376
Table 12-2: Modbus RTU Function Codes Definitions
Function
Code
Name Usage
01 Read Coil
Status
Read the State of a Digital Output
02 Read Input
Status
Read the State of a Digital Input
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.
04 Read Input
Registers
06 Preset
Single
Register
Write Data in 16-bit Integer Format (high/low) ONLY.
08 Loopback
Test
Used for diagnostic testing of the communications port.
16 (10h) Preset
Multiple
Registers
Write Data in 16-bit Format (high/low). Used to write integer
and floating point override data. Registers are consecutive
and are imaged from the host to the instrument.
Note: UDC will write floating point data using this Function
Code.
17 (11h) Report
Device ID
Read instrument ID and connection information, ROM
version, etc.
For more information, see "Modbus RTU Function Codes" of 51-52-
25-66 Modbus RTU Serial Communications User Manual, which is
available at Honeywellprocess.com.
Chapter 12 - Standard Modbus Read, Write and Override Parameters
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