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HDL Code Generation for System Objects

HDL Coder™ supports both predefined and user-defined System objects for code generation.

Why Use System Objects?

System objects provide a design advantage because:

  • You can save time during design and testing by using existing System object™ components.

  • You can design and qualify custom System objects for reuse in multiple designs.

  • You can define your algorithm in a System object once, and reuse multiple instances of it in a single MATLAB design.

    This idiom cannot be used with MATLAB functions that have state. For example, if the algorithm has state and requires the use of persistent variables, that function cannot be instantiated multiple times in a design. Instead, you would need to copy and rename the function for each instance.

  • HDL code that you generate from System objects is modular and more readable.

Predefined System Objects

Predefined System objects that are available with MATLAB®, DSP System Toolbox™, and Communications Toolbox™ are supported for HDL code generation. For a list, see Predefined System Objects Supported for HDL Code Generation.

User-Defined System Objects

You can create user-defined System objects for HDL code generation. For an example, see Generate Code for User-Defined System Objects.

Limitations of HDL Code Generation for System Objects

The following limitations apply to HDL code generation for all System objects:

  • Your design can call the step method only once per System object.

  • step must not be inside a nested conditional statement, such as a nested loop, if statement, or switch statement.

  • step must not be inside a conditional statement that contains a matrix indexing operation.

  • A System object must be declared persistent if it has state.

    A System object has state when it has a tunable private or public property, or a property with the DiscreteState attribute.

  • You can use the dsp.Delay System object only in feed-forward delay modeling.

  • Enumerations are not supported.

  • Global variables are not supported.

Supported Methods

For predefined System Objects, step is the only method supported for HDL code generation.

For user-defined System Objects, either the step method, or the output and update methods, are supported for HDL code generation.

Additional Restrictions for Predefined System Objects

Predefined System objects are not supported for HDL code generation from within a MATLAB System block.

Additional Restrictions for User-Defined System Objects

In addition to the limitations for all System objects, the following restrictions apply to user-defined System objects for HDL code generation:

  • In the setupImpl and resetImpl methods, if you assign values to properties or variables, the values must be constants.

  • If your design uses the output and update methods, it can call each method only once per System object.

  • Initial and reset values for properties must be compile-time constant.

  • User-defined System objects must not be public properties.

  • A step method with multiple outputs cannot be called within a conditional statement.

System object Examples for HDL Code Generation

To learn how to use System objects for HDL code generation, view the MATLAB designs in the following examples: