Productivity PLC User Defined Instructions from AutomationDirect

AutomationDirect’s Productivity PLCs are powered by the Productivity Suite software — a tag-based ladder programming environment packed with advanced features and smart design tools. One of the most powerful of these tools is the User-Defined Instruction, or UDI. A UDI is like your own custom-built instruction — a modular, reusable block of logic that performs a specific control task. You can think of it as a self-contained mini program, complete with its own memory and input/output connections. If you’ve used Function Blocks or Add-On Instructions on other platforms, you already get the idea. It’s the same concept — reusable, organized code that keeps your programs clean, standardized, and scalable. And if you’re new to the idea, don’t worry — by the end of this video, you’ll see exactly how it works inside Productivity Suite, step by step. Let’s start simple. Imagine your project needs to perform the same mathematical calculation in several places. Rather than copying the same rungs of code over and over, you can build it once as a UDI and reuse it everywhere. To keep things easy to follow, we’ll make a UDI that just multiplies three numbers together — simple math, but a great way to show the process. First, let’s create a User-Defined Instruction. Having already created a new project in Productivity Suite version 4.5.0 or greater, open the UDI Management panel in the Tools menu from the menu bar. Before we create a new Instruction, let’s create a security key that we’ll be able to assign to it. Click the Security Key icon — it’s the fourth from the left — and in the Add UDI Security Key window, create a new one. We’ll call it “KeyA” with the tried-and-true password “guest123.” Next, click the Create New UDI button — that’s the leftmost icon — to open the Add UDI Definition window. Here, we’ll fill in the basic info: name, comment, revision, author, and so on. Let’s assign our KeyA security key while we’re here. Enter the password, and you’re ready to go. On the Properties tab, you’ll see the ID info we just entered. But the real action happens on the Ladder tab — this is where we’ll program the logic. Let’s drop in a Math instruction that multiplies our three values: Input1, Input2, and Constant. We’ll call the result Product. Variables like these that are used within the Instruction are called Parameters. For Data Type, we can just stick with 32-bit integer. For each of these, we can assign a default input value. The Scope column is where it gets interesting. In our example, Inputs 1 and 2 are going to be passed in from the program at large, so we need to choose “In.” The result, Product, will be passed out to the program and so has an “Out” scope. Constant is to be used only within the UDI, so it’s a “Local” variable. An In/Out tag could pass in either direction, but in this example, we don’t have any. Assignment is the process of linking program variables to instruction parameters, so that they can pass data back and forth, and different UDI instances may have their parameters linked to different program tags. “Assignment Required” means that the parameter must be explicitly assigned an external tag or value before the UDI will compile. When a parameter is marked as "Visible", it means that it can be seen on the UDI Instruction widget in a Task ladder editor. The Parameters tab shows all the parameter variables we just created. It would be possible to come to this tab first and create all of your parameters before writing your code on the ladder tab – it works either way. The Devices tab enables users to add a virtual hardware device that the instructions in the UDI definition ladder can reference. Before we deploy instances of this UDI, we should mention that there is another way to create these instructions. If you have an existing task that contains the logic you’ll need in a UDI, simply right-click on the task in the Task Management window and select “Create UDI Definition.” The Task logic will be duplicated in the ladder of a new UDI with the same name. Define your parameters as before. Now we’ve created an instruction. To deploy an instance of, or instantiate this instruction, close out of the UDI definition window and make your way back to the task where you’d like the instruction to be used. Click the far-right side of rung 1, and in the Instructions panel, expand the Program Control menu to find the User Defined Instruction. Double click. In the UDI window, drop down the UDI Definition menu and select the UDI we want to insert. Now you’ll see the instructions’ parameters listed Enter the tags to link to each of the parameters. Keeping things simple, we’ll say NumberA and NumberB are going to be passed into the parameters Input1 and Input2, respectively. The parameter Product will pass out to AnswerA. On the next rung, let's throw down another instance of the instruction. This time, we’ll pass NumberC to Input1, NumberD to Input2, and pass the Product out to AnswerB. Different iterations of the same code. Now, honestly, a simple arithmetic function like this isn’t the best use case for a UDI. In a more realistic situation, maybe you’re working with a system that monitors the levels in multiple liquid tanks of different sizes and shapes. Your UDI may become very complex, with logic for different tank geometries selected by a tank type input and tank measurement inputs, and multiple-level alarms/indications and pump/valve trigger outputs based on setpoint inputs or local parameters. The more duplicated code you can eliminate, the more UDIs really make sense. 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