The PIC16C7X data sheet gives sample code for changing the prescaler assignment from the watchdog to timer0 and vice versa. In both cases, a literal is put into the W register and then moved to the OPTION register. Must it be done this way, or can a bit clear/set instruction be used instead to just clear/set the PSA bit? Keith Keith D. Kotay kotay@cs.dartmouth.edu http://www.cs.dartmouth.edu/~kotay