Specify the direct feedthrough status of a block's ports
void ssSetInputPortDirectFeedThrough(SimStruct *S, int_T port, int_T dirFeed)
Use in mdlInitializeSizes or mdlSetWorkWidths (after ssSetNumInputPorts) to specify the direct feedthrough (0 or 1) for each input port index. If not specified, the default direct feedthrough is 0. Setting direct feedthrough to 0 for an input port is equivalent to saying that the corresponding input port signal is not used in mdlOutputs or mdlGetTimeOfNextVarHit. If it is used, you might or might not see a delay of one simulation step in the input signal. This might cause the simulation solver to issue an error due to simulation inconsistencies.