You create function arguments for a MATLAB Function block by entering them in its function header in the MATLAB Function Block Editor. When you define arguments, the Simulink® software creates corresponding ports on the MATLAB Function block that you can attach to signals. You can select a data type mode for each argument that you define for a MATLAB Function block. Each data type mode presents its own set of options for selecting a data type.
By default, the data type mode for MATLAB Function block function arguments is Inherited. This means that the function argument inherits its data type from the incoming or outgoing signal. To override the default type, you first choose a data type mode and then select a data type based on the mode.
To specify the type of a MATLAB Function block function argument:
From the MATLAB Function Block Editor, select Edit Data to open the Ports and Data Manager.
In the left pane, select the argument of interest.
In the Data properties dialog box (right pane), click the Show data type assistant button to display the Data Type Assistant. Then, choose an option from the Mode drop-down menu.
The Data properties dialog box changes dynamically to display additional fields for specifying the data type associated with the mode.
Based on the mode you select, specify a desired data type:
|Mode||What to Specify|
|You cannot specify a value. The data type is inherited from
previously-defined data, based on the scope you selected for the MATLAB
Function block function argument:|
|Select from the drop-down list of supported data types, as described in Built-In Data Types for Arguments.|
Specify the fixed-point data properties as described in Specifying Fixed-Point Designer Data Properties.
|Enter an expression that evaluates to a data type, as described in Specifying Argument Types with Expressions.|
|In the Bus object field, enter the name
of a |
You can click the Edit button
to create or modify
|In the Enumerated field, enter the name of a |
MATLAB Function block function arguments can inherit their data types, including fixed point types, from the signals to which they are connected.
Select the argument of interest in the Ports and Data Manager
In the Data properties dialog,
Inherit: Same as Simulink from the Type drop-down menu.
See Built-In Data Types for Arguments for a list of supported data types.
An argument can also inherit its complexity (whether its value is a real or complex number) from the signal that is connected to it. To inherit complexity, set the Complexity field on the Data properties dialog to Inherited.
After you build the model, the Compiled Type column of the Ports and Data Manager gives the actual type inherited from Simulink in the compiled simulation application.
The inherited type of output data is inferred from diagram actions
that store values in the specified output. In the preceding example,
computed from operations with double operands, which yield results
double. If the expected type matches the
inferred type, inheritance is successful. In all other cases, a mismatch
occurs during build time.
Library MATLAB Function blocks can have inherited data types, sizes, and complexities like ordinary MATLAB Function blocks. However, all instances of the library block in a given model must have inputs with the same properties.
When you select Built-in for Data type mode, the Data properties dialog displays a Data type field that provides a drop-down list of supported data types. You can also choose a data type from the Data Type column in the Ports and Data Manager. The supported data types are:
64-bit double-precision floating point
32-bit single-precision floating point
32-bit signed integer
16-bit signed integer
8-bit signed integer
32-bit unsigned integer
16-bit unsigned integer
8-bit unsigned integer
Boolean (1 =
You can specify the types of MATLAB Function block function arguments as expressions in the Ports and Data Manager.
<data type expression> from
the Type drop-down menu of the Data properties
In the Type field,
<data type expression>”
with an expression that evaluates to a data type. The following expressions
MATLAB Function blocks can represent signals and parameter values as fixed-point numbers. To simulate models that use fixed-point data in MATLAB Function blocks, you must install the Fixed-Point Designer™ product on your system.
You can set the following fixed-point properties:
Signedness. Select whether you want the fixed-point
data to be
Signed data can represent positive and negative quantities. Unsigned
data represents positive values only. The default is
Word length. Specify the size (in bits) of the word that will hold the quantized integer. Large word sizes represent large quantities with greater precision than small word sizes. Word length can be any integer between 0 and 128 bits. The default is 16.
Scaling. Specify the method for scaling your fixed point data to avoid overflow conditions and minimize quantization errors. You can select the following scaling modes:
If you select this mode, the Data Type Assistant displays the Fraction Length field, specifying the binary point location.
Binary points can be positive or negative integers. A positive integer moves the binary point left of the rightmost bit by that amount. For example, an entry of 2 sets the binary point in front of the second bit from the right. A negative integer moves the binary point further right of the rightmost bit by that amount, as in this example:
The default is 0.
If you select this mode, the Data Type Assistant displays fields for entering the Slope and Bias.
You can enter slope and bias as expressions that contain parameters defined in the MATLAB workspace.
You should use binary-point scaling whenever possible to simplify the implementation of fixed-point data in generated code. Operations with fixed-point data using binary-point scaling are performed with simple bit shifts and eliminate the expensive code implementations required for separate slope and bias values.
Data type override. Specify whether the data type
override setting is
Inherit (default) or
Calculate Best-Precision Scaling. The Simulink software
can automatically calculate “best-precision” values
Binary point and
and bias scaling, based on the Limit range properties
To automatically calculate best precision scaling values:
Specify Minimum, Maximum, or both Limit range properties.
Click Calculate Best-Precision Scaling.
The Simulink software calculates the scaling values, then displays them in either the Fraction Length, or Slope and Bias fields.
The Limit range properties do not apply to
Therefore, Simulink cannot calculate best-precision scaling for
Fixed-point Details. You can view the following Fixed-point details:
|Representable maximum||The maximum number that can be represented by the chosen data type, sign, word length and fraction length (or data type, sign, slope and bias).|
|Maximum||The maximum value specified.|
|Minimum||The minimum value specified.|
|Representable minimum||The minimum number that can be represented by the chosen data type, sign, word length and fraction length (or data type, sign, slope and bias).|
|Precision||The precision for the given word length and fraction length (or slope and bias).|
If you set the Data Type Override mode to
Single in Simulink,
the MATLAB Function block sets the type of all inherited
input signals and parameters to
fi double or
single objects respectively (see MATLAB Function Block with Data Type Override (Fixed-Point Designer) for
more information). You must check the data types of your inherited
input signals and parameters and use the Ports and Data Manager (see Ports and Data Manager) to set explicit
types for any inputs that should not be fixed-point. Some operations,
sin, are not applicable to fixed-point
If you do not set the correct input types explicitly, you may encounter compilation problems after setting Data Type Override.