Some MATLAB toolboxes can write microcontroller codes for specific DSP chips only. For example some target TI and ANALOG DSP chips. But you can't tailor you embedded application in MATLAB the way C is being used in embedding the code. The purpose of connecting MATLAB to target chips is for the developers to minimize hard coding of teh DSP routines. You can check teh MATLAB help file or MATWORKS.com which chips are supported