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Multirate Model Requirements for HDL Code Generation

Model Configuration Parameters

Before generating HDL code, configure the parameters of your model using the hdlsetup command. This sets up your multirate model for HDL code generation. This section summarizes settings applied to the model by hdlsetup that are relevant to multirate code generation. These include:

  • Solver options that are recommended or required for HDL code generation:

    • Type: Fixed-step.

    • Solver: Discrete (no continuous states). Other fixed-step solvers could be selected, but this option is usually best for simulating discrete systems.

    • Treat each discrete rate as a separate task: Clear for single tasking mode.

  • hdlsetup configures the following Diagnostics / Sample time options for all models:

    • Multitask data transfer: error

    • Single task data transfer: error

    In multirate models intended for HDL code generation, Rate Transition blocks must be explicitly inserted when blocks running at different rates are connected. Set Multitask data transfer and Single task data transfer to error to detect illegal rate transitions before code is generated.

To learn more about the settings that hdlsetup configures, see Check for model parameters suited for HDL code generation.

Sample Rate

HDL Coder™ requires that at least one valid sample rate (sample time > 0) must exist in the model. If all rates are 0, –1, or –2, the code generator (makehdl) and compatibility checker (checkhdl) terminates with an error message.

Blocks To Use For Rate Transitions

Use Rate Transition blocks, rather than the following blocks, to create rate transitions in models intended for HDL code generation:

  • Delay

  • Tapped Delay

  • Unit Delay

  • Unit Delay Enabled

  • Zero-Order Hold

The Delay blocks listed should be configured to have the same input and output sample rates.

Zero-Order Hold blocks must be configured with inherited (-1) sample times.