Abstract: An Ethernet circuit that combines the basic functionality of a twisted pair transceiver and a twisted pair/AUI encoder/decoder provides an autoswitching circuit that switches between a twisted pair data pathway and an AUI data pathway by changing from the twisted pair data pathway to the AUI data pathway when a link circuit fails to detect signals on the twisted pair medium and when the Ethernet circuit is not transmitting or executing a jabber procedure, and by changing from the AUI data pathway to the twisted pair data pathway when the link circuit detects signals on the twisted pair medium and when the Ethernet circuit is not transmitting or receiving.

Abstract: An Ethernet circuit which provides encoder, decoder, twisted pair transceiver, and AUI interface functions in accordance with the IEEE 802.3 standard. In addition, the Ethernet circuit provides a full duplex function for independent transmit and receive paths, a test function which allows testing of the circuit without disturbing the twisted pair medium and regardless of activity on the medium, and an isolation function which allows the Ethernet circuit to be connected to a serial network interface controller in parallel with other devices. The Ethernet circuit can include a twisted pair driver that includes a filter function, a shielded/unshielded cable driver function, and a low idle current driver function.