Thermo Scientific Omni FTIR Multi Gas CEMS, Instruction Manual

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Modbus Protocol
Function Codes
B-4 Omni FTIR Multi Gas CEMS Instruction Manual Thermo Fisher Scientific
Request
Function Code 1 Byte 0x03
Starting Address 2 Bytes 0x0000 to maximum allowed by instrument
Quantity of Registers 2 Bytes 1 to maximum allowed by instrument
Response
Function Code 1 Byte 0x03
Byte Count 1 Byte 2 x N*
Register Value N* x 2 Bytes N = N or N+1
*N = Quantity of Registers
Here is an example of a request and response to read registers 9–12:
Request
Field Name (Hex)
Function 0x03
Starting Address Hi 0x00
Starting Address Lo 0x08
No. of Registers Hi 0x00
No. of Registers Lo 0x04
Response
Field Name (Hex)
Function 0x03
Byte Count 0x06
Register Value Hi (9) 0x02
Register Value Lo (9) 0x2B
Register Value Hi (10) 0x00
Register Value Lo (10) 0x00
Register Value Hi (11) 0x00
Register Value Lo (11) 0x64
Register Value Hi (12) 0x00
Register Value Lo (12) 0x64
The contents of register 9 are shown as the two byte values of 0x02 0x2B.
Then contents of registers 10–12 are 0x00 0x00, 0x00 0x64 and 0x00
0x64, respectively.