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Model Referencing for HDL Code Generation

Benefits of Model Referencing for Code Generation

Model referencing in your DUT subsystem enables you to:

  • Partition a large design into a hierarchy of smaller designs for reuse, modular development, and accelerated simulation.

  • Incrementally generate and test code.

    HDL Coder™ incrementally generates code for referenced models according to the Configuration Parameters dialog box > Model Referencing pane > Rebuild options.

    However, HDL Coder treats If any changes detected and If any changes in known dependencies detected as the same. For example, if you set Rebuild to either If any changes detected or If any changes in known dependencies detected, HDL Coder regenerates code for referenced models only when the referenced models have changed.

How To Generate Code for a Referenced Model

By default, Generate VHDL code for model references into a single library is enabled. The VHDL code is generated in a single library instead of separate libraries. In this case, set the ScalarizePorts property to off before generating HDL code.

When generating code, if you encounter typing or naming conflicts between vector ports when interfacing two or more generated VHDL® code modules, use the ScalarizePorts property to generate non-conflicting port definitions. For more information, see Scalarize ports.

You can generate HDL code for the referenced model using the UI or the command line.

Using the UI

  1. Right-click the Model block and select HDL Code > HDL Block Properties.

  2. For Architecture, select ModelReference.

  3. Generate HDL code from your DUT subsystem.

Using the Command Line

  1. Set the Architecture property of the Model block to ModelReference. For example, for a DUT subsystem, mydut, that includes a model reference, referenced_model, enter this command:

    hdlset_param ('mydut/referenced_model', ... 
                  'Architecture', 'ModelReference');

  2. Generate HDL code for your DUT subsystem.

    makehdl ('mydut');

Generate Code for Model Arguments

To generate a single Verilog® module or VHDL entity for instances of a referenced model with different model argument values, see Generate Parameterized Code for Referenced Models.

Generate Comments

If you enter text in the Model Block Properties dialog box Description field, HDL Coder generates a comment in the HDL code.


  • Model block must have default values for the Block parameters.

  • Model block cannot be a masked subsystem.

  • Multiple model references that refer to the same model must have the same HDL block properties.

  • Referenced models cannot be protected models.

  • Hierarchical distributed pipelining must be disabled.

HDL Coder cannot move registers across a model reference. Therefore, referenced models can inhibit these optimizations:

  • Distributed pipelining

  • Constrained output pipelining

  • Streaming

When you have model references and generate HDL code, the generated model, validation model, and cosimulation model can fail to compile or simulate. To fix compilation or simulation errors, make sure that the referenced models are loaded or are on the search path.

The coder can apply the resource sharing optimization to share referenced model instances. However, you can apply this optimization only when all model references that point to the same referenced model have the same rate after optimizations and rate propagation. The model reference final rate may differ from the original rate, but all model references that point to the same referenced model must have the same final rate.