Grafcet to STv1.0

Grafcet to ST v1.0

Draw several grafcets (IEC 60848), check their syntax and watch them live, scan by scan, like in a PLC.

Draw

Pick a tool, then click in a grafcet: Step, Initial step, Transition. With Link, click the source then the target (step → transition or transition → step). Select an element to edit it on the right; with a step selected, “＋ Transition + step” builds a sequence quickly. Drag to move, drag on the background to select several. Drag a segment of a link to move it; a double click on the link restores its automatic route.

Write

Receptivities in the usual notation: . AND, + OR, / NOT, ↑a ↓a edges (buttons, Alt+↑ / Alt+↓, or ^a), [c<4] comparison, 3s/X13 timer, 1 always true. A step is X12; if two grafcets have a step 12, write GA.X12. In a step label, / and . become _ (step 2/3 → X2_3).

Actions

Continuous, continuous with an assignment condition (drawn above the box), stored on event (flag: ↑sa while the step is active), each with an optional comment (tooltip, ST code), or stored on activation / deactivation (arrow above / below the box, as in the standard: C:=C+1).

Macro-step

Tool Macro: places M1 and opens its expansion G · M1, with an entry step E1 and an exit step S1; the steps 1.1, 1.2… belong to the grafcet. A transition above M1 activates E1, a transition below M1 is enabled by S1. XM1 is true while one step of the expansion is active. In simulation the symbol lights its top band (E1), its middle (inner steps) or its bottom band (S1). One level of macro-step only.

Force

On a step, “＋ Forcing order”: choose the grafcet and the order (several orders can share the double frame): situation G{8,9}, freeze G{*}, empty G{ }, initial G{INIT}. While the step is active, the forced grafcet cannot evolve; its actions go on. A grafcet is forced by one grafcet only, and never forces back. Hierarchy shows the levels; a forcing grafcet is evaluated before the grafcets it forces.

Variables

Declare inputs, outputs, internal variables and parameters, or click an unknown name to add it.

Check

Errors and warnings are listed live in Checks; a green ✓ in the title bar means the grafcet has no error.

Simulate

RUN, PAUSE, one Scan, Reset. Inputs: left click switches on / off, right click holds while pressed; click an enabled transition to fire it by hand. Each active step shows how long it has been active.

ST code

“ST code” shows the Structured Text written with the cf / X method: Header (declarations) and Body (code), each with Copy, or Export .txt for both. Forced grafcets get a _hold flag; forcing orders write their steps directly.

Files

Your work in progress is kept in this browser and comes back at your next visit (a tab closed by mistake); New starts again. It stays on this computer and is not a backup: use Save to keep your project (.json). PDF…: contents page with the hierarchy, variables, all grafcets at the same scale, and the ST code if you want it.

Evolution follows the method taught in class: all the firing conditions first (cf = upstream steps AND receptivity), then the steps (X = activation OR (X AND NOT deactivation)), one evolution per scan; grafcets from the highest level down (dashboard order on the same level), each one followed by its forcing orders, then timers, then actions. A step whose receptivity is already true stays active for one scan: the tool says so (in the standard, this transient evolution emits no continuous action).

On a phone: read, simulate and export; drawing needs a computer. Coming next: timing diagrams and a simulated process to test your grafcets. These tools are for learning and preparing: always validate your program in your PLC software (CODESYS…).

© 2026 Philippe RAYMOND · Licence CC BY-NC-ND 4.0
Official version: phil-legacy.github.io/toolbox