Operation Modes
Virtual PLC CPU operates under three distinct states. Each mode defines how the logic engine interacts with the project and the hardware.
Mode Definitions
| Mode | Status | Description |
|---|---|---|
| Stop | 🔴 Inactive | The PLC is idle and the logic program is loaded but not executed. |
| Run | 🟢 Active | The PLC is executing the logic program cyclically through the Scan Cycle. |
| Busy | 🟡 Processing | Active during program transfers. Automatically switches to Stop once the process finishes. |
The PLC Scan Cycle (Run Mode)
When the CPU is in Run Mode, it executes a repetitive process known as a Scan. This cycle is critical for ensuring real-time response and consists of the following phases:
- Input Status Update: The CPU reads the physical/virtual status of all inputs.
- Logic Execution: The application program is processed sequentially using the previously read input data.
- Diagnostics & Comm: The system performs internal integrity checks and manages communication tasks.
- Output Update: The results of the logic execution are written to the outputs, and the cycle restarts.
Cycle Time
The total duration of the scan depends on the program size, the number of I/Os, and the volume of communication required.
Busy Mode Behavior
This is a transient state. It is triggered exclusively when the EasyPLC Editor transfers a new logic program to the Virtual PLC CPU.
- During this state, the CPU is locked for writing.
- Once the transfer is successfully completed, the system defaults to Stop Mode for safety, awaiting a manual or commanded start.