HDL Coder™ supports both predefined and user-defined System objects for code generation.
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 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.
You can create user-defined System objects for HDL code generation. For an example, see Generate Code for User-Defined 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.
UseMatrixTypesInHDL attribute
must be set to ‘off’, if you have a System
object in
your MATLAB code.
Enumerations are not supported.
Global variables are not supported.
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.
Predefined System objects are not supported for HDL code generation from within a MATLAB System block.
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.
To learn how to use System objects for HDL code generation, view the MATLAB designs in the following examples: