The LXT971A is an IEEE compliant Fast Ethernet PHY Transceiver that directly supports both 100BASE-TX and 10BASE-T applications. It provides a Media Independent Interface (MII) for easy attachment to 10/100 Media Access Controllers (MACs). The LXT971A also provides a Low Voltage PECL (LVPECL) interface for use with 100BASE-FX fiber networks. This document also supports the LXT971 device. The LXT971A supports full-duplex operation at 10 Mbps and 100 Mbps. Its operating condition can be set using auto-negotiation, parallel detection, or manual control. The LXT971A is fabricated with an advanced CMOS process and requires only a single 3.3V power supply.