I am trying to simulate the attatched code for pic18f550 in proteus.Pin 20 of the port D is supposed to toggle after some time delay.Now when I try to simulate, proteus gives an error related to clock frequency, which can be set in the edit dialogue box. Now,i don't know much about configuration bits(just started learning pic18) and I suspect it has some thing to do with the configuration bits and I have to set stuff accordingly in proteus. Please help me. It would be great if you could suggest some easy to use and free simulator for pic 18f. Thank you very much.