Rockwell Automation 1747-L55x,D174710.4 SLC 500 Ethernet - Manual (Page 31)

Chapter
4
Publication 1747-10.4
Communicating on the
Ethernet Network
This chapter:
•
describes how Ethernet connections are established
•
provides information on MSG instruction parameters, interpreting
MSG error codes, and interpreting Ethernet status data
•
explains how to use advanced Ethernet functions
TCP/IP is the mechanism used to transport Ethernet messages. On
top of TCP, the Client/Server Protocol is required to establish
connections and to send the MSG commands. Connections can be
initiated by either a client program (INTERCHANGE or RSLinx
application) or a processor.
The client program or processor must first establish a connection to
the SLC 5/05 to enable the SLC 5/05 to receive messages from a
client program or another processor. In order to send an outgoing
message, the SLC 5/05 must first establish a connection with the
destination node at a specified IP address on the Ethernet network.
A connection is established when a MSG instruction executes and no
previous connection to that particular Ethernet device exists.
When a MSG instruction executes, the SLC 5/05 checks to see
whether a connection was established with the destination IP
address. If a connection was not established, the SLC 5/05 attempts
to establish a connection.
In order to receive messages from another device on Ethernet, an
“incoming” connection must be established. This incoming
connection is made by the sending processor and uses one incoming
connection in the receiving processor.
The SLC 5/05 supports a maximum of 16 connections, allowing
simultaneous communication with up to 16 other devices or
applications. The connections are dedicated as follows:
Number of Connections Dedicated to:
4 outgoing messages
4 incoming messages
8 either incoming or outgoing messages
Important: For outgoing connections, no more that one connection
per destination IP address is established. If multiple
MSG instructions use the same destination IP address,
they share the same connection.
Ethernet Connections