Modbus TCP Explicit Messaging Function Codes

Overview

You can execute Modbus TCP explicit messages using either a Control Expert DATA_EXCH function block or the Modbus Explicit Message Window.

NOTE: Configuration edits made to an Ethernet module are not saved to the operating parameters stored in the CPU and, therefore, are not sent by the CPU to the module on startup.

Function Codes

The function codes supported by the Control Expert graphical user interface include the following standard explicit messaging functions:

Function Code (dec)	Description
1	Read bits (%M)
2	Read input bits (%I)
3	Read words (%MW)
4	Read input words (%IW)
15	Write bits (%M)
16	Write words (%MW)

NOTE: You can use the DATA_EXCH function block to execute any Modbus function, via program logic. Because the available function codes are too numerous to list here, refer instead to the Modbus IDA website for more information about these Modbus functions, at http://www.Modbus.org.