5. Evolution rules

The GRAFCET evolution rules are the application, to the steps, of the principle of evolution between situations in the sequential part of the system.

In a grafcet, several steps can be active simultaneously, the situation then being characterized by the set of steps active at the moment in question. The conditions of evolution from one set of stages to another are then carried by one or more transitions, each characterized by: its upstream stages, its downstream stages, and its associated receptivity.