Ladder Logic
Simulator

A ladder logic simulator is software that executes PLC programs without a physical PLC. Instead of downloading your program to a real ControlLogix or CompactLogix controller and connecting switches and sensors, you run the logic inside a virtual environment on your computer.

Why use a simulator?

• Test without hardware: Verify your logic works before deploying to production equipment.
• Training and learning: Understand how a program behaves by executing it step-by-step and watching tag values.
• Troubleshooting: Isolate logic errors without needing physical I/O or a connected PLC.
• No expensive tools: Eliminates the need for Logix Emulate ($2,000+) or dedicated hardware.
• Instant feedback: Toggle inputs in the browser and see outputs respond immediately.

The plc.company simulator reads your real ACD or L5X program and executes it exactly as a physical PLC would — same instruction set, same tag behavior, same timing logic.

1. Upload your file: Select your ACD (Allen-Bradley ControlLogix/CompactLogix project) or L5X (Logix Designer XML export).

2. Simulator parses your actual program: We read your real ladder logic, all your tags, data types, and timer/counter logic. This is not a generic demo — it is your program.

3. Toggle inputs: Use the browser interface to set digital input tags (I:0/0, I:1/5, etc.) to ON or OFF, just as if you had wired switches to the PLC.

4. Simulation executes: The simulator runs your ladder logic rungs in order. Each rung evaluates its conditions (XIC, XIO) and executes its outputs (OTE, OTL, OTU). Timers and counters accumulate in real time.

5. Watch window displays live values: Monitor any tag as the simulation runs. See outputs change as inputs toggle. View timer accumulate values, counter presets and accumulators, and any intermediate tag states.

6. Step or run continuously: Execute rung-by-rung to understand logic flow, or let the simulation run at full speed. Pause and inspect state at any moment.

The plc.company simulator executes the core ladder logic instruction set:

Digital Logic: XIC (Examine If Closed), XIO (Examine If Open), OTE (Output Energize), OTL (Output Latch), OTU (Output Unlatch), BJT (Branch Jump to Subroutine), BRK (Branch), etc.

Timers: TON (Timer On Delay), TOF (Timer Off Delay), RTO (Retentive Timer On). Timers accumulate in real time and control their done, timing, and enabled bits.

Counters: CTU (Count Up), CTD (Count Down), RES (Reset). Counters track preset, accumulator, underflow, overflow, and done bits.

Comparisons and moves: EQU (Equal), NEQ (Not Equal), LES (Less Than), GRT (Greater Than), MOV (Move), etc. Tag values flow through your logic.

Limitations: Physical I/O (analog input modules, network cards), motion instructions (servo, stepper), safety instructions, and network communication (EtherNet/IP, DH+) cannot be simulated — they are external to the controller's logic.

No. They are very different tools:

Logix Emulate is Rockwell Automation's official hardware emulation product. It is an industrial-grade tool designed to replace a real ControlLogix or CompactLogix chassis on a production network. It connects via EtherNet/IP, runs your actual firmware, and can communicate with real HMI systems, SCADA, MES platforms, and other enterprise tools. It costs approximately $2,000+ per seat and requires installation.

plc.company Simulator is a software-based ladder logic executor that runs in your web browser. It is designed for:

• Logic verification and testing before hardware deployment
• Training and operator familiarization
• Understanding unfamiliar programs
• Troubleshooting logic offline

Our simulator does not aim to replace Logix Emulate for production integration. If you need your simulated controller to communicate with HMI, SCADA, or other networked systems, Logix Emulate is the right tool. If you need to test logic quickly and learn how your program works, plc.company is free and instant.

The plc.company simulator is ideal for operator training and teaching engineers how a control system works:

Step 1: Load a real program. Upload the ACD file from your production system. You will immediately see all programs, rungs, and tags.

Step 2: Read the AI explanation. Our AI reads each rung and explains what it does in plain English. Understand the purpose without knowing every instruction name.

Step 3: Toggle inputs and watch outputs respond. Set a digital input (like I:0/0 for "Start Button") to ON. Watch the corresponding outputs, timers, and counters change. Repeat with different input combinations to understand the logic flow.

Step 4: Step through rungs one at a time. Execute rung-by-rung to see exactly when outputs turn ON, when timers start, and when jumps occur. Ideal for slow, detailed learning.

This method teaches operators how the actual system behaves without risking safety-critical equipment. For more structured training resources, check out our PLC operator training guide.

The plc.company simulator requires no Studio 5000 license, no Logix Designer, no Rockwell software, and no VPN access to your manufacturing network.

All you need: Your ACD or L5X file. If you have the project, upload it. If you do not, ask your plant engineer or IT team for an export.

To get an L5X export from Studio 5000: File → Export... → Select a program → Choose XML format (L5X). Done. This export is read-only and does not require any special tools.

Once uploaded, you can simulate your program from any device with a web browser — laptop, tablet, even a phone. No installation, no licensing, no setup.

For a detailed guide on opening ACD and L5X files, see our pages on ACD files and L5X files.