User`s guide

Examples of C MEX-File S-Function Blocks
3-93
* Normalize if this transfer function has direct feedthrough.
*/
num = ssGetRWork(S) + bankToUpdate*2*nCoeffs;
den = num + nCoeffs;
for (i = 1; i < nCoeffs; i++) {
num[i] -= den[i]*num[0];
}
/*
* Indicate oldest bank has been updated.
*/
ssGetIWork(S)[1] = 1;
}
} /* end mdlUpdate */
#define MDL_DERIVATIVES
/* Function: mdlDerivatives ===================================================
* Abstract:
* The derivatives for this block are computed by using a controllable
* state-space representation of the transfer function.
*/
static void mdlDerivatives(SimStruct *S)
{
int_T i;
int_T nContStates = ssGetNumContStates(S);
real_T *x = ssGetContStates(S);
real_T *dx = ssGetdX(S);
int_T nCoeffs = nContStates + 1;
int_T activeBank = ssGetIWork(S)[0];
const real_T *num = ssGetRWork(S) + activeBank*(2*nCoeffs);
const real_T *den = num + nCoeffs;
InputRealPtrsType uPtrs = ssGetInputPortRealSignalPtrs(S,0);
/*
* The continuous system is evaluated using a controllable state-space
* representation of the transfer function. This implies that the
* next continuous states are computed using:
*
* dx = Ax(t) + Bu(t)
* = [-a1 -a2 ... -an] [x1(t)] + [u(t)]
* [ 1 0 ... 0] [x2(t)] + [0]
* [ 0 1 ... 0] [x3(t)] + [0]
* [ . . ... .] . + .
* [ . . ... .] . + .
* [ . . ... .] . + .
* [ 0 0 ... 1 0] [xn(t)] + [0]
*
* where a1, a2, ... are the coefficients of the numerator polynomial:
*
* A(s) = s^n + a1 s^n-1 + a2 s^n-2 + ... + an-1 s + an