The DM9331A is a physical-layer, single-chip, low power transceiver for media converter application. On the media side, it provides a direct interface either to Unshielded Twisted Pair Category 5 Cable 5 (UTP5) for 100BASE-TX Fast Ethernet, and it also provides PECL interface to connect the external fiber optical transceiver. Through the Media Converter Interface (MCI), the DM9331A connects to another DM9331A for the twisted pair to the fiber media converter, or fiber to fiber repeater. The DM9331A uses a low-power and high-performance CMOS process. It contains the entire physical layer functions of 100BASE-TX as defined by IEEE802.3u, including the Physical Coding Sublayer (PCS), Physical Medium Attachment (PMA), Twisted Pair Physical Medium Dependent Sublayer (TP-PMD) and a PECL compliant interface for a fiber optical module, compliant with ANSI X3.166. The DM9331A provides a strong support for the auto-negotiation function, utilizing automatic selection of full or half-duplex mode. Furthermore, due to the built-in wave-shaping filter, the DM9331A needs no external filter to transport signals to the media on the 100base-TX Ethernet operation.