In today's article (and video) I walk through how to add Ethernet Flex I/O to a ControlLogix System:

Step 1) To start, open your RSLogix 5000 or Studio 5000 project and find your Ethernet communications module under I/O Configuration. Once you find it, expand it by clicking on the plus sign (+) so you can see the “Ethernet” network under it:

NOTE: While some CompactLogix and ControlLogix controllers have Ethernet port(s) built-in, most will require you to add one to your project before you can add Distributed Ethernet I/O like Flex I/O.

Step 2) Next, right click on “Ethernet” and select “New Module”:

NOTE: While you may be tempted to try to add or “Discover” Flex I/O “Online,” this is not supported as shown below:

Step 3) In the “Select Module Type” window type in the part number of your Flex I/O Ethernet Adapter. In this example I'm using a 1794-AENT:

Step 4) Next, select your Adapter from the list and click on “Create”:

Step 5) In the “New Module” window, check the default “Revision” and “Chassis Size” to see if they match your actual Adapter and application. If not, click on “Change” to edit either or both fields:

Note: If your Adapter is already powered and wired to the network, you can check it's revision by first finding it in RSLinx, and then right clicking on it and selecting “Device Properties”:

Step 6) If you need to make a change, click on the “Change” button and update the “Revision” and/or the “Chassis Size” to match what you have installed and click on “OK.” Note that most Flex I/O Adapters support up to 8 modules, which is a chassis size of 8:

Step 7) After your Module Definition matches your physical hardware, you need to “Name” your adapter and give it an “Ethernet Address” before clicking on “OK”:

NOTE: It's important to understand that your Flex I/O Tags will show in Controller Tags using the name you give your adapter here. In our example we used the name “EFIO.”

Step 8) Once you're finished adding all your Ethernet devices, click on “Close”:

Step 9) With your Flex I/O Ethernet Adapter added to the I/O Configuration, the next step is to add your Flex I/O Modules to the Adapter. To do this, right click on the Adapter and select “New Module”:

Step 10) Now find and “Create” each of the Flex I/O modules connected to the Adapter:

Step 11) Just like with the Adapter, you can also find a module's “Revision” in RSLinx Classic by right clicking on the module and selecting “Device Properties”:

Step 12) As you add each module, confirm the “Module Definition” and “Slot” is correct before clicking on “OK”:

Step 13) Once all your modules have been added, you'll find their I/O Tags in Controller Tags with the “Name” you gave your Flex I/O Adapter.

In this case we used “EFIO” as our adapter's name, and below you can see our new “EFIO” Flex I/O Controller Tags:

The Automation Show, Episode 21:
Adding Ethernet Flex I/O To ControlLogix

I hope you found today's article (and video) about how to add Ethernet Flex I/O to your ControlLogix helpful!

If you have any comments or questions, please don't hesitate to post it using the “comment” link found below my signature.


Shawn Tierney
Automation Instructor and Blogger

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Shawn Tierney

Shawn began programming as a pre-teen in the early 80's, and later earned a degree in Electronics. He worked for 25 years as Automation Specialist, passionately sharing tech tips via his newsletter, then his BBS, before launching his first website in 1999. In 2013 he relaunched his website as, and now teaches full time at

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