Simulation

The simulator runs your grafcet exactly according to the IEC 60848 rules, so you can test it before it reaches a PLC.

Start and stop

Press F5 (or Simulate › Start simulation). The diagram is locked, the simulation controls replace the tools at the top, the Simulation panel appears on the left (fold it with its chevron to see more of the diagram) and the clock starts running. Shift+F5 stops and returns to editing.

Change inputs

The Simulation panel lists the inputs:

• BOOL inputs have a switch, and a Hold button for a momentary press (like a push button; with the keyboard, hold Space on it).
• INT, REAL and TIME inputs have a value field.

You can also click a BOOL input where it is written in a receptivity or a condition on the diagram (tap it with a finger): it switches on or off. The grafcet evolves as soon as an input changes.

Point at a transition (or tap it) to see what it is waiting for: the steps that must be active first, or the terms of its receptivity that are still false, with the time left on a timer such as 10s/X0. An edge such as ↑start is always listed: it is only true at the moment its input changes.

Time

Time in the simulator is virtual and deterministic.

• F5 pauses the clock and runs it again. Timers (5s/X2) only advance while it runs.
• The speed goes from ×0.25 to ×10. Fast jumps straight from one timer expiry to the next.
• F10 jumps to the next timer expiry and runs that cycle.
• ⟲ restarts from the initial situation.

The bar shows the time, the cycle number and when the next timer expires. The default speed is in Settings › Simulation.

What you see on the diagram

• Active steps are filled and carry a token dot, with the time they have been active below.
• Enabled transitions have a ▶ marker; transitions flash when they clear.
• True signals are green, bold and underlined in receptivities and action conditions: a variable that is on, an active step Xn, a comparison that holds. What is not green is what the transition still waits for. Under a NOT bar the colour shows the signal itself: in /a, a is green when a is on.
• Continuous actions being executed show a ✓; stored actions show the current value of their variable.

Evolution log

The Simulation panel's log (folded: click Evolution log to open it) lists every cycle with what triggered it and each iteration of the search for stability: transitions cleared, steps activated and deactivated. Transient evolutions (steps crossed without stopping) are visible there. Click a cycle to see the diagram as it was at that moment.

Watching several grafcets

In a split view (Ctrl+\) both panes show the simulation live: watch a production grafcet and its safety grafcet, or a macro-step and its expansion, side by side.

Chronogram

The Chronogram tab draws every variable and the steps of the open grafcet over time. Click or drag in it to move back in time: the diagram follows. Back to live returns to the present.

Scenarios

To repeat a test exactly, record it:

1. Click Record: the simulation restarts and records every input change with its time.
2. Run your test, then stop the recording and name the scenario. It is saved in the project.
3. Replay restarts the simulation and plays the scenario back.

When the grafcet never settles

If transitions keep clearing each other (for example a loop where every receptivity is true), the evolution never becomes stable. The simulator stops after 1000 iterations and reports a transient loop in Problems. Add a condition (often an edge ↑a) so the loop cannot run forever. See Troubleshooting.