> Does anybody have information as to how to calculate this checksum? The details of the official checksum algorithm for each device is given in the "programming specificiation". That is a separate document from the data sheet. I also sorta remember you can import a HEX file into MPLAB and it can tell you the checksum it found. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body