Learn more about Stateflow

Working with States in Charts

On this page…
Creating a State Moving and Resizing States Creating Substates and Superstates Grouping States Specifying Substate Decomposition Specifying Activation Order for Parallel States Changing State Properties Labeling States Outputting State Activity to a Simulink Model

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

When to Group a State

Group a state to move all graphical objects inside a state together. When you group a state, the chart treats the state and its contents as a single graphical unit. This behavior simplifies editing a chart. For example, moving a grouped state moves all substates and functions inside that state.

How to Group a State

To group a state, double-click the state or its border. The border of the state thickens and the background of the state appears gray to indicate that the state is grouped.

You can also group a state by right-clicking it and then selecting Make Contents > Grouped in the context menu.

When to Ungroup a State

You must ungroup a state before performing these actions:

• Selecting objects inside the state

• Moving other graphical objects into the state

  If you try to move objects such as states and graphical functions into a grouped state, you see an invalid intersection error message. Also, the objects with an invalid intersection have a red border.

  

How to Ungroup a State

To ungroup a state, double-click the state or its border. The border of the state thins and the background of the state no longer appears gray.

You can also ungroup a state by right-clicking it and then clearing Make Contents > Grouped in the context 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 can specify activation order by using one of two methods: explicit or implicit ordering.

• By default, when you create a new Stateflow chart, explicit ordering applies. In this case, you specify the activation order on a state-by-state basis.

• You can also override explicit ordering by letting the chart order parallel states based on location. This mode is known as implicit ordering.

For more information, see Explicit Ordering of Parallel States and Implicit Ordering of Parallel States.

Note   The activation order of a parallel state appears 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 box for a particular state:

1. Right-click the state and select Properties from the context menu.

   The State dialog box for the state appears as shown.

   

The State dialog box contains the following properties for a state:

Field	Description
Name	Stateflow chart name; read-only; click this hypertext link to bring the state to the foreground.
Breakpoints	Select the check boxes to set debugging breakpoints on the execution of state entry, during, or exit actions during simulation. See Debugging and Testing Stateflow Charts.
Function Inline Option	Select one of these options to control the inlining of state functions in generated code: Auto Inlines state functions based on an internal heuristic. Inline Always inlines state functions in the parent function, as long as the function is not part of a recursion. See What Happens When You Force Inlining. Function Creates separate static functions for each state. See What Happens When You Prevent Inlining. See Controlling Inlining of State Functions in Generated Code.
Test point	Select this check box to set the state as a test point that can be monitored with a floating scope during model simulation. You can also log test point values into MATLAB workspace objects. See Monitoring Test Points in Stateflow Charts.
Output State Activity	Select this check box to output the activity status of this state to a Simulink model via a data output port on the parent chart. See Outputting State Activity to a Simulink Model for more information.
Execution order	Set the execution order of a parallel (AND) state. This property does not appear for exclusive (OR) states. See Execution Order for Parallel States.
Label	The label for the state. This includes the name of the state and its associated actions. See Labeling States.
Description	Textual description or comment.
Document Link	Enter a URL address or a general MATLAB command. Examples are www.mathworks.com, mailto:email_address, and edit /spec/data/speed.txt.

2. After making changes, click one of these buttons:

   • Apply to save the changes and keep the State dialog box 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:

Keyword	Entry	Description
Not applicable	name	A unique reference to the state with optional slash
entry or en	entry actions	Actions executed when a particular state is entered as the result of a transition taken to that state
during or du	during actions	Actions that are executed when a state receives an event while it is active with no valid transition away from the state
exit or ex	exit actions	Actions executed when a state is exited as the result of a transition taken away from the state
bind	data or events	Binds the specified data or events to this state. Bound data can be changed only by this state or its children, but can be read by other states. Bound events can be broadcast only by this state or its children.
on	event_name and on event_name actions	A specified event and Actions executed when a state is active and the specified event event_name occurs See How Events Work in Stateflow Charts for information on defining and using events.

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 box 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 box (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 Charts

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