Hi,
Only a few MCUs are supported natively in multisim. The model you are looking for is not on our database, you can try to find a SPICE model of the microcontroller around the web, though I doubt it, as they are really difficult to program. If you already know what to expect and are just looking for PCB design, I would suggest making a footprint of the model to use in a circuit.
Best of luck,
Miguel V
National Instruments
