Network Communications
6
6.3 MEMOBUS/Modbus Communications
YASKAWA SIEPC71061737D GA800 Drive Technical Reference 319
Use this procedure to calculate CRC-16:
1. Make sure that the start value is FFFF (Hex.).
2. Calculate the FFFF (Hex.) start value and the XOR of the slave address (exclusive OR).
3. Move the step 2 results one column to the right. Do this shift until the carry bit is 1.
4. When the carry bit is 1, calculate XOR via the result from the above step 3 and A001 (Hex.).
5. Do steps 3 and 4 until the 8th shift to the right.
6. Use the result of step 5 to calculate the XOR and the data of the following messages (function code, register
address, data). Do steps 3 to 5 until the last data, then calculate.
7. The result of the last right shift or the value of the last XOR calculation is the result for CRC-16.
Table 6.6 lists examples of the CRC-16 calculation of slave address 02 (Hex.) and function code 03 (Hex.). The
calculated results of CRC-16 for this section is D140 (Hex.).
Note:
The calculation example only gives information about some error checks with CRC-16. The drive will do the same error checks for the next
data.
Table 6.6 CRC-16 Calculation Example
Description Calculation Overflow Description Calculation Overflow
Initial value (FFFF (Hex.)) 1111 1111 1111 1111 - Function code 03 (Hex.) 0000 0011 -
Address 02 (Hex.) 0000 0010 - XOR w result 1000 0001 0011 1101 -
XOR w initial value 1111 1111 1111 1101 Shift 1 0100 0000 1001 1110 1
Shift 1 0111 1111 1111 1110 1 XOR w A001 (Hex.) 1010 0000 0000 0001 -
XOR w A001 (Hex.) 1010 0000 0000 0001 - XOR result 1110 0000 1001 1111 -
XOR result 1101 1111 1111 1111 - Shift 2 0111 0000 0100 1111 1
Shift 2 0110 1111 1111 1111 1 XOR w A001 (Hex.) 1010 0000 0000 0001 -
XOR w A001 (Hex.) 1010 0000 0000 0001 - XOR result 1101 0000 0100 1110 -
XOR result 1100 1111 1111 1110 - Shift 3 0110 1000 0010 0111 0
Shift 3 0110 0111 1111 1111 0 Shift 4 0011 0100 0001 0011 1
Shift 4 0011 0011 1111 1111 1 XOR w A001 (Hex.) 1010 0000 0000 0001 -
XOR w A001 (Hex.) 1010 0000 0000 0001 - XOR result 1001 0100 0001 0010 -
XOR result 1001 0011 1111 1110 - Shift 5 0100 1010 0000 1001 0
Shift 5 0100 1001 1111 1111 0 Shift 6 0010 0101 0000 0100 1
Shift 6 0010 0100 1111 1111 1 XOR w A001 (Hex.) 1010 0000 0000 0001 -
XOR w A001 (Hex.) 1010 0000 0000 0001 - XOR result 1000 0101 0000 0101 -
XOR result 1000 0100 1111 1110 - Shift 7 0100 0010 1000 0010 1
Shift 7 0100 0010 0111 1111 0 XOR w A001 (Hex.) 1010 0000 0000 0001 -
Shift 8 0010 0001 0011 1111 1 XOR result 1110 0010 1000 0011 -
XOR w A001 (Hex.) 1010 0000 0000 0001 - Shift 8 0111 0001 0100 0001 1
XOR result 1000 0001 0011 1110 - XOR w A001 (Hex.) 1010 0000 0000 0001 -
Perform operations with next data (function code)
XOR result 1101 0001 0100 0000 -
CRC-16
1101 0001 0100 0000 -
D 1 4 0
(Lower) (Upper)
-
Continue from here with next data.
Response Data
The drive does the CRC-16 calculation for the response message and makes sure that the data does not have errors.
Make sure that the calculated value is the same value as the CRC-16 in the response message.
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