A customer asked me a question this week about Add-On Instructions that I had not considered before. I’m still struggling to see how you might deploy it and would love your input.
Add-On Instructions can call other Add-On Instructions in their routines. In other words you can nest AOIs and you can nest them up to seven levels deep. For the official documentation on AOI usage look at Logix5000 Controllers Add-On Instructions (Publication 1756-PM010C-EN-P) in Rockwell Automation’s Literature Library and refer to page 22 for information on nesting. To quote the manual, “This provides the ability to design more modular code by creating simpler instructions that can be used to build more complex functionality by nesting instructions.”
If you are not familiar with AOIs you can find several examples in the Sample Code Library. There is also an Add_On_Instruction_Samples.acd program that gets installed with RSLogix 5000 that you can access from the start page under Controller Projects then Open Sample Project.
I just can’t really picture a situation where it would simplify code to use this nesting technique. If anyone wants to help educate me and the rest of the readers please comment below or shoot me an email with a RSLogix 5000 project using this technique if you like. I will append this post with the advice.