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Fixed-Point Support for MATLAB System Objects

For information on working with Fixed-Point features, refer to the Fixed-Point topic.

Getting Information About Fixed-Point System Objects

System objects that support fixed-point data processing have fixed-point properties, which you can display for a particular object by typing vision.<ObjectName>.helpFixedPoint at the command line.

See Displaying Fixed-Point Properties to set the display of System object fixed-point properties.

The following Computer Vision System Toolbox™ objects support fixed-point data processing.

 Fixed-Point Data Processing Support

Displaying Fixed-Point Properties

You can control whether the software displays fixed-point properties with either of the following commands:

  • matlab.system.showFixedPointProperties

  • matlab.system.hideFixedPointProperties

at the MATLAB® command line. These commands set the Show fixed-point properties display option. You can also set the display option directly via the MATLAB preferences dialog box. Select the Preferences icon from the MATLAB desktop, and then select System Objects. Finally, select or deselect Show fixed-point properties.

If an object supports fixed-point data processing, its fixed-point properties are active regardless of whether they are displayed or not.

Setting System Object Fixed-Point Properties

A number of properties affect the fixed-point data processing used by a System object. Objects perform fixed-point processing and use the current fixed-point property settings when they receive fixed-point input.

You change the values of fixed-point properties in the same way as you change any System object property value. You also use the Fixed-Point Designer™ numerictype object to specify the desired data type as fixed-point, the signedness, and the word- and fraction-lengths.

In the same way as for blocks, the data type properties of many System objects can set the appropriate word lengths and scalings automatically by using full precision. System objects assume that the target specified on the Configuration Parameters Hardware Implementation target is ASIC/FPGA.

If you have not set the property that activates a dependent property and you attempt to change that dependent property, a warning message displays. For example, for the vision.EdgeDetector object, before you set CustomProductDataType to numerictype(1,16,15) you must set ProductDataType to 'Custom'.

    Note:   System objects do not support fixed-point word lengths greater than 128 bits.

    For any System object™ provided in the Toolbox, the fimath settings for any fimath attached to a fi input or a fi property are ignored. Outputs from a System object never have an attached fimath.

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