Bernard, More info may be found on the use of the CCITT "HDLC" FCS/CRC in this RFC where they go into a little more detail *plus* they explain the use of their FCS generation code (as well as the complementing I mentioned previously): http://www.armware.dk/RFC/rfc/rfc1662.html See Appendix C first. This RFC is what did it for me ... Jim (seemingly ex-RF and now doing SW ...) ----- Original Message ----- From: "bernard wood" To: Sent: Saturday, July 28, 2001 6:02 AM Subject: [EE]: verify CRC-16 on "123456789" is BB3Dh?? Hi all, I've coded routines but need to verify that they do indeed produce the correct CRC. To do this, I need 2 known CRC check values. These are obtained by running thru the "standard" check string "123456789" of your algorithm and obtaining the result. I think that the check with CRC-16 on "123456789" is BB3Dh (can someone verify this?) Can someone (with known good code) please tell me what the 2 check CRC's are for both CRC-CCITT (x^16+x^12+x^5+1, or POLY=1021h) and CRC-16 (x^16+x^15+x^2+1, or POLY=8005h) or alternatively, send me known good code in C or VB6? Thanks in advance, Bernard Wood New Zealand -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.