Delta Electronics Programmable Logic Controller DVP-PLC - Manual (Page 423)

8 Application Instructions API 100-149
DVP-PLC Application Manual 8-21
The operation of CRC checksum:
Step 1: Make the 16-bit register (CRC register) = FFFFH
Step 2: Exclusive OR the first 8-bit byte message instruction and the low-bit 16-bit CRC register. Store the
result in CRC register.
Step 3: Shift the CRC register one bit to the right and fill 0 in the higher bit.
Step 4: Check the value that shifts to the right. If it is 0, store the new value from Step 3 into the CRC register,
otherwise, Exclusive OR A001H and the CRC register, and store the result in the CRC register.
Step 5: Repeat Step 3 ~ 4 and finish calculating the 8 bits.
Step 6: Repeat Steps 2 ~ 5 for obtaining the next 8-bit message instruction until all the message instructions
are calculated. In the end, the obtained CRC register value is the CRC checksum. Be aware that
CRC checksum should be placed in the checksum of the message instruction.