Delta Electronics DVP10MC11T — dVP-MC Operating Manual: Modbus Communication and CRC Check [294/375]

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.