Changing the duty ratio online in Embedded Target

I am programming a F28335 board (TI's experimenters kit) with the help of Embedded Coder building blocks in SIMULINK. I have generated a simple code to set a duty ratio for PWM generation. However i want to be able to change the duty ratio while the code is executing ont he board wihtout having to rebuild the code again and again. Please help how to get started on this. I know i am supposed to use the SCI but there is no document i could find how to set this up.