Stateflow

State Label Notation

The label for a state appears on the top left corner of the state rectangle with the following general format:

• name/
  entry:entry action
  during:during action
  exit:exit action
  on event_name:on event_name action
  

A state label starts with the name of the state followed by an optional / character (see State Name) and additional lines with keyword prefixes. Each keyword prefix identifies a different type of action associated with the state. These actions are as follows (short form is shown in bold):

Prefix	Action Type
entry	Entry action. See Entry Action.
during	During action. See During Action.
exit	Exit action. See Exit Action.
on event_name	Action occurring with event event_name. See On Event_Name Action.

You enter action statements for the state after the keyword label that identifies its type of action. Separate multiple actions for each action type with one of the following characters:

• Carriage return
• Semicolon
• Comma

You can specify multiple on event_name actions for different events by adding multiple on event_name lines specifying unique values for event_name.

Each keyword is optional and positionally independent. You can specify none, some, or all of them. The colon after each keyword is required. The slash following the state name is optional as long as it is followed by a carriage return.

If you enter the name and slash followed directly by actions, the actions are interpreted as entry action(s). This shorthand is useful if you are only specifying entry actions.

The action you specify in state labels forms a part of Stateflow action language. See Action Language.

State Label Example

The following example demonstrates the components of a state label.

State Name.   In this example, the state names are On and Off. The name of the state forms the first part of the state label. Valid state names consist of alphanumeric characters and can include the underscore (_) character, for example, Transmission or Green_on.

The use of hierarchy provides some flexibility in the naming of states. The name that you enter as part of the label must be unique when preceded by the hierarchy of its ancestor states. The name stored in the data dictionary is the text you enter as the label on the state, preceded by the hierarchy of its parent states separated by periods. Each state can have the same name appear in the label of the state, as long as their full names within the data dictionary are unique. Otherwise, the parser indicates an error.

The following example shows how hierarchy supports unique naming of states.

Each of these states has a unique name because of its location in the hierarchy of the Stateflow diagram. Although the name portion of the label on these states is not unique, when the hierarchy is prefixed to the name in the data dictionary, the result is unique. The full names for these states as seen in the data dictionary are as follows:

• Ride1.On
• Ride1.Off
• Ride2.On
• Ride2.Off

The following actions apply to the preceding State Label Example:

Entry Action.   State On has entry action on_count=0. The value of on_count is reset to 0 whenever state On's entry action is executed.

During Action.   State On has two during actions, light_on() and on_count++. These actions are executed whenever state On's during action is executed.

Exit Action.   State Off has the exit action light_off(). This action is executed whenever state Off's exit action is executed.

On Event_Name Action.   State On has on power_outage action. When the event power_outage occurs, the action handle_outage() is executed.

See Executing a State for information on how and when entry, during, exit, and on event_name actions are taken.

For more detailed information on the action language in transition labels, see Action Language.

State Decomposition

Transitions