rs485 address simulink desktop real-time

I am trying to communicate using rs485 with 3 instruments using Simulink Desktop Real-Time. Due to space and cable restrictions, they are all sharing the same communication lines so the instruments each have their own unique address. I can easily communicate with all of them using these IDs in MatLab, but I'm struggling to understand how to implement this in Simulink Desktop Real-Time using the Packet Input/Output blocks.

Are there any suggestions or existing models that could provide a solution for this?

Thanks!