Getting strange PIC18F behavior? Try this.

[jtburnham]

We're using PIC18F2580s for our development project and were not able to get even the simplest Basic V2 examples to run correctly. The examples would run fine on 16F877A, but as soon as we moved to the 18F nothing would work.

After many hours with the datasheet that of course offered zero help, we thought we'd see if we could change any of the symptoms. Starting with the PICFlash, we changed the config bits one by one and reloading the PIC.

As soon as we disabled the Extended Instruction Set, the V2 example we had compiled started working. Testing with other examples also worked as expected and we've been able to get underway with the actual project.

So, if you're seeing strange behavior in your 18F that keeps sending you back to square one, try disabling the Extended Instruction Set (XINST in CONFIG4L) and reloading.

Jim Burnham