II.3.2. Untimed Petri Nets
The sequencing of the events is reduced to simply ordering their occurrences. The simulation runs by firing the transitions one-by-one, in accordance with the transition firing rule. The PN Toolbox stores all the enabled transitions in a MATLAB array but only one transition fires at a time. The function that returns the next transition to be fired makes the decision according to the priorities or probabilities assigned to conflicting transitions from the Modeling/Resolution for Conflicting Transitions command.
For the simulation modes Step and Run Slow, the Events counter in the Status Panel is indexing and the currently firing transition gets the red color (by default) or an arbitrary color (selected by the user from the option Simulation/Preferences). After it is fired, a transition returns to the background color.
The usage of the Scope and Diary facilities is not relevant for this type of PN.