This is machine translation

Translated by Microsoft
Mouseover text to see original. Click the button below to return to the English version of the page.

Note: This page has been translated by MathWorks. Click here to see
To view all translated materials including this page, select Country from the country navigator on the bottom of this page.

Specify Fixed-Point Data Types

Simulink® allows you to create models that use fixed-point numbers to represent signals and parameter values. Use of fixed-point data can reduce the memory requirements and increase the speed of code generated from a model.

To execute a model that uses fixed-point numbers, you must have the Fixed-Point Designer™ product installed on your system. Specifically, you must have the product to:

  • Update a Simulink diagram (Ctrl+D) containing fixed-point data types

  • Run a model containing fixed-point data types

  • Generate code from a model containing fixed-point data types

  • Log the minimum and maximum values produced by a simulation

  • Automatically scale the output of a model using the autoscaling tool

If the Fixed-Point Designer product is not installed on your system, you can execute a fixed-point model as a floating-point model by enabling automatic conversion of fixed-point data to floating-point data during simulation. See Overriding Fixed-Point Specifications for details.

If you do not have the Fixed-Point Designer product installed and do not enable automatic conversion of fixed-point to floating-point data, an error occurs if you try to execute a fixed-point model.


You do not need the Fixed-Point Designer product to edit a model containing fixed-point blocks, or to use the Data Type Assistant to specify fixed-point data types, as described in Specifying a Fixed-Point Data Type.

Fixed-point data types that resolve to a base integer type do not require a Fixed-Point Designer license. For example, a block or signal that specifies a data type of fixdt(1,8,0), which is equivalent to the int8 built-in type will not check out a Fixed-Point Designer license.

Overriding Fixed-Point Specifications

Most of the functionality in the Fixed-Point Tool is for use with Fixed-Point Designer. However, even if you do not have Fixed-Point Designer, you can configure data type override settings to simulate a model that specifies fixed-point data types. In this mode, Simulink temporarily overrides fixed-point data types with floating-point data types when simulating the model.


If you use fi objects or embedded numeric data types in your model or workspace, you might introduce fixed-point data types into your model. You can set fipref to prevent the checkout of a Fixed-Point Designer license.

To simulate a model without using Fixed-Point Designer, enter the following at the command line.

set_param(gcs, 'DataTypeOverride', 'Double', ...
'DataTypeOverrideAppliesTo', 'AllNumericTypes')

If you use fi objects or embedded numeric data types in your model, set the fipref DataTypeOverride property to TrueDoubles or TrueSingles (to be consistent with the model-wide data type override setting) and the DataTypeOverrideAppliesTo property to All numeric types.

For example, at the MATLAB® command line, enter:

 p = fipref('DataTypeOverride', 'TrueDoubles', ...
		'DataTypeOverrideAppliesTo', 'AllNumericTypes');

See Also


Related Topics