Modbus TCP Explicit Messaging Request Codes

Overview

You can execute Modbus TCP explicit messages using either a Control Expert SEND_REQ function block or the Control Expert Ethernet Configuration Tool’s Modbus Explicit Message Window.

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

Request Codes

The following SEND_REQ function bloc request codes are supported by Control Expert for Modbus TCP explicit messaging:

Function Code		Description
Hex	Dec	Description
E	14	CIP request
50	80	Generic Modbus request, for example: write registers read holding registers
51	81	Read Holding Registers Modbus request
52	82	Write Multiple Registers Modbus request