Writing S-Functions

The SimStruct

The file matlabroot/simulink/include/simstruc.h is a C language header file that defines the Simulink data structure and the SimStruct access macros. It encapsulates all the data relating to the model or S-function, including block parameters and outputs.

There is one SimStruct data structure allocated for the Simulink model. Each S-function in the model has its own SimStruct associated with it. The organization of these SimStructs is much like a directory tree. The SimStruct associated with the model is the root SimStruct. The SimStructs associated with the S-functions are the child SimStructs.

Note    By convention, port indices begin at 0 and finish at the total number of ports minus 1.

Simulink provides a set of macros that S-functions can use to access the fields of the SimStruct. See SimStruct Functions, for more information.

S-Function Source File Requirements

Compiling C S-Functions