Motion iWMC Series - MODBUS RTU Communication; Function Code of Modbus

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6.3 MODBUS RTU Communicaon
The iWMC integrated servo wheel supports the MODBUS RTU communicaon protocol, and its internal object is a
disconnuous 16-bit data register (mapped to 4X when read and wrien by the host computer). Modbus RTU protocol
format:
Staon No.
Funcon code
Data
CRC
1 byte
1 byte
N bytes
2 bytes
6.4 Funcon Code of Modbus
⚫ Funcon code 0x03: read data registers Request format:
Staon No.
Funcon
code
Modbus address
Read the byte number
CRC
High byte
Low byte
High byte
Low byte
1 byte
03
1byte
1byte
1byte
1byte
2byte
Response format:
Staon No.
Funcon
code
Return data length
Register data
……
CRC
High byte
Low byte
1 byte
03
1 byte
1 byte
1 byte
……
2 bytes
Note
If there is error such as non-exist address, then it will return funcon code 0x81.
⚫ Funcon code 0x06: write single data register Request format:
Staon No.
Funcon
code
Modbus address
Wring value
CRC
High byte
Low byte
High byte
Low byte
1 byte
06
1 byte
1 byte
1 byte
1 byte
2 bytes
Response format: If wring successful, then return the same message.
Note
If there is error such as address over range, non-exist address and the address is read only, then
it will return funcon code 0x86.
⚫ Funcon code 0x10: Write mulple registers Request format:
Staon
No.
Funcon
code
Modbus
address
Data length (word)
Data
length of
data-in
Low byte of data
High byte of data
CR C
High
byte
Low
byte
High
byte
Low
byte
High
byte
Low
byte
1 byte
10
2 bytes
1 byte
1
byte
1 byte
1
byte
1
byte
1
byte
1
byte
2 bytes