Modbus/TCP & Modbus RTU Function Codes
January 09 UDA2182 Communications User Guide 21
8. Modbus/TCP & Modbus RTU Function Codes
8.1 Function code definitions
The UDA Modbus protocol uses a subset of the standard Modbus function codes to provide access to
process-related information. These standard function codes provide basic support for IEEE 32-bit floating
point numbers, 32-bit unsigned/signed integer and 16-bit integer register representation of instrument’s
process data.
Repolling of data is not supported by this instrument.
Table 8-1 Modbus/TCP and Modbus RTU Function Codes Definitions
Function
Code
Name Usage Max. Number of
registers per transaction
03
Read Holding
Registers
Read data in 16-bit Register Format (high/low). Used to read
integer or floating point process data. Registers are
consecutive and are imaged from the instrument to the host.
120
04 Read Input
Registers
Provides Read access to any Analog Input Channel
positioned in any Rack or Slot.
120
16 (10h) Preset
Multiple
Registers
Write Data in 16-bit Format (high/low). Used to write integer
and floating point data. Registers are consecutive and are
imaged from the host to the instrument.
120
17 (11h) Report Device
ID
Read instrument ID and connection information, ROM
version, etc.
n/a
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