Working with States in Charts

Creating a State

You create states by drawing them in the editor for a particular chart (block). Follow these steps:

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.

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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 Encapsulate Modal Logic 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 of a chart. For example, moving a grouped state moves all substates and functions inside that state.

How to Group a State

You can group a state by right-clicking it and then selecting Make Contents > Grouped in the context menu. The state appears shaded in gray to indicate that it is now grouped.

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

You can ungroup a state by right-clicking it and then clearing Make Contents > Grouped in the context menu. The background of the state no longer appears gray.

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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 Decomposition context menu, and select 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 Decomposition context menu, and select 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:

1. Right-click the state and select Properties.

   The State properties dialog box appears. For descriptions of properties, see Properties You Can Set in the General Pane and Properties You Can Set in the Logging Pane.

2. Modify property settings and then 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

Properties You Can Set in the General Pane

The General pane of the State properties dialog box appears as shown.

You can set these properties in the General pane.

Properties You Can Set in the Logging Pane

The Logging pane of the State properties dialog box appears as shown.

You can set these properties in the Logging pane.

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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 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 during or du, 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 label. Each block specifies the action for a specific event or set of events, for example:

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

The execution of the actions you enter for a state is dependent only on their action type, and not the order in which you enter actions in the label. If you do not specify the action type explicitly for a statement, the chart treats that statement as an entry action.

Tip   You can also edit the label in 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 properties 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 Output Data with Simulink 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 an Empty State Chart

Working with Transitions in Charts

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