Axcera 79XITS-7045 Benutzerhandbuch

WaveCom Electronics Inc

MA4040D Manual; MAN1L0901 REV 13(0104)

Approved: D.P.

36

The CRC calculations are performed using a table driven approach. The polynomial used is X^16+X^15+X^2+1.
Only the basic algorithm and lookup table will be described here. Refer to Appendix A for the CRC lookup table. 
Sample code is available on request. For further information, this approach is described in detail in the following
paper:

The algorithm for the CRC calculation is as follows:

Exclusive-OR the input byte with the low-order byte of the CRC register to get X.
Shift the CRC register 8 bits to the right.
Exclusive-OR the CRC register with the contents of the table, using X as an index.
Repeat steps 1 - 3 for all message bytes.

*

Note: The CRC register is 16 bits long, and should be cleared to 0 before beginning the
calculations.

For the transmit message: After all the message bytes have been processed, the CRC is tagged on to the end of
the message with the least significant byte first.
For the received message: After all the received message bytes have been processed, the resulting CRC should
be zero. If it is not zero, at least one bit error has occurred. If it is zero, it is assumed that no errors have occurred.