Robert A. LaBudde says:

After considerable fooling around with this, I have now doped out the rules for using the MPSIM function in MPLAB:

1. No comments at top of .STI file.
2. Start first line with "CYCLE" followed by pin names.
3. Pin names are GP0-GP5 for 12C509A.
4. Save file as "name.STI".
5. Under OPTIONS|PROCESSOR SETUP|HARDWARE, set your configuration, regardless of any __CONFIG line in the assembler file. Only this option's settings will be used, including clock type and various enables.
6. Set DEBUG|STIMULATOR STIMULUS|PIN STIMULUS|ENABLE to the "name.STI" file used. ONLY the saved file will be used. Any open window with changes will be ignored. You must perform this function EVERY time the project is loaded. The setting is NOT saved!
7. Clear the StopWatch (WINDOW|STOPWATCH), or have it clear itself on reset.
8. Reset the simulator and step through the program.

If you do all of this, the simulator seems to work correctly. (Whew!)

It is annoying to have to assign the stimulus file each time the project is accessed, but I guess you can't have everything.

See also: