FINAL
Publication# 14395 Rev: DAmendment/0
Issue Date: May 1994
1

Am79C98

Twisted-Pair Ethernet Transceiver (TPEX)

DISTINCTIVE CHARACTERISTICS

n

CMOS device provides compliant operation and
low operating current from a single +5 V supply

n

Power Down mode provides reduced power
consumption for battery-powered applications.
Reset capability allows use in remote MAU
applications.

n

Pin-selectable twisted-pair receive polarity
detection and automatic inversion of the receive
signal. Polarity indication output pin can
directly drive an LED.

n

Pin-selectable twisted-pair Link Integrity Test
capability conforming to the IEEE 802.3
standard for 10BASE-T. Link status pin can
directly drive an LED.

n

Internal twisted-pair transmitter digital
predistortion circuit reduces medium-induced
jitter and ensures compliance with the
10BASE-T transmit and receive waveform
requirements

n

Pin-selectable SQE Test (heartbeat) enable

n

Transmit and receive status indications are
available on separate, dedicated pins

n

AUI loopback, Jabber Control, and SQE Test
functions comply with the 10BASE-T standard
IEEE Std 802.3i-1990

GENERAL DESCRIPTION

The Am79C98 Twisted-Pair Ethernet Transceiver
(TPEX) is an integrated circuit that implements the
medium attachment unit (MAU) functions for the
twisted-pair medium, as specified by the IEEE 802.3
standard (Type 10BASE-T). This device provides the
necessary electrical and functional interface between
the IEEE 802.3 standard attachment unit interface
(AUI) and the twisted-pair cable.
A network based on the 10BASE-T standard can use
unshielded twisted-pair cables, providing an economi-
cal solution to networking by allowing the use of exist-
ing telephone wiring. The Am79C98 provides a minimal
component count and cost-effective solution to the
design and implementation of 10BASE-T standard
networks.
TPEX provides twisted-pair driver and receiver circuits,
including on-board transmit digital predistortion, re-
ceiver squelch, and an AUI port with pin-selectable
SQE Test enable. The device also provides a number of
additional features, including pin-selectable Twisted-
Pair Receive Polarity Detection and Automatic Polarity
Reversal, Link Status indication, Link Test disable func-
tion, and transmit and receive status. The Twisted-Pair
Polarity and Link Status pins can be used to drive LEDs
directly.
The Am79C98 is fabricated in CMOS technology and
requires a single +5 V supply. The device is available in
24-pin SKINNYDIP

®

plastic dual in-line and 28-pin
plastic leaded chip carrier (PLCC) packaging.