Recommended Practices :: Generating HDL Code with the Embedded MATLAB Function Block (Simulink® HDL Coder™)

Recommended Practices

On this page…
Introduction Use Compiled External M-Functions on the Embedded MATLAB Path Build the Embedded MATLAB Code First Use the hdlfimath Utility for Optimized FIMATH Settings Use Optimal Fixed-Point Option Settings

On this page…

Introduction

Use Compiled External M-Functions on the Embedded MATLAB Path

Build the Embedded MATLAB Code First

Use the hdlfimath Utility for Optimized FIMATH Settings

Use Optimal Fixed-Point Option Settings

Introduction

This section describes recommended practices when using the Embedded MATLAB Function block for HDL code generation.

By setting Embedded MATLAB Function block options as described in this section, you can significantly increase the efficiency of generated HDL code. See Setting Optimal Fixed-Point Options for the Embedded MATLAB Function Block for an example.

Use Compiled External M-Functions on the Embedded MATLAB Path

The coder supports HDL code generation from Embedded MATLAB Function blocks that include compiled external M-functions. This feature lets you write reusable M-code and call it from multiple Embedded MATLAB Function blocks.

Such functions must be defined in M-files that are on the Embedded MATLAB path, and must include the %#eml compilation directive. See Adding the Compilation Directive %#eml in the Embedded MATLAB documentation for information on how to create, compile, and invoke external M-functions.

Build the Embedded MATLAB Code First

Before generating HDL code for a subsystem containing an Embedded MATLAB Function block, it is strongly recommended that you build the Embedded MATLAB code to check for errors. To build the code, select Build from the Tools menu in the Embedded MATLAB Function block editor (or press CTRL+B).

Use the hdlfimath Utility for Optimized FIMATH Settings

The M-function hdlfimath.m is a utility that defines a FIMATH specification that is optimized for HDL code generation. It is strongly recommended that you replace the default FIMATH for fixed-point signals specification with a call to the hdlfimath function, as shown in the following figure.

The following listing shows the FIMATH setting defined by hdlfimath.

hdlfm = fimath(...
    'RoundMode', 'floor',...
    'OverflowMode', 'wrap',...
    'ProductMode', 'FullPrecision', 'ProductWordLength', 32,...
    'SumMode', 'FullPrecision', 'SumWordLength', 32,...
    'CastBeforeSum', true);

Note When the FIMATH OverflowMode property of the FIMATH specification is set to 'Saturate', HDL code generation is disallowed for the following cases: