= CRC =
A cyclic redundancy check (CRC) is an error-detecting code.

http://en.wikipedia.org/wiki/Cyclic_redundancy_check
http://en.wikipedia.org/wiki/Computation_of_cyclic_redundancy_checks 

== HDLC like framing ==
The http://www.ietf.org/rfc/rfc1662.txt has two examples of CRC calculations.

Polynom CRC-16: 0x8408 ( CRC-16-CCITT Reversed )
Polynom: x^0^ + x^5^ + x^12^ + x^16^

== CRC-16-IBM ==
Bisync, Modbus, USB, ANSI X3.28, SIA DC-07, many others; also known as CRC-16 and CRC-16-ANSI

Polynom: x^16^ + x^15^ + x^2^ + 1

||Normal||Reversed||Reversed reciprocal||
||0x8005||0xA001||0xC002||