Kinco CD3 Series - MODBUS RTU Protocol Details

Kinco FD3&CD3 User Manual
118
12.3 MODBUS RTU
The RS485 interface of FD2S Servo driver supports Modbus RTU protocol.
Modbus RTU protocol format
Start(No less than 3.5
characters of
messages interval)
Station
No.
Function
code
Data
CRC
1 Byte
1 Byte
N Bytes
2 Bytes
Function code of Modbus
0x03
：
Read data registers
Request format：
Station No.
Function
Code
High Byte of
Start
Address
Low Byte of
Start
Address
High byte of
Address
Length
(Word)
Low byte
of
Address
Length
(Word)
CRC
check
1 Byte
03
1 Byte
1 Byte
1 Byte
1 Byte
2 Bytes
Normal response format:
Station
No.
Function
Code
Return data
length(Bytes)
High byte of
Register 1
Low byte of
Register 1
…
CRC
check
1 Byte
03
1 Byte
1 Byte
1 Byte
…
2 Bytes
If there is error such as non-exist address,then it will return function code 0x81.
For example:Send message 01 03 32 00 00 02 CA B3
Meaning:
01： Station NO.
03
：
Function code:read data registers
32 00：Read address starting from 4x3200(Hex).This is the Modbus address corresponding to parameter“Status
word”(60410010)
00 02
：
Read 2 words of data
CA B3：CRC check.
0x06：Write single data register
Request format:
Station
No.
Functi
on
Code
High Byte of
Register
Low Byte of
Register
High byte of
writing value
Low byte of
writing value
CRC check
1 Byte
06
1 Byte
1 Byte
1 Byte
1 Byte
1 Bytes
Response format:If writing successful,then return the same message.
If there is error such as address over range,non-exist address and the address is read only,then it will return function
code 0x86.
For example:Send message 01 06 31 00 00 0F C7 32
Meaning: