Thanks for your detailed reply, Henrik. In the past, I've just used a GOSUB in the main loop and in the subroutine call ADCIN and compare the current value to a previous value; if it's different, I use that 8-bit value to set a PWM duty cycle to brighten/dim an LED. For this project, I thought it might be more efficient to set up an AD_INT interrupt which I thought would be triggered whenever I turn the dial on the trim pot and hence slightly more efficient. I think I see now that I'm wrong in what I thought would trigger this interrupt and that I guess I have to go back to the GOSUB approach.