Why can’t I access my AOI local tags from my HMI?

A client contacted me this week with a problem. He couldn’t get his HMI to communicate to his ControlLogix AOI’s local tags.

However, what really seemed weird was that Rockwell HMI projects could do just this. So the question became, what trick was the factory using to make this possible?

I was fairly confident that referencing AOI local tags was do-able, but I thought I remembered there was some setting somewhere to enable it.

After hunting around in the software for awhile, I found the AOI Parameters and Local Tags screen did indeed have some advanced columns that were not displayed by default.

And the column and setting that I was confident was the culprit, external access, defaulted to off.

I selected it so it would be displayed, and found was the Rockwell example had the local tags set to “read/write,” while the clients had defaulted to “none.”

At this point it was as simple as changing the external access property from “none” to “Read/Write” and the HMI was now able to access the AOI’s local tags.

I hope you’ve found this article about accessing AOI local tags helpful.

If you have a comment or question, please feel free to share it with us by clicking on the “post a comment or question” link below.

Until next time, Peace ✌️ 

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Shawn M Tierney
Technology Enthusiast & Content Creator

Eliminate commercials and gain access to my weekly full length hands-on, news, and Q&A sessions by becoming a member at The Automation Blog or on YouTube. You'll also find all of my affordable PLC, HMI, and SCADA courses at TheAutomationSchool.com.

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Shawn Tierney

I'm a lifelong Technology Enthusiast who started programing in the early 80's on the new Apple II and VIC-20 personal computers. After earning a degree in Electronics, I worked as a Certified Automation Specialist for 25 years before leaving to focus on teaching at The Automation School, as well as publishing industry news and product how-to’s at The Automation Blog.

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