I need a XFP complient CRC code module. Or I need to validate the one that I got. So any help (pointers to code, pointers to XFP CRC spec, notes on how to validate) would help. Sean
"Now I did not create this table, I found it on a french site..." Something got muffed in the translation ;-) "...and just kept swapping tables (only once, i got lucky) until the validation results were there. The validation test must not have hit upon the one bad feedback table entry. "I got the original wrong table from either Kiel or Cygnal or maybe phillips." Actually, you probably got the right table from one of those locations -- right for Dallas One-Wire, that is. DOW does not use the same polynomial as the one you seem to need. So to be picky, you should probably remove the Dallas reference in your function's comment, lest it confuse someone down the road. The CRC/poly you are apparently needing is a common one found in a number of standards (e.g., IEEE 802.6-1990, ISO/IEC 13239) where 8-bit CRCs are used.