Data Structures and UDT in RSLogix 5000 PLC Programming

A key concept in PLC programming is data structures. They govern how data is captured by the inputs, processed by the PLC and is sent out to the outputs and field devices. A skilled PLC programmer is comfortable working with all of the data structures we will cover in this post. In addition to the base constructs, vendors (Allen Bradley, Siemens, Opto 22, and others) have created vendor defined data types that can be used in special applications. Examples include timers, counters, motion, and more. Lastly, we’ll dive into User-Defined Data Types, or UDTs; a way for the PLC programmer to create their own definition of a data structure. We’ll answer the why, how and when to use UDTs.

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