Maintaining Level-1 M-File S-Functions :: Writing S-Functions in M (Writing S-Functions)

Writing S-Functions

Maintaining Level-1 M-File S-Functions

Note The information provided in this section is intended only for use in maintaining existing M-file S-functions based on Level-1 API. You should use the more capable Level-2 API to develop new M-file S-functions (see Writing Level-2 M-File S-Functions).

A Level-1 M-file S-function consists of a MATLAB function of the following form

[sys,x0,str,ts]=f(t,x,u,flag,p1,p2,...)

where f is the name of the S-function. During simulation of a model, Simulink repeatedly invokes f, using the flag argument to indicate the task (or tasks) to be performed for a particular invocation. Each time the S-function performs the task and returns the results in an output vector.

A template implementation of an M-file S-function, sfuntmpl.m, resides in matlabroot/toolbox/simulink/blocks. The template consists of a top-level function and a set of skeleton subfunctions, called S-function callback methods, each of which corresponds to a particular value of flag. The top-level function invokes the subfunction indicated by flag. The subfunctions perform the actual tasks required of the S-function during simulation.

Runtime Object S-Function Arguments