8 EtherNet/IP Communications
8 - 2
NX-series EtherNet/IP Coupler Unit User’s Manual (W536)
8-1 EtherNet/IP Functions
The EtherNet/IP Coupler Unit uses implicit and explicit message functions to exchange I/O data and
perform configuration settings. Connection-based cyclic, class 1, implicit messages are used to
exchange I/O information. Connection-based, class 3 explicit messages and connectionless UCMM
explicit messages are used for configuration and other non-cyclic communications.
Implicit communications allow cyclic communications (called tag data links in this manual) with Ether-
Net/IP devices. Data can be exchanged at high speed between EtherNet/IP Coupler Units and control-
lers using high-volume tag sets. Tag data links can operate at the cyclic period (cyclic communications)
specified for each application, regardless of the number of nodes. Data is exchanged over the network
at the refresh cycle set for each connection, so the communication’s refresh cycle will not increase
even if the number of nodes is increased, i.e., the synchronicity of the connection’s data is preserved.
Since the refresh cycle can be set for each connection, each application can communicate at its ideal
refresh cycle. For example, an application’s critical interlock information can be transferred at higher
speed while the less critical production commands and the status monitor information are transferred at
lower speed.
The communications load to the nodes must be within the Units’ allowed communication bandwidth.
There are 3 common types of implicit message connections classified as exclusive owner, input only
connection and listen only.
Exclusive Owner Connection
An exclusive owner connection uses a bidirectional connection with an EtherNet/IP slave that has
I/O data, to control output data to the EtherNet/IP slave where the data is controlled by only one Eth-
erNet/IP master, such as an EtherNet/IP Unit. You cannot make exclusive owner connections from
8-1-1 Implicit Message Communications
EtherNet/IP Unit
NX-series EtherNet/IP
Coupler Unit
EtherNet/IP port
EtherNet/IP Slave Terminal
Ethernet switch
Network Configurator
Implicit messages
Explicit messages
Explicit messages
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