Thermo Scientific 48i Instruction Manual page 306

MODBUS Protocol
Function Codes
C-6 Model 48i Instruction Manual
Request
Function Code
Starting Address
Quantity of Registers
Response
Function Code
Byte Count
Register Value
*N = Quantity of Registers
Error Response
Function Code
Exception Code
Here is an example of a request and response to read registers 10–13:
Request
Field Name
Function
Starting Address Hi
Starting Address Lo
No. of Registers Hi
No. of Registers Lo
Response
Field Name
Function
Byte Count
Register Value Hi (10)
Register Value Lo (10)
Register Value Hi (11)
Register Value Lo (11)
1 Byte 0x03 or 0x04
2 Bytes 0x0000 to maximum allowed by instrument
2 Bytes 1 to maximum allowed by instrument
1 Byte 0x03 or 0x04
1 Byte 2 x N*
N* x 2 Bytes N = N or N+1
1 Byte Function code + 0x80
1 Byte 01=Illegal Function, 02=Illegal Address,
03=Illegal Data, 04=Slave Device Failure
(Hex)
0x03
0x00
0x09
0x00
0x04
(Hex)
0x03
0x06
0x02
0x2B
0x00
0x00
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