What about Rockwell’s AOIs

These don’t seem like outlandish questions so why don’t we dive into the subject and see what happens? First of all, let me acknowledge that anyone interacting with the program whether that be a developer or maybe maintenance personnel, will have to spend a little time learning how to navigate among the UDT’s the AOD’s and finally the AOI’s. (We’ll sort out the alphabet soup in a little bit.) Let’s also discuss the need to properly validate an AOI.  You have to have tested the AOI thoroughly enough to trust that it reliably does the job for which it is intended. I think most users of the Rockwell Automation ControlLogix family of controllers are familiar with User Defined Types (data types or UDT’s).  It seems to be common practice for developers to define UDT’s to organize the properties associated with something that is repeatedly used within an application’s program such as locations or an ISA-88 unit or perhaps something as abstract as a ‘Finite State Machine’ module. AOD’s (Add On Defined) are a type of UDT where the developer sets up a data structure for …