The RTL8305/RTL8305S is a highly integrated layer 2 single chip switch controller which incorporates 5 MACs (Media Access Controller), 5 physical layer transceivers, 1-Mbit SRAM and 1K-entry look-up table into one single chip. The RTL8305/RTL8305S contains 5 ports, and each one provides support for a 10Base-T (10Mbps) or 100Base-TX (100Mbps) network connection. The fifth port (port 4) can be configured as a MII/SNI to work with a routing engine, HomePHY or a fiber transceiver for a 100Base-FX application. And each operation mode can be easily set up by hardware strapping upon restart or power-on. The RTL8305S is designed for a stand-alone switch system through hardware strapping upon reset to achieve unmanaged operation and can be easily integrated with xDSL/Cable modem router. With the least peripheral components and using a 25MHz crystal, the RTL8305S has the best system cost structure. The integrated RTL8305S chip benefits from low power consumption and ease of use for SOHO 5-port switch or xDSL/Cable router applications.