Thermo Scientific 410i Instruction Manual page 303

Function Code
Error Check
Function Codes
(0x01/0x02) Read
Coils/Read Inputs
Thermo Fisher Scientific
A slave address is not required in MODBUS over TCP/IP because the
higher-level protocols include device addressing. The unit identifier is not
used by the instrument.
The function code is a single byte in length. The following function codes
are supported by the instrument:
Read Coils
Read Inputs
Read Holding Registers
Read Input Registers
Force (Write) Single Coil
Read Exception Status
If a function code is received that is not in this list, an invalid function
exception is returned.
Data
The data field varies depending on the function. For more description of
these data fields, see "Function Codes" below.
In MODBUS over serial, an error check is included in the message. This is
not necessary in MODBUS over TCP/IP because the higher-level protocols
ensure error-free transmission. The error check is a two-byte (16 bit) CRC
value.
This section describes the various function codes that are supported by the
Model 410i.
Read Coils/Inputs read the status of the digital outputs (relays) in the
instrument. Issuing either of these function codes will generate the same
response.
These requests specify the starting address, i.e. the address of the first
output specified, and the number of outputs. The outputs are addressed
starting at zero. Therefore, outputs numbered 1–16 are addressed as 0–15.
: 0x01
: 0x02
: 0x03
: 0x04
: 0x05
: 0x06
Model 410i Instruction Manual
MODBUS Protocol
Function Codes
C-3