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Detect Fixed-Point Constant Precision Loss

This example shows how to detect fixed-point constant precision loss.

To open the model, at the MATLAB® command line, enter:

cd(fullfile(docroot,'toolbox','fixpoint','examples'))
ex_fixed_point_constant_precision_loss

For the Data Type Conversion block in this model:

  • Input slope, SU = 1

  • Output slope, SY = 1.000001

  • Net slope, SU/SY = 1/1.000001

To set up the model and run the simulation:

  1. For the Inport block, set the Data type to int16.

  2. For the Data Type Conversion block, set the Output data type to fixdt(1,16,1.000001,0).

  3. In the Configuration Parameters dialog box, set the Diagnostics > Type Conversion > Detect precision loss configuration parameter to error.

  4. In your Simulink® model window, in the Simulation tab, click Run.

When you simulate the model, a net slope quantization error occurs.

The Fixed-Point Designer™ software generates an error informing you that net scaling quantization caused precision loss. The message provides the following information:

  • The block that introduced the error.

  • The original value of the net slope.

  • The quantized value of the net slope.

  • The error in the value of the net slope.

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