text: <s>[INST] Using AOIs in w/FTLogix Echo and Studio 5000 question. I have recently started testing my 5580 PLC logic using FTLogix Echo. I have some AOI logic that was previously developed by the client that gave us the go-by logic. My question is: Are AOIs emulated with FTLogix? What I noticed is that I couldn't get any values that were supposed to be written internally by the AOI logic to work, but if I tied those parameters to external variables and moved those around, THEN the logic would function. Say for example, I had some logic that would look at a 3-state switch and had an internal parameter called 3_switch. If I tried to write to that parameter (AOItest.3_switch) either with logic or by just clicking on the parameter and entering a value, I couldn't change the value. But, if I change the parameter to required in the Instruction Definitions and make a new external tag that is assigned to that parameter, the value will change when I change values in the newly created tag (newtag-->AOItest.3_switch). I just need to know if this is something I just need to deal with in testing or do I need to modify the AOIs/logic permanently. [/INST] I've been using Echo quite a bit recently.  Where I used to jump immediately to the controller on my desk, I prefer the speed and convenience of testing with Echo. Echo does indeed support add-on instructions.  And you should be able to feed (not required) input values into the add-on tag structure. When you feed data into the instruction through a required input parameter via an external tag as you suggest, that data is copied into the AOI tag structure immediately before executing the add-on logic.  (If it's an in/out parameter, the data isn't copied... the actual external tag is used directly by the addon.) In my experience, things like this tend to explained by something not-so-obvious.  For example: 1. Logic in the enable-in-false routine changes the value, 2. Logic in a separate task changes the value. Or even something as silly as a typo such that the data is fed into a tag structure that is not the same add-on tag as on the instruction faceplate.\n </s>