More data = longer CRC

The probability of bit errors in a CAN FD frame increases compared to traditional CAN. This is the case because of the shorter bit times of Baudrate 2 on one hand and the much greater number of bits in the data field on the other. This needs to be countered by a larger redundancy in CAN FD frames. Otherwise the probability of errors remaining undetected by the receivers increases. CAN FD frames with data fields with up to 16 bytes will be secured by 17 CRC bits. Even larger data fields will cause the redundancy to have 21 bits.

The two generator polynomials are 0x3685B for CRC₁₇ and 0x302899 for CRC₂₁.