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Disclaimer: This document is written in the hope that you can utilize for your own education to gain knowledge of PLC systems (should you decide to utilize this document). Although I believe the information in this document to be accurate, it is YOUR responsibility to verify this information before implementing it in any way, especially when damage to personnel or equipment could result. By continuing to read this document, you agree to hold no one who writes, modifies, or distributes this document liable in any way (even negligence). Due to the wide variety of plant applications, some of the examples in this document may be prohibited at your location, or could cause damage to equipment, or harm personnel.
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Author: Ricky Bryce (Montgomery County, IL)
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Adding Ladder Logic Offline


  1. To add logic, we first have to get a new rung. You cannot add any logic to the END rung. For this example, we will use the drag and drop method for adding a new rung to ladder 2. Click on the “New Rung” icon, and drag the new rung down into the ladder view. You will see a red square. Move close to the red square, and it will turn green. Now you can drop the new rung.







  1. The first instruction we will discuss is the XIC instruction (Examine if Closed). The XIC instruction is looking for the value of 1 at a specific address in order to have logical continuity. Drag the XIC instruction onto your new rung.





  1. The next instruction we will place on the rung is the OTE instruction (Output To Energize) The OTE instruction writes a 1 to it's address when the rung is true, and a 0 to it's address when the rung is false.



  1. Now, you will notice the “?” above the instructions. This is because we have not addressed the instructions yet. Remember the input and output data tables? Ladder logic reads from these tables, and manipulates the data in these tables. Open the input data table. Recall that when you was online, and toggled switch 0 on and off, I:2.0/0 is the address that changed it's value. This is the address we will have the XIC instruction look at. Open the input data table, and drag the address of your first switch onto the XIC instruction. Remember you MUST see a green box before dropping the address on the instruction.





  1. Let's do the same thing with the output table. Drag O:3.0/0 onto the OTE instruction from the output data table.




  1. When you are finished, download and test your work. If your logic is working properly, when you throw switch 0, light 0 should energize automatically.



  1. Try adding the following rung of logic on your own. When you are finished download and test your work. We'll use the same switch, but a different light. This time we will be using the XIO instruction, which requires the switch to be off for the rung to be true.