crc校验算法（CRC check algorithm）.docVIP

crc校验算法（CRC check algorithm） CRC check and its algorithm The CRC algorithm has been mature and have a ready-made code so we can use the classic. CRC can be calculated by special hardware to achieve, but low-cost micro controller system, in the absence of hardware support under CRC test, the key issue is how to accomplish through software CRC calculation, CRC algorithm is the problem. The basic idea of CRC calibration using linear encoding theory, at the sending end according to the transmitted K binary code sequence, a check with supervision code with certain rules (CRC code) r, and attached to the information behind, constitute a new binary code sequence number (k+r) is a finally, send out. At the receiving end, according to the information between the code and the CRC code that follow the rules for inspection, to determine whether the error in transmission. 1. generation polynomial. The 16 bit CRC code generation rule is binary sequence to be transmitted first number 16 (both multiplied by the left shift ), divided by a polynomial, the remainder is finally obtained by CRC code. By an arbitrary binary string consisting of code and a polynomial coefficient is only 0 and 1 value of the corresponding. For example: polynomial code 1010111 corresponds to x6+x4+x2+x+1, and the polynomial is x5+x3+x2+x+1 corresponding code 101111. The standard CRC polynomial as follows: The name of the polynomial type short * standard reference CRC-4 x4+x+1 3 ITU G.704 CRC-8 x8+x5+x4+1 0x31 CRC-8 x8+x2+x1+1 0x07 CRC-8 x8+x6+x4+x3+x2+x1 0x5E CRC-12 x12+x11+x3+x+1 80F CRC-16 x16+x15+x2+1 8005 IBM SDLC CRC16-CCITT x16+x12+x5+1 1021 ISO HDLC, ITU X.25, V.34/V.41/V.42, PPP-FCS CRC-32 +x2+x+1 04C11DB7 ZIP, x32+x26+x23+... RAR, IEEE 802 LAN/FDDI, IEEE 1394, PPP-FCS CRC-32c x32+x28+x27+ +x8+x6+1 1EDC6F41 SCTP... Polynomial MSB fixed 1, so ignore the most high of 1 in the short type, such as 0x1021 is 0x11021. I, the basic algorithm (artificial Bisuan): Taking CRC16-CCITT as an example, the CRC ch