RMC EtherNet/IP Settings Page

To access the EtherNet/IP Settings page:
In the Project pane, expand the Modules folder, double-click the CPU module and click EtherNet/IP.

Use this page to configure the RMC's EtherNet/IP I/O settings.

Note: For the RMC200, in order to communicate via EtherNet/IP I/O, the Ethernet Protocol Mode must be set to EtherNet/IP. This setting is on the Ethernet Settings Page.

I/O Connection Settings

The RMC75E and RMC150E support a single EtherNet/IP I/O connection. The RMC200 supports up to 3 EtherNet/IP I/O connections to provide for more data. Which connections are used is defined when configuring the EtherNet/IP I/O connection in the PLC.

For each I/O connection, select the location in the RMC of the cyclic EtherNet/IP I/O data that will be sent between the RMC and PLC. Typically, you will choose this location from the Indirect Data Map. This section defines the starting addresses of the outgoing and incoming data. The length of the data is specified when configuring the EtherNet/IP I/O connection in the PLC.

The Outgoing Data is sent out by the RMC to the PLC and will appear in the PLC as Input Data.

The Incoming Data is sent out by the PLC (as its Output Data) and comes into the RMC.

Sync Register

For each connection, choose whether to use a Sync Register in the cyclic I/O data. The Sync Register provides a means for the PLC to synchronize the incoming data and the outgoing data.

For more details, see the Using an EtherNet/IP I/O Connection topic.

Logix Designer Export

The Export to Logix Designer button will start the wizard for exporting EtherNet/IP data communication tags and synchronization logic to a Rockwell Software Logix Designer .L5K file. For more details, see Using Logix Designer Export Components.

Quality of Service (QoS)

Quality-of-Service (QoS) allows Ethernet switches to prioritize EtherNet/IP packets to provide higher levels of determinism. EtherNet/IP supports two types of priority marking: 802.1D/Q priority tagging and DSCP marking. RMC75/150 controllers require firmware 3.41.0 or newer to support this feature. Only DSCP marking is enabled by default.

Changes to the QoS settings require restarting the controller to take effect.

802.1D/Q Priority Tagging

When enabled, the RMC tags outgoing EtherNet/IP packets with 802.1Q tags with priority 5 for I/O packets and priority 3 for all non-I/O EtherNet/IP packets. When disabled, no 802.1Q tags are applied. This feature is disabled by default because some devices and switches discard packets with 802.1Q tags. Therefore, it is important to properly design and test any system that will use 802.1D/Q priority tagging.

DiffServ Code Point (DSCP) Marking

When enabled, the RMC uses DSCP value 47 for I/O packets, and 27 for all non-I/O EtherNet/IP packets. When disabled, the DSCP field will always be 0. This feature is enabled by default.

Connection Problems with Older Rockwell Automation Ethernet Modules

Some Rockwell Automation Ethernet modules with older firmware incorrectly handle the default QoS object behavior of marking I/O data with non-zero DSCP values, causing the EtherNet/IP I/O connection to time out with error code 16#0203 shortly after it is established. Rockwell has a knowledge base article that discusses the issue (#63904 - https://rockwellautomation.custhelp.com/app/answers/detail/a_id/63904/). For the 1756-ENBT, this problem was fixed in revision 4.5.1.

To resolve this problem, Rockwell recommends upgrading the firmware in the affected Rockwell Ethernet module. If this is not possible, you can uncheck the Enable DiffServ Code Point (DSCP) Marking box in this section of RMCTools, which will resolve the problem.

For more details, see Troubleshooting EtherNet/IP I/O.

Encapsulation Inactivity Timeout

This feature causes the TCP connection used by EtherNet/IP messaging to close after the specified amount of time if there is no activity on the connection. The default timeout is set at 120 seconds. This default value can be used in most applications. However, this timeout is undesired in certain applications where the client does not make frequent requests, in which case the Encapsulation Inactivity Timeout should be disabled by setting it to zero.

Notice that RMCLink uses EtherNet/IP messaging and is affected by this timeout.

This feature is not supported on RMC75/150 controllers with firmware older than 3.62.0. To emulate pre-3.62.0 behavior, set this parameter to zero (0) to disable the feature.

Connection Problems with Older Rockwell Automation Ethernet Modules

With the Encapsulation Inactivity Timeout set to a non-zero value, older Allen-Bradley 1756-ENBT (prior to 4.007) and 1756-EN2T (prior to 1.004) Ethernet bridge modules will incorrectly close any EtherNet/IP I/O connection that was opened using the TCP/IP connection. This is seen in the RMC event log by the CIP IO connection timing out or being closed nearly exactly when the EtherNet/IP inactivity timeout occurs, which is also reported in the Event Log.

To resolve this problem, upgrade the firmware in the affected Rockwell module. If this is not possible, you can set the Timeout to 0. This disables the timeout, which will resolve the problem.

For more details, see Troubleshooting EtherNet/IP I/O.

Advanced Multicast I/O Connection Options

These options only apply when a multicast I/O connection is used. In most cases unicast I/O connections should be used. However, prior to RSLogix 5000 v18, Allen-Bradley PLCs only supported multicast I/O connections.

In RMC75/150 controllers with firmware prior to version 3.41.0, changes to these settings do not take effect until they are saved to Flash and the RMC is restarted. These settings are applied immediately for the RMC200 and RMC75/150 controllers with later firmware versions.

Multicast Address Range

For a multicast I/O connection, the RMC sends its produced data to a special multicast address rather than the IP address of a specific device. By default, the RMC selects a multicast address using an algorithm defined by the EtherNet/IP standard in the range of 239.192.1.0-239.192.128.224. However, if an IT manager requires that a different multicast address be used, then a specific range can be specified here. The RMC75/150 will use only the first address in the range specified. The RMC200 will use one of the first four addresses in the range specified.

Delta recommends that you leave this set to Obtain a multicast address using the default algorithm.

TTL Value

The Time To Live (TTL) setting specifies how far multicast I/O packets sent by the RMC can spread on the network. Each router (not switch) receiving the packet will subtract 1 from the TTL field prior to transmitting it. If the TTL field drops to zero, the packet is discarded.

In almost all cases, I/O devices and their controllers will be on the same network segment, separated only by switches and no routers. In this case, the TTL should be left at its default value of 1, ensuring that routers do not pass the multicast packets on to other networks. In the rare case where I/O traffic is to cross routers and span multiple network segments, then this value can be increased, but should only be done under the guidance of an IT professional.