In addition to receiving configuration request packets, the PCI Express Endpoint might receive TLP requests that are not processed within the PCI Express hard block. Typical TLP requests received are Vendor Defined
Messages and Read Requests. Before stage 2 is loaded, TLP requests return unsupported
requests (URs). After stage 2 has been loaded, the mcap_design_switch
output is asserted and TLP requests function as defined by the user design.