User`s guide

3 Writing S-Functions As C-MEX files
3-78
#define MDL_SET_WORK_WIDTHS
#if defined(MDL_SET_WORK_WIDTHS) && defined(MATLAB_MEX_FILE)
/* Function: mdlSetWorkWidths ===================================================
* The width of the modes and the zero crossings depends on the width of the
* output. This width is not always known in mdlInitializeSizes so it is handled
* here.
*/
static void mdlSetWorkWidths(SimStruct *S)
{
int nModes;
int nNonsampledZCs;
if (ssIsVariableStepSolver(S) &&
ssGetSampleTime(S,0) == CONTINUOUS_SAMPLE_TIME &&
ssGetOffsetTime(S,0) == 0.0) {
int numOutput = ssGetOutputPortWidth(S, 0);
/*
* modes and zero crossings
* o One mode element will be needed for each scalar output
* in order to specify which equation is valid (1), (2), or (3).
* o Two ZC elements will be needed for each scalar output
* in order to help the solver find the exact instants
* at which either of the two possible "equation switches"
* One will be for the switch from eq. (1) to (2);
* the other will be for eq. (2) to (3) and vise-versa.
*/
nModes = numOutput;
nNonsampledZCs = 2 * numOutput;
} else {
nModes = 0;
nNonsampledZCs = 0;
}
ssSetNumModes(S,nModes);
ssSetNumNonsampledZCs(S,nNonsampledZCs);
}
#endif /* MDL_SET_WORK_WIDTHS */
/* Function: mdlOutputs =======================================================
* Abstract:
*
* A saturation is described by three equations.
*
* (1) y = UpperLimit
* (2) y = u
* (3) y = LowerLimit
*
* When this block is used with a fixed-step solver or it has a noncontinuous
* sample time, the equations are used as is.
*
* Now consider the case of this block being used with a variable step solver