Hi John, another thing to check out is your ADCON1 setting. It should be set to 0x07 - PORTA all digital. Otherwise analog pin, which has trisa set to output, will read zero no matter what you write to the pin. This will mess your signals during read-modify-write instructions (bsf porta,x bcf porta,x andwf porta,f...). Shared upper 16 bytes should also be considered, if you have some buffers addressed indirectly, the compiler may not catch it. Josef >>This may be a stupid question, so bear with me. Using a code set using PIC >>C for the C63 if recompiled for the F876, will the F876 execute at the same >>speed as the 63 using the same clock. >> >>I've got some time sensitive code that acts quirky on the F876. ======================================================================= Electronical devices for chemical laboratory, custom electronics design ----------------------------------------------------------------------- Snail Instruments Josef Hanzal, M. S. Vojanova 615 phone/fax: +420-311-24433 266 01 Beroun e-mail: snail@iol.cz Czech Republic URL: http://www.vitrum.cz/snail/ GPS: 49¡58'28" North, 14¡ 4'35" East =======================================================================