PRELIMINARY

This document contains information on a product under development at Advanced Micro Devices. The

information is intended to help you evaluate this product. AMD reserves the right to change or discontinue

work on this proposed product without notice.

Publication# 17306

Rev: B Amendment/0

Issue Date: January 1999

1-71

Am79C981

Integrated Multiport Repeater Plus™ (IMR+™)

DISTINCTIVE CHARACTERISTICS

s Enhanced version of AMD’s Am79C980

Integrated Multiport Repeater™ (IMR™) chip

with the following enhancements:

— Additional management port features

— Minimum mode provides support for an extra

four LED outputs per port for additional status in

non-intelligent repeater designs

— Pin/socket-compatible with the Am79C980

IMR chip

— Fully backward-compatible with existing IMR

device designs

s Interfaces directly with the Am79C987 HIMIB™

device to build a fully managed multiport

repeater

s CMOS device features high integration and low

power with a single +5 V supply

s Repeater functions comply with IEEE 802.3

Repeater Unit specifications

s Eight integral 10BASE-T transceivers utilize the

required predistortion transmission technique

s Attachment unit interface (AUI) port allows

connectivity with 10BASE-5 (Ethernet) and

10BASE-2 (Cheapernet) networks, as well as

10BASE-F and/or Fiber Optic Inter-Repeater

Link (FOIRL) segments

s On-board PLL, Manchester encoder/decoder,

and FIFO

s Expandable to increase number of repeater

ports

s All ports can be separately isolated (partitioned)

in response to excessive collision conditions or

fault conditions

s Network management and optional features are

accessible through a dedicated serial

management port

s Twisted-pair Link Test capability conforming to

the 10BASE-T standard. The receive Link Test

function can be optionally disabled through the

management port to facilitate interoperability

with devices that do not implement the Link Test

function

s Programmable option of Automatic Polarity

Detection and Correction permits automatic

recovery due to wiring errors

s Full amplitude and timing regeneration for

retransmitted waveforms

s Preamble loss effects eliminated by deep FIFO

GENERAL DESCRIPTION

The Integrated Multiport Repeater Plus (IMR+) chip is a

VLSI circuit that provides a system-level solution to de-

signing a compliant 802.3 repeater incorporating

10BASE-T transceivers. The device integrates the

Repeater functions specified by Section 9 of the IEEE

802.3 standard and Twisted-Pair Transceiver functions

complying with the 10BASE-T standard. The Am79C981

provides eight integral twisted-pair medium attachment

units (MAUs) and an attachment unit interface (AUI) port

in an 84-pin plastic leaded chip carrier (PLCC).

A network based on the 10BASE-T standard uses un-

shielded twisted-pair cables, thereby providing an eco-

nomical solution to networking by allowing the use of

low-cost unshielded twisted-pair (UTP) cable or existing

telephone wiring.

The total number of ports per repeater unit can be in-

creased by connecting multiple IMR+ devices through

their expansion ports, minimizing the total cost per re-

peater port. Furthermore, a general-purpose attach-

ment unit interface (AUI) provides connection capability

to 10BASE-5 (Ethernet) and 10BASE-2 (Cheapernet)

coaxial networks, as well as 10BASE-F and/or Fiber

Optic Inter-Repeater Link (FOIRL) fiber segments. Net-

work management and test functions are provided

through TTL-compatible I/O pins.

The IMR+ device interfaces directly with AMD’s

Am79C987 Hardware Implemented Management In-

formation Base™ (HIMIB) chip to build a fully managed

multiport repeater as specified by the IEEE 802.3

(Layer Management for 10 Mb/s Baseband Repeaters)

standard. When the IMR+ and HIMIB devices are

interconnected, complete repeater and per-port statis-

tics are maintained and can be accessed on demand

using a simple 8-bit parallel interface.