Simple XOR Circuit in Siemens TIA Portal V16 with PLC Sim

 Simple XOR Circuit in Siemens TIA Portal V16 with PLC Sim Public

Designing an XOR Gate Using Ladder Logic in Siemens TIA Portal

What is an XOR Gate?

An XOR gate gives a True (1) output only if one of the two inputs is True.

• If both inputs are False (0,0) → Output = False
• If first input is True, second is False (1,0) → Output = True
• If first input is False, second is True (0,1) → Output = True
• If both inputs are True (1,1) → Output = False

This makes the XOR gate slightly different from a standard OR gate, which is True if any input is True—even if both are.

---

Step 1: Translating XOR Logic to Ladder Contacts

To implement this in ladder logic, we can use a combination of Normally Open (NO) and Normally Closed (NC) contacts.

• For input A (I0.0), we’ll use an NO contact.
• For input B (I0.1), we’ll use an NC contact in parallel.
• Similarly, we’ll set the opposite condition in the second branch.

That means:

• Branch 1: A (NO) AND B (NC)
• Branch 2: A (NC) AND B (NO)

Both branches are placed in parallel so that the output is energized if either condition is satisfied.

The result: The output (Q0.0) is True only when exactly one input is True.

---

Step 2: Implementing in Siemens TIA Portal

1. Open TIA Portal and create a new project.
2. In Device Configuration, assign your CPU (e.g., Siemens S7-1200/1500).
3. In your main program block, start creating the ladder logic.
• Insert an NO contact for input A (I0.0).
• Insert an NC contact for input B (I0.1) in series to form the first branch.
• Open a parallel branch and build the second condition (A as NC, B as NO).
• Connect both branches to the output coil (Q0.0).
4. Download the program to your PLC.

---

Step 3: Using PLC SIM to provide user inputs

Setting Up PLC SIM (more info : TIA Portal: PLC Simulation (PLCSIM S7-1500))

 

PLC SIM SIM Table

---

 

Step 3: Testing the XOR Ladder Logic

Once the program is downloaded:

• Inputs (0,0): No signal passes → Output = Off
• Inputs (1,0): First branch passes → Output = On

 

• Inputs (0,1): Second branch passes → Output = On

• Inputs (1,1): Both branches are blocked → Output = Off

You can verify this using the monitoring tool in TIA Portal, where active logic paths are shown in green.

---

Step 4: Converting Ladder Logic to FBD

One of the great features of TIA Portal is that you can easily switch between Ladder Logic (LAD) and Function Block Diagram (FBD).

• Simply right-click your main program block and convert LAD to FBD.
• The XOR logic will automatically be generated in FBD form:
• It shows two AND blocks with inverted inputs, connected in parallel to an OR block.
• Download this FBD representation to your PLC, and the behavior will be identical.
• Inputs (0,0): No signal passes → Output = Off
• Inputs (1,0): First branch passes → Output = On

 

• Inputs (0,1): Second branch passes → Output = On

 

• Inputs (1,1): Both branches are blocked → Output = Off

 

 

---