The Host Interface ports on the FrontPanel Subsystem IP Core require special handling. The following ports collectively make up the Host Interface:
led_out port on the LEDs IP core also requires special handling.
Both the FrontPanel Subsystem and LEDs IP Cores constrain these ports to external pins. The IP Core needs to propagate these constraints, through the hierarchy, to top level ports. This connection cannot be obstructed by any intermediate logic from the point of instantiation through to the connection with the top level ports. It is not a requirement that the instantiation is placed in the top level module. The IP Core will trace the ports, through the hierarchy, to the top level ports, irrespective of the net/port names used at any point in the hierarchy or the port names used at the top level.