5.1 Data Format
5-3
● CRC-16 Calculation Example
Messages are processed one byte at a time in the work memory (a 16-
bit register known as the CRC register).
(1)The CRC register is initialized to H’FFFF.
(2)An XOR operation is performed on the content of the CRC register
and the first byte of the message, and the result is returned to the
CRC register.
(3)The MSB is packed with zeroes and the CRC register is shifted 1 bit
to the right.
(4)If the bit shifted from the LSB is 0, step 3 is repeated (next bit-shift
processing).
If the bit shifted from the LSB is 1, an XOR is performed on the
content of the CRC register and H’A001, and the result is returned to
the CRC register.
(5)Steps 3 and 4 are repeated until 8 bits are shifted.
(6)CRC processing continues to the end of the message, as XOR
operations are performed on the content of the CRC register and the
next byte of the message, step 3 is repeated, and the result is
returned to the CRC register.
(7)The result of the CRC calculation (value in the CRC register) is
appended to the last byte of the message.
Example of Appending the Calculation Result
When the calculated CRC value is H’1234, the CRC value is appended
to the command frame as follows.
CRC-16
11
Low
H'34
High
H'12
Data
CRC-16 calculation range
2 bytes
Slave
address
Function
code
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