I was browsing the list and came across this question:

>Using the 12C67x part and observing the File Register Window I cannot see any
>change in the GPIO register when I do the following;
>Why wouldn't the FRW show my update GPIO?


The MPLAB simulator, while it works nicely (IMHO) is just a tab finiky and
VERY particular. (But we want it to be particular, yes?) In this instance,
it is slightly violating the 12C67X spec, but in an acceptable way I
believe. What it needs to work correctly is the ADCON wordcontrolling pin
useage to set pins to be digital pins, not analog A/D sources. Once this
change is loaded into the ADCON register the GPIO pins will read correctly.

Note in the real part if you use a pin for digital I/O and read it with the
D/A you will read your logic level in volts. (Or the spec says this, I
never tried it)

(This very problem stoped me cold for a day on a 12C671 project recently)