Appendix A
A-10 DVP-MC operating manual
Request message:
Field name Character
Start No input data for more than 10ms
Communication address 01
Function code 03
High byte of Modbus address 10
Low byte of Modbus address 00
Read high byte of data number 00
Read low byte of data number 02
Low byte of CRC check sum C0
High byte of CRC check sum CB
End No input data for more than 10ms
Response message:
Field name Character
Start No input data for more than 10ms
Communication address 01
Function code 03
Read data number(Counted by bytes) 04
Read high byte of data content 01
Read low byte of data content 00
Read high byte of data content 02
Read low byte of data content 00
Low byte of CRC check sum FA
High byte of CRC check sum AF
End No input data for more than 10ms
4. CRC check (check sum)
CRC check starts from “Communication address” to the last “Data content”. The calculation method is
shown below.
Step 1: Download a 16-bit hex register (CRC register) with the content value FFFF.
Step 2: Make the XOR operation between the 8-bit data of the first byte in the command and the 8-bit data
of the low byte in CRC register and then store the operation result in CRC register.
Step 3: Move the content value of CRC register by one bit towards the right and fill 0 in the highest bit.
Step 4: Check the value of the lowest bit in CRC register. If the value is 0, repeat the action of step 3; if 1,
make XOR operation between the content in CRC register and hex. A001 and then store the result
in CRC register.
Step 5: Repeat step 3 and step 4 till the content in CRC register is moved by 8 bits towards the right. At
this moment, the first byte of the command message is finished processing.
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