SCI without interruption of the algorithm

Hi, (sorry for my english) I'm developing a control strategy for a synchronous generator using the ADC and eQEP modules of the f28335 DSP in Simulink. The algorithm works fine if I don't include the SCI module, so I supose the problem is relationed with the priority task. How can I achieve lower priority to the SCI module?. I think this is very interesting for all we are working with DSP in Simulink.

Thanks, Francisco