Specifications

Optimizing Performance

EIO0000000051 6/2010

Message Connection Types

Introduction

The transmission of most messages require a point-to-point connection between a

transmitter and receiver.

For all types of explicit messages, the connection automatically closes when the

communication ends, or is timed-out.

For implicit messages, the connection must be kept open. If the I/O connection—CIP

for EtherNet/IP, TCP for Modbus TCP—the transmission stops. In this case, the

scanner employs the TCP implicit messaging connection to dynamically re-establish

the CIP connection.

Calculating the Connection Timeout

For CIP connections, you can control the connection timeout setting by specifying

both the network multiplier and the requested packet interval (RPI in ms):

Timeout = Network Multiplier x RPI

NOTE: You can locate and configure these values in the Unity Pro Ethernet

Configuration Tool. Open the DTM Editor for the Ethernet communication module,

then edit the following settings:

z the network multiple is the Time-out Multiplier parameter found in the

Device List → <device> → <connection> → Connection Settings page, and

z the RPI is the EM Connection RPI parameter found in the Channel Properties

→ EtherNet/IP page

A large timeout value may affect the ability of the network to optimize the availability

of connection resources, re-establish connections, and update I/O data when the

connection is lost.

A small timeout value may unnecessarily cause the frequent closing and re-

establishing of connections.

It is preferable to use a larger timeout value for explicit messaging connections, and

a smaller timeout value for implicit messaging connections. The specific value you

employ depends on your application requirements.