-modify-write instructions. A read of the
LATx register returns the values held in the port output latches instead
of the values on the I/O pins. A read-modify-write operation on the LAT
register associated with an I/O port avoids the possibility of writing the
input pin values into the port latches. A write to the LATx register has
the same effect as a write to the PORTx register.

Joe

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