A system and apparatus combining a hub and a function as a single chip compound device. A single serial interface engine (SIE) is shared between a hub endpoint and a function endpoint. The hub endpoint and function endpoint being integrated on a single chip. A single backend interface is coupled between the SIE and the endpoints. The backend interface selects which of the hub endpoints or the function endpoints can access the shared SIE at any time period. In one embodiment, a first address is associated with the hub and a second address is associated with the function. The backend interface selects between the hub and function by comparing a translated address received from the SIE with each of the first address and the second address. The result of the comparisons via suitable combinational logic serves as a select signal for a multiplexer between the hub/function and the SIE.