Am79C989

The Am79C989 Quad Ethernet Switching Transceiver (QuEST™) is a four-port physical layer (PHY) device that provides all of the analog functions needed for a 10BASE-T switch, including four independent Manchester Encode/Decode units (MENDECs) and four independent 10BASE-T transceivers. If the AUI port is used for a 10BASE-2, 10BASE-5, or 10BASE-FL transceiver, one of the four 10BASE-T ports is disabled.

The QuEST device is designed for 10 Mbps Ethernet switching hubs, port switching repeater hubs, routers, bridges, and servers that require data encoding and clock recovery on a per port basis and are limited by pin constraints.  lock recovery is performed as part of the MENDEC function. The QuEST device supports every physical layer function of a full-featured switch, including full-duplex operation with Auto-Negotiation and the ability to use various media types.

A unique feature of the QuEST device is the Quad AMD Switching Interface (QuASI) which multiplexes the data for all four channels into one set of pins. This minimizes the pin count and size of the QuEST device and substantially educes overall system cost.

The QuEST device provides a 2-pin Media Independent Interface (MII) Management Interface which supports the protocols specified in the IEEE 802.3u standard. Controlled by the switch system, this interface allows the QuEST device to be polled for status information and allows operating parameters of the QuEST device, such as extended distance operation, to be altered.

The Am79C989 device provides an Interrupt pin to indicate changes in the internal status of the device. The interrupt function reduces CPU polling of status registers and allows fast response time to changes in physical layer conditions.