Typing Stateflow Data

What Is Data Type?

The term data type refers to the way computers represent numbers in memory. The type determines the amount of storage allocated to data, the method of encoding a data value as a pattern of binary digits, and the operations available for manipulating the data.

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Specifying Data Type and Mode

To specify the type of a Stateflow data object:

1. Open the Data properties dialog box, as described in Opening the Data Properties Dialog Box.

2. Select the Scope of the data object for which you want to set the data type.

   For more information, see Properties You Can Set in the General Pane.

3. Click the Data Type Assistant button.

   Note   If you know the specific data type you want to use, you can enter the data type directly in the Type field, or select it from the Type drop-down list, instead of using the Data Type Assistant. For more information, see Working with Data Types in the Simulink documentation.

4. Choose a Mode in the Data Type Assistant section of the dialog box.

   You can choose from these modes for each scope:

   Scope	Data Type Modes
   	Inherit	Built in	Fixed point	Enumerated	Expression	Bus Object
   Local		yes	yes	yes	yes	yes
   Constant		yes	yes		yes	yes
   Parameter	yes	yes	yes	yes	yes	yes
   Input	yes	yes	yes	yes	yes	yes
   Output	yes	yes	yes	yes	yes	yes
   Data Store Memory	yes

5. Based on the mode you select, specify a data type as follows:

   Mode	What To Specify
   Inherit	You cannot specify a value. You inherit the data type from previously defined data, based on the scope you select for the data object: If scope is Input, you inherit the data type from the Simulink input signal on the designated input port (see Sharing Output Data with Simulink). If scope is Output, you inherit the data type from the Simulink output signal on the designated output port (see Sharing Output Data with Simulink). Note   Avoid inheriting data types from output signals. See Avoid inheriting output data properties from Simulink blocks. If scope is Parameter, you inherit the data type from the associated parameter, which you can define in a Simulink model or the MATLAB workspace (see Sharing Inputs, Outputs, and Parameters with Simulink and the MATLAB Workspace). If scope is Data Store Memory, you inherit the data type from the Simulink data store to which you bind the data object (see Sharing Global Data with Multiple Charts).
   Built in	Select a data type from the drop-down list of supported data types, as described in Built-In Data Types.
   Fixed point	Specify the following information about the fixed-point data: Whether the data is signed or unsigned Word length Scaling mode For information on how to specify these fixed-point data properties, see Fixed-Point Data Properties.
   Enumerated	Specify the class name for the enumerated data type. For more information, see Using Enumerated Data in Stateflow Charts.
   Expression	Enter an expression that evaluates to a data type in the Type field. You can use these expressions: Alias type from the MATLAB workspace, as described in Typing Data by Using an Alias type operator to specify the type of previously defined data, as described in Deriving Data Types from Previously Defined Data fixdt function to create a Simulink.NumericType object that describes a fixed-point or floating-point data type For more information on how to build expressions in the Data properties dialog box, see Entering Expressions and Parameters for Data Properties.
   Bus object	In the Bus object field, enter the name of a Simulink.Bus object to associate with the Stateflow bus object structure. You must define the bus object in the base workspace. If you have not yet defined a bus object, click Edit to create or edit a bus object in the Bus Editor. Note   You can also inherit bus object properties from Simulink signals. See Using Composite Signals in the Simulink documentation. For more information about Stateflow bus object structures, see Working with Structures and Bus Signals in Stateflow Charts.

6. Click Apply to save the data type settings.

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Built-In Data Types

You can choose from these built-in data types:

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Inheriting Data Types from Simulink Objects

Stateflow data objects of scope Input, Output, Parameter, and Data Store Memory can inherit their data types from Simulink objects, as follows:

To configure these objects to inherit data types, create the corresponding objects in the Simulink model, and then select Inherit: Same as Simulink from the Type drop-down list in the Data properties dialog box. For more information, see Specifying Data Type and Mode.

To determine the data types that the objects inherit, build the Simulink model and look at the Compiled Type column for each Stateflow data object in the Model Explorer.

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Deriving Data Types from Previously Defined Data

You can use the type operator to derive data types from previously defined data. In the following example, the expression type(inbus) specifies the data type of the Stateflow structure counterbus_struct, where inbus is defined by the Simulink.Bus object COUNTERBUS. Therefore, the structure counterbus_struct also derives its data type from the bus object COUNTERBUS.

After you build your model, the Compiled Type column of the Model Explorer shows the type of each data object in the compiled simulation application. For more information, see type Operator.

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Typing Data by Using an Alias

You can specify the type of Stateflow data by using a Simulink data type alias (see Simulink.AliasType in the Simulink Reference documentation). Suppose that you define a data type alias named MyFloat as follows:

MyFloat = Simulink.AliasType;
MyFloat.BaseType = 'single';

In the following example, the data y has the same type as MyFloat.

After you build your model, the Compiled Type column of the Model Explorer shows the type used in the compiled simulation application.

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Strong Data Typing with Simulink I/O

By default, inputs to and outputs from Stateflow charts are of type double. Input signals from Simulink models convert to the type of the corresponding input data objects in Stateflow charts. Likewise, the data output objects convert to double before they are exported as output signals to Simulink models.

To interface directly with signals of data types other than double without the need for conversion, select Use Strong Data Typing with Simulink I/O in the Chart properties dialog box (see Specifying Chart Properties). When you select this check box, the chart accepts input signals of any data type that Simulink supports, as long as the data type of the input signal matches the type of the corresponding Stateflow data object. Otherwise, you receive a type mismatch error.

Note   For fixed-point data, select Use Strong Data Typing with Simulink I/O to flag mismatches between input or output fixed-point data in Stateflow charts and their counterparts in Simulink models.

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Sharing Chart Data with External Modules

Sizing Stateflow Data

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