Hi there, In addition to performing a multitude of other functions, I want to use 3-Pins of a PIC16F87X to monitor the presence and correct phase rotation (sequence) of a 3-Phase supply. Has anybody on the list done this before? Is it best achieved with interrupts or simply as part of the main loop? Basically, I need to check for a zero cross in correct order and in a given period of time. I would also like the code to be "smart enough" to detect if it is sensing 50Hz or 60Hz and adjust itself accordingly. If anybody has done anything in this area, I would be glad to hear from them. Regards, Sean Alcorn -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads