Implementing S-Functions - MATLAB & Simulink (original) (raw)
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MATLAB S-Functions
Level-2 MATLAB® S-functions allow you to create blocks with many of the features and capabilities of Simulink® built-in blocks, including:
- Multiple input and output ports
- The ability to accept vector or matrix signals
- Support for various signal attributes including data type, complexity, and signal frames
- Ability to operate at multiple sample rates
A Level-2 MATLAB S-function consists of a setup routine to configure the basic properties of the S-function, and a number of callback methods that the Simulink engine invokes at appropriate times during the simulation.
A basic annotated version of the template resides at [msfuntmpl_basic.m](https://mdsite.deno.dev/matlab:edit%28[matlabroot,'/toolbox/simulink/blocks/msfuntmpl%5Fbasic.m']%29;).
The template consists of a top-level setup function and a set of skeleton local functions, each of which corresponds to a particular callback method. Each callback method performs a specific S-function task at a particular point in the simulation. The engine invokes the local functions using function handles defined in the setup routine. See Level-2 MATLAB S-Function Callback Methods for a table of the supported Level-2 MATLAB S-function callback methods.
A more detailed Level-2 MATLAB S-function template resides at [msfuntmpl.m](https://mdsite.deno.dev/matlab:edit%28[matlabroot,'/toolbox/simulink/blocks/msfuntmpl.m']%29).
We recommend that you follow the structure and naming conventions of the templates when creating Level-2 MATLAB S-functions. This makes it easier for others to understand and maintain the MATLAB S-functions that you create. See Write Level-2 MATLAB S-Functions for information on creating Level-2 MATLAB S-functions.
MEX S-Functions
Like a Level-2 MATLAB S-function, a MEX S-function consists of a set of callback methods that the Simulink engine invokes to perform various block-related tasks during a simulation. MEX S-functions can be implemented in C, C++, or Fortran. The engine directly invokes MEX S-function routines instead of using function handles as with MATLAB S-functions. Because the engine invokes the functions directly, MEX S-functions must follow standard naming conventions specified by the S-function API.
An annotated C MEX S-function template resides at [sfuntmpl_doc.c](https://mdsite.deno.dev/matlab:edit%28[matlabroot,'/toolbox/simulink/blocks/src/sfuntmpl%5Fdoc.c']%29).
The template contains skeleton implementations of all the required and optional callback methods that a C MEX S-function can implement.
For a more basic version of the template see [sfuntmpl_basic.c](https://mdsite.deno.dev/matlab:edit%28[matlabroot,'/toolbox/simulink/blocks/src/sfuntmpl%5Fbasic.c']%29).
MEX Versus MATLAB S-Functions
Level-2 MATLAB and MEX S-functions each have advantages. The advantage of Level-2 MATLAB S-functions is speed of development. Developing Level-2 MATLAB S-functions avoids the time consuming compile-link-execute cycle required when developing in a compiled language. Level-2 MATLAB S-functions also have easier access to MATLAB toolbox functions and can utilize the MATLAB Editor/Debugger.
MEX S-functions are more appropriate for integrating legacy code into a Simulink model. For more complicated systems, MEX S-functions may simulate faster than MATLAB S-functions because the Level-2 MATLAB S-function calls the MATLAB execution engine for every callback method.
See Available S-Function Implementations for information on choosing the type of S-function best suited for your application.
See Also
Level-2 MATLAB S-Function | S-Function Builder | S-Function | MATLAB Function | Comparison of Custom Block Functionality