User Defined Data Type [UDT] Tutorial - Explanation, Usage, Examples & Custom Definition in RSLogix 5000

User Defined Data Types or UDTs are commonly used in Programmable Logic Controller Programming in order to group data and maximize code reusability. This structure allows the user to combine any of the existing data types into a package which can be reapplied multiple types across the program, be exported and imported into other structures.

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Can you create UDT while online or does the PLC has to be offline just as the case for creating AOI?

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You can add UDTs online. However, you can’t make changes to them as freely as you can offline. For that reason, I always recommend creating them offline and importing them into a program (can be done online). Once in place, if you need to make changes, you must delete all instances of that UDT and re-import.

Hope that helps,

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