Level 1 S-Function normalise state variable

As part of a 6DoF aircraft simulation that I am writing, I am using a Level 1 S-Function (was given it as a framework, may upgrade to Lvl 2 if necessary). As part of this simulation I need to normalise a quaternion. The code to normalise the quat is really easy, I just don't know how to modify the continuous state variables directly.

Thanks in advance, Ryan.

[Kaustubha Govind]

You can type "sfcndemo_limintm" at the MATLAB prompt to open a model that contains an S-function with a continuous state. Typically, the continuous state is updated in the flag==1 case. Look for the mdlDerivatives function.