Thread Starter

Andrew Chiang

Hi All:

Can anyone tell me what is the standard used for CRC (Cyclic Redundancy Check) in BACnet PTP protocol ? My assumption is CRC-16. Is it correct?

Andrew ST Chiang
No. Annex G of the spec lays it all out for you. PTP specifies an 8 bit CRC on the header and a different, 16 bit CRC-CCITT on any data. The polynomials are G(X) = X to the eighth + X to the seventh + 1 for the header and G(X) = X to the sixteenth + X to the twelth + X to the fifth + 1 for any data.

B.O. Jan. 4, 2002
Robert Old
System Architecture
Siemens Building Technologies, Inc.
According to my copy of the standard, the header CRC uses one octet and the polynomial X8+X7+1, and the data CRC uses 2 octets and the CRC-CCITT polynomial X16+X12+X5+1.

Ken Irving