User`s guide

3 Getting Started with MEX-Files
3-10
Data Type
The input and output vectors for the Simulink S-function must be
double-precision vectors or scalars. You must ensure that the variables you use
in the M-code for input and output are also double-precision values.
Note Simulink S-functions that are generated via the -S option of the
Compiler are not currently compatible with Real-Time Workshop
®
.Theycan,
however, be used to rapidly prototype code in Simulink.