If Proteus 8 stops with a fatal simulation error, don't worry — the issue is usually simple. Most of the time, the component you added requires a HEX file to simulate correctly. When this file is missing, Proteus can't run the internal behavior of that device, so the simulation fails.
This guide explains why these errors occur and shows exactly how to load the correct HEX file to get your simulation running again.
Why Fatal Simulation Errors Happen in Proteus 8
Certain parts used in Proteus aren't just symbols — they contain logic or firmware. Components such as IR receivers, microcontrollers, and smart modules depend on a HEX file to describe their behavior.
If this file is not assigned, Proteus has no instructions to follow, so the simulator stops immediately with errors like:
- Simulation aborted
- Device model missing program file
- Fatal simulation error
In short:
If a component performs processing or decision-making, it likely requires a HEX file.
The Role of HEX Files in Simulation
A HEX file is the compiled firmware of the part being simulated. For example:
- An IR module HEX contains code to decode infrared signals.
- A microcontroller HEX contains the uploaded program logic.
- Sensor models can use HEX to emulate internal timing and response.
Passive components (resistors, LEDs, switches) don't need HEX files — but active components do.
Before you start simulation, always confirm whether the device requires firmware.
How to Fix the Fatal Error (Step-by-Step)
Use the following steps to resolve the issue:
- Find the correct HEX file for the component you are using.
- Open your Proteus project.
- Double-click the component that triggered the error.
- Look for the section labeled Program File, HEX File, or Code File.
- Browse and select the HEX file.
- Confirm with OK, then run the simulation again.
If the HEX file matches the model, the simulation will run without errors.
Assigning the HEX File in Proteus
After opening the component properties window:
- The Program File field is usually found in the main tab.
- Select the file directly from your PC.
- If the option does not appear, that specific symbol is not a simulation model — choose an alternative component model from the Proteus library that supports firmware execution.
Example: Solving an IR Receiver Simulation Error
If you placed an IR receiver (such as TSOP1738 or VS1838) and the simulation crashes:
- Download a Proteus-compatible IR receiver HEX.
- Open properties by double-clicking the sensor.
- Assign the HEX file in the Program File section.
- Re-run the simulation.
The IR decoder will now respond to virtual remote input signals.
Where to Get HEX Files
You can obtain compatible HEX files from:
- The Proteus device library (often included)
- GitHub repositories with Proteus examples
- Arduino IDE output files (compile your own code)
To export your own HEX file in Arduino IDE:
File → Preferences → Enable "Show verbose output during compilation"
When compiling, the HEX file path will appear in the log.
Common Mistakes to Avoid
| Mistake | Result |
|---|---|
| Using the wrong HEX file model | Incorrect behavior or new errors |
| Moving the HEX file after linking | Broken file path errors |
| Forgetting to assign the HEX in component settings | Simulation won't execute |
Confusing .hex with library (.lib, .idx) files |
Component won't run |
Prevent Future Simulation Errors
- Keep a dedicated folder for HEX files used in projects.
- Add components one at a time, test, then continue.
- Choose components in Proteus marked SIM or ACTIVE MODEL.
Works for More Than IR Sensors
This same fix applies to:
- Ultrasonic sensors (HC-SR04)
- Microcontroller boards (Arduino, PIC, AVR)
- RFID scanners
- Bluetooth or WiFi modules with firmware
Any device needing internal logic must have a HEX assigned.
Final Notes
Fatal simulation errors in Proteus are usually resolved simply by assigning the required HEX file to the component. Once the correct firmware is linked, the simulation runs smoothly.
Run your circuit again — it should now work as expected.
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