Modbus Function Codes - GE PACSystems RXi User Manual

8.5.6

Modbus Function Codes

This section summarizes the mapping of PACSystems reference tables to Modbus addresses
by the Modbus function codes supported by the Modbus TCP Server. The mapping shown in
this table assumes that the RXi Controller is configured to use its default reference table
sizes.
Modbus Function Code
1 Read Coils
5 Write Single Coil
15 Write Multiple Coils
2 Read Discrete Inputs
3 Read Holding Registers
6 Write Single Register
16 Write Multiple Registers
22 Mask Write Register
23 Read/Write Multiple Registers
4 Read Input Registers
7 Read Exception Status
8 Diagnostics
20 Read File Record
21 Write File Record
GFK-2816F
Chapter 8. Gigabit Ethernet (GbE) Interface Overview and Operation
Modbus
Start
Table
Address
0xxxx 1
1xxxx 1
4xxxx 1
3xxxx 1
n/a N/a
6yxxxx 1
August 2015
RXi Controller
Start
Length Length
Address
32768 %Q00001 32768
32768 %I00001 32768
1024 %R00001 1024
64 %AI00001 64
n/a n/a n/a
0 %W00001 0
149