Explicit Messaging In Control Expert

Overview

This chapter describes how to execute in Control Expert using either:

the SEND_REQ function block
the Online Action window of the Control Expert EtherNet/IP configuration tool

Control Expert supports both and explicit messaging.

NOTE: Your Control Expert application can contain more than 16 explicit messaging blocks, but only 16 explicit messaging blocks can be active at the same time. Also, there can be only one concurrent explicit message - connected or unconnected - from an EtherNet/IP communication module to the same remote EtherNet/IP device.

What Is in This Chapter?

This chapter contains the following topics:

Explicit Messaging

TCP/IP-based messaging for Modbus TCP and EtherNet/IP. It is used for point-to-point, client/server messages that include both data—typically unscheduled information between a client and a server—and routing information. In EtherNet/IP, Explicit Messaging is considered Class 3 type messaging, and can be connection-based or connectionless.

connected messaging

In EtherNet/IP, connected messaging uses a CIP connection for communication. A connected message is a relationship between two or more application objects on different nodes. The connection establishes a virtual circuit in advance for a particular purpose, such as frequent explicit messages or real-time I/O data transfers.

unconnected messaging

In EtherNet/IP, unconnected messaging uses TCP (without a CIP connection) to send explicit messages. More overhead is contained within each unconnected message than for a connected message. The unconnected message is not necessarily provided destination node resources. Unconnected Messaging is used for non-periodic requests.