Glossary

The standard GRAFCET terms (IEC 60848) as used in GrafcetMaker.

Term	Meaning
Action	What the system does in relation to a step; drawn in a rectangle right of the step.
Active step	A step that is part of the current situation; it carries a token in simulation.
AND convergence	Double line where parallel branches end; the next transition waits for all of them.
AND divergence	Double line after a transition that activates several steps at once (parallel branches).
Assignment condition	Condition of a continuous action: the output is true only while the condition holds too.
Clear (a transition)	Cross it: activate the steps below, deactivate the steps above.
Clearable	Enabled and with a true receptivity: the transition will clear.
Continuous action	Output true while its step is active (and its condition is true).
Edge	Instant change of a signal: rising edge ↑a (false → true), falling edge ↓a (true → false).
Enabled transition	A transition whose upstream steps are all active.
Enclosing step	Step that contains an enclosed grafcet, which runs only while the step is active.
Event	An edge or other instant condition that triggers a stored action on event.
Expansion	The grafcet drawn for a macro-step, from its entry step E to its exit step S.
Forcing order	Action imposing a situation on another partial grafcet, e.g. `G2{8}`.
Initial step	Step active at start; drawn as a double square.
Macro-step	Step standing for an expansion drawn on its own sheet.
OR convergence	Single line where alternative branches join again.
OR divergence	Single line after a step followed by several transitions; one path is chosen.
Partial grafcet	One of the grafcets of a project; all run together.
Receptivity	The condition written next to a transition.
Search for stability	Repeating the evolution rules after an input change until no transition can clear.
Situation	The set of active steps at a given moment.
Source / sink transition	A transition with no step above it / below it.
Step	A stable situation of the system; drawn as a numbered square.
Step variable	`Xn`: true while step n is active.
Stored action	Action executed once — on activation, on deactivation or on an event — whose effect lasts.
Timer	`t/c`: true a time t after condition c became true, e.g. `5s/X2`.
Transient (unstable) step	Step activated and deactivated during one search for stability.
Transition	Bar between steps; the grafcet evolves by clearing transitions.