So to convert back from 2's complement I need to: 1. Invert all the bits 2. Add 1 Is that right? Told you I should have gone back to bed! Thanks Graham -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads