The RTL8304E-CG is a 4-port Fast Ethernet switch controller that integrates memory, four MACs, and two physical layer transceivers for 10Base-T and 100Base-TX operation into a single chip.
The RTL8304E supports two MII/RMII interface for external devices to connect to the 3rd and 4th MACs. The external device could be a routing engine, HomePNA, HomePlug, or another processor depending on the application.