Start Fixed-Point Tool




fxptdlg('modelname') starts the Fixed-Point Tool for the Simulink® model specified by modelname. You can also access this tool by the following methods:

  • From the Simulink Analysis menu, select Data Type Design > Fixed-Point Tool.

  • From a subsystem context (right-click) menu, select Fixed-Point Tool.

In conjunction with Fixed-Point Designer™ software, the Fixed-Point Tool provides convenient access to:

  • Model and subsystem parameters that control the signal logging, fixed-point instrumentation mode, and data type override. (see Model Parameters)

  • Plotting capabilities that enable you to plot data that resides in the MATLAB® workspace, namely, simulation results associated with Scope, To Workspace, and root-level Outport blocks, in addition to logged signal data (see Signal Logging)

  • An interactive automatic data typing feature that proposes fixed-point data types for appropriately configured objects in your model, and then allows you to selectively accept and apply the data type proposals

You can launch the Fixed-Point Tool for any system or subsystem, and the tool controls the object selected in its System under design pane. If Fixed-Point Designer software is installed, the Fixed-Point Tool displays the name, data type, design minimum and maximum values, minimum and maximum simulation values, and scaling of each model object that logs fixed-point data. Additionally, if a signal saturates or overflows, the tool displays the number of times saturation or overflow occurred.


The Fixed-Point Tool works only for models that simulate in Normal mode. The tool does not work when you simulate your model in Accelerator or Rapid Accelerator mode.

Overriding Fixed-Point Specifications

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

  1. Enter the following at the command line.

    set_param(gcs, 'DataTypeOverride', 'Double',...
  2. 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');

Introduced before R2006a

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