Sometimes, as a reaction to external changes, the system is able to perform more than one step without additional external stimuli. Each step in such a series of steps, except for the initial one, is triggered by changes the system itself produced in the previous step. This chain of steps continues until the system reaches a status from which it cannot advance without further external input and/or without advancing the clock. Such a status is called a stable status. The progression from one stable status to another is called a Superstep.
● States S1 and S4 define a stable status since no change in the system status occurs without an external stimuli being introduced.
● Event E is generated.
● Event F is generated internally. This allows the simulation to take the transition from S5 to S6 without additional external stimuli.
● The resulting configuration, S2 and S6, is the next stable status. Without generating event G or advancing the clock at least 5 units, no transition takes place. Therefore the sequence of steps from states S1 to S2 and S6 is a superstep.