Stateflow

Implicit Events

Stateflow defines and triggers the following events that typically occur whenever a chart executes:

• Chart waking up
• Entry into a state
• Exit from a state
• Value assigned to an internal (noninput) data object

These events are called implicit events because you do not have to define or trigger them explicitly. Implicit events are children of the chart in which they occur. Thus, they are visible only in the charts in which they occur.

Referencing Implicit Events

Action expressions can use the following syntax to reference implicit events.

• event(object)
  

where event is the name of the implicit event and object is the state or data in which the event occurred. Valid implicit event names (and their shortcuts) are wakeup (also referred to as tick), enter (en), exit (ex), and change (chg).

If more than one object has the same name, the event reference must qualify the object's name with that of its ancestor. The following are some examples of valid implicit event references.

• enter(switch_on)
  en(switch_on)
  change(engine.rpm)
  

Note    The wakeup ( or tick) event always refers to the chart of the action being evaluated. It cannot reference a different chart by argument.

This example illustrates use of an implicit enter event.

Fan and Heater are parallel (AND) superstates. By default, the first time the Stateflow diagram is awakened by an event, the states Fan.Off and Heater.Off become active. The first time event Fan_switch occurs, the transition from Fan.Off to Fan.On occurs. When Fan.On's entry action executes, an implicit local event is broadcast (i.e., en(Fan.On) == 1). This event broadcast triggers the transition from Heater.Off to Heater.On (triggered by the condition en(Fan.On). Similarly, when the system transitions from Fan.On to Fan.Off and the implicit local event Fan.Off is broadcast, the transition from Heater.On to Heater.Off is triggered.

Specifying Trigger Types

Defining Data