JAJSP77A November 2019 – August 2020 BQ79600-Q1
PRODUCTION DATA
There are several methods for checking the CRC of a frame. One method is to simply calculate the CRC for the transmitted command except the last two bytes (CRC bytes) using the method described in the previous section, and then compare that result with the transmitted CRC bytes. A more simple option is to run the entire transmission through the CRC algorithm. If the CRC is correct, the result is 0000. In this case, the initial zero padding of the bit-stream with 16 zeroes is not necessary. Using the previous result and running through the algorithm produces the following results:
Example 1: CRC Verification Using Polynomial Division:
Command Frame = 0x80 00 02 0F 0B (0b1000 0000 0000 0000 0000 0010 0000 1111 0000 1011)
CRC to Check = 0xC029
Command Frame w/ CRC in bit stream order = 0x80 00 02 0F 0B C0 29 (0b1000 0000 0000 0000 0000 0010 0000 1111 0000 1011 0000 0011 1001 0100)
After Initialization (XOR with 0xFFFF) = 0b0 1111 1110 1111 1111 0100 0000 1111 0000 1101 0000 0000 0011 1001 0100
1111 1110 1111 1111 0100 0000 1111 0000 1101 0000 0000 0011 1001 010 #delete leading zeros from previous result
1100 0000 0000 0010 1 #XOR with polynomial
0011 1110 1111 1101 1100 0000 1111 0000 1101 0000 0000 0011 1001 0100
11 1110 1111 1101 1100 0000 1111 0000 1101 0000 0000 0011 1001 0100 #delete leading zeros from previous result
11 0000 0000 0000 101 #XOR with polynomial
00 1110 1111 1101 0110 0000 1111 0000 1101 0000 0000 0011 1001 0100
……
……
……
1100 0110 0000 0010 1001 0100
1100 0000 0000 0010 1 #XOR with polynomial
0000 0110 0000 0000 0001 0100
1 1000 0000 0000 0101 00
1 1000 0000 0000 0101 #XOR with polynomial
0 0000 0000 0000 0000 00
0x0000 #verfiy that CRC checks out valid
The result of ‘0b0000 0000 0000 0000’ for the CRC indicates a successful check.