MODBUS Protocol
Function Codes
C-6 42i Low Source Instruction Manual Thermo Electron Corporation
*N = Quantity of Registers
Here is an example of a request to read registers 10–13:
The contents of register 10 are shown as the two byte values of 0x02 0x2B.
The contents of registers 11–13 are 0x00 0x00, 0x00 0x64 and 0x00 0x64,
respectively.
Response
Function code 1 Byte 0x03 or 0x04
Byte count 1 Byte 2 x N*
Register value N* x 2 Bytes
n = N or N+1
Error Response
Function code 1 Byte Function code + 0x80
Exception code 1 Byte 01=Illegal Function, 02=Illegal Address,
03=Illegal Data, 04=Slave Device Failure
Request
Field Name (Hex)
Function 0x03
Starting Address Hi 0x00
Starting Address Lo 0x09
No. of Registers Hi 0x00
No. of Registers Lo 0x04
Response
Field Name (Hex)
Function 0x03
Byte Count 0x06
Register value Hi (10) 0x02
Register value Lo (10) 0x2B
Register value Hi (11) 0x00
Register value Lo (11) 0x00
Register value Hi (12) 0x00
Register value Lo (12) 0x64
Register value Hi (13) 0x00
Register value Lo (13) 0x64
To Next Page
Loading...
