Stateflow®

Working with States in Stateflow^® Charts

Creating a State

You create states by drawing them in the Stateflow^® Editor for a particular Stateflow chart (block). The following is a depiction of the Stateflow Editor:

1. Select the State tool.

2. Move your pointer into the drawing area.

   In the drawing area, the pointer becomes state-shaped (rectangular with oval corners).

3. Click in a particular location to create a state.

   The created state appears with a question mark (?) label in its upper left-hand corner.

4. Click the question mark.

   A text cursor appears in place of the question mark.

5. Enter a name for the state and click outside of the state when finished.

The label for a state specifies its required name and optional actions. See Labeling States for more detail.

To delete a state, click it to select it and choose Cut from the Edit or any shortcut menu or press the Delete key.

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Moving and Resizing States

To move a state, do the following:

1. Click and drag the state.

2. Release it in a new position.

To resize a state, do the following:

1. Place your pointer over a corner of the state.

   When your pointer is over a corner, it appears as a double-ended arrow (PC only; pointer appearance varies with other platforms).

2. Click and drag the state's corner to resize the state and release the left mouse button.

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Creating Substates and Superstates

A substate is a state that can be active only when another state, called its parent, is active. States that have substates are known as superstates. To create a substate, click the State tool and drag a new state into the state you want to be the superstate. A Stateflow chart creates the substate in the specified parent state. You can nest states in this way to any depth. To change a substate's parentage, drag it from its current parent in the chart and drop it in its new parent.

Note   A parent state must be graphically large enough to accommodate all its substates. You might need to resize a parent state before dragging a new substate into it. You can bypass the need for a state of large graphical size by declaring a superstate to be a subchart. See Using Subcharts to Extend Charts for details.

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Grouping States

Grouping a state causes a Stateflow chart to treat the state and its contents as a graphical unit. This simplifies editing a chart. For example, moving a grouped state moves all its substates as well.

To group a state, double-click the state or its border.

The grouped state thickens its border and grays its contents to indicate that it is grouped.

You can also group a state by right-clicking it and then selecting Make Contents and then Grouped from the resulting shortcut menu.

You must ungroup a superstate to select objects within the superstate. To ungroup a state, double-click it or its border or select Ungrouped from the Make Contents shortcut menu.

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Specifying Substate Decomposition

You specify whether a superstate contains parallel (AND) states or exclusive (OR) states by setting its decomposition. A state whose substates are all active when it is active has parallel (AND) decomposition. A state in which only one substate is active when it is active has exclusive (OR) decomposition. An empty state's decomposition is exclusive.

To alter a state's decomposition, select the state, right-click to display the state's shortcut menu, and choose either Parallel (AND) or Exclusive (OR) from the menu.

You can also specify the state decomposition of a chart. In this case, the Stateflow chart treats its top-level states as substates. The chart creates states with exclusive decomposition. To specify a chart's decomposition, deselect any selected objects, right-click to display the chart's shortcut menu, and choose either Parallel (AND) or Exclusive (OR) from the menu.

The appearance of a superstate's substates indicates the superstate's decomposition. Exclusive substates have solid borders, parallel substates, dashed borders. A parallel substate also contains a number in its upper right corner. The number indicates the activation order of the substate relative to its sibling substates.

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Specifying Activation Order for Parallel States

You specify the activation order of parallel states by arranging them from top to bottom and left to right. A Stateflow chart activates the states in the order in which you arrange them. In particular, a top-level parallel state activates before all the states whose top edges reside at a lower level in the chart. A top-level parallel state also activates before any other state that resides to the right of it at the same vertical level in the chart. The same top to bottom, left to right activation order applies to parallel substates of a state.

Note   A Stateflow chart displays the activation order of a parallel state in its upper right corner.

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Changing State Properties

Use the State dialog box to view and change the properties for a state. To access the State dialog for a particular state, do the following:

1. Right-click the state.

   A shortcut pop-up menu appears.

2. Choose Properties from the shortcut menu.

   The State dialog for the state appears as shown.

   

The State dialog contains the following properties for a state:

3. After making changes, select one of these options:

• Apply to save the changes and keep the State dialog open.

• Cancel to return to the previous settings

• OK to save the changes and close the dialog box

• Help to display the documentation in an HTML browser window.

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Labeling States

The label for a state specifies its required name for the state and the optional actions executed when the state is entered, exited, or receives an event while it is active.

State labels have the following general format.

name/
entry:entry actions
during:during actions
exit:exit actions
bind:data and events
on event_name:on event_name actions

The italicized entries in this format have the following meanings:

Entering the Name

Initially, a state's label is empty. The Stateflow chart indicates this by displaying a ? in the state's label position (upper left corner). Begin labeling the state by entering a name for the state with the following steps:

1. Click the state.

   The state turns to its highlight color and a question mark character appears in the upper left-hand corner of the state.

2. Click the ? to edit the label.

   An editing cursor appears. You are now free to type a label.

   Enter the state's name in the first line of the state's label. Names are case sensitive. To avoid naming conflicts, do not assign the same name to sibling states. However, you can assign the same name to states that do not share the same parent.

   If you are finished labeling the state, click outside of the state. Otherwise, continue entering actions. To reedit the label, simply click the label text near the character position you want to edit.

Entering Actions

After entering the name of the state in the state's label, you can enter actions for any of the following action types:

• Entry Actions — begin on a new line with the keyword entry or en, followed by a colon, followed by one or more action statements on one or more lines. To separate multiple actions on the same line, use a comma or a semicolon.

  You can begin entry actions on the same line as the state's name. In this case, begin the entry action with a forward slash (/) instead of the entry keyword.

• Exit Actions — begin on a new line with the keyword exit or ex, followed by a colon, followed by one or more action statements on one or more lines. To separate multiple actions on the same line, use a comma or a semicolon.

• During Actions — begin on a new line with the keyword entry or en, followed by a colon, followed by one or more action statements on one or more lines. To separate multiple actions on the same line, use a comma or a semicolon.

• Bind Actions — begin on a new line with the keyword bind followed by a colon, followed by one or more data or events on one or more lines. To separate multiple actions on the same line, use a comma or a semicolon.

• On <event_name> Actions — begin with the keyword on, followed by a space and the name of an event, followed by a colon, followed by one or more action statements on one or more lines, for example

  on ev1: exit();
  

  To separate multiple actions on the same line, use a comma or a semicolon. If you want different events to trigger different actions, enter multiple on event_name blocks in the state's label, each specifying the action for a particular event or set of events, for example:

  on ev1: action1(); on ev2: action2();
  

  Note   The execution of the actions you enter for a state is dependent only on their action type, and not on the order in which you enter them in the label.

You can also edit the state's label through the properties dialog for the state. See Changing State Properties.

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Outputting State Activity to a Simulink^® Model

You can output the activity of a chart's states to a Simulink model via a data port on the state's Chart block. To enable output of a particular state's activity, first name the state (see Entering the Name), if unnamed, and then select the Output State Activity check box on the state's property dialog (see Changing State Properties). A data output port appears on the Chart block containing the state. The port has the same name as the state. During simulation of a model, the port outputs 1 at each time step in which the state is active; 0, otherwise. Attaching a scope to the port allows you to monitor a state's activity visually during the simulation. See Sharing Input and Output Data with Simulink^® Models for more information.

Note   If a chart has multiple states with the same name, only one of those states can output activity data. If you check the Output State Activity property for more than one state with the same name, the chart outputs data only from the first state whose Output State Activity property you specified.

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Creating a Stateflow® Chart

Working with Transitions in Stateflow® Charts