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# 20651

Rev: B Amendment/0

Issue Date: January 1998

Am79C985

enhanced Integrated Multiport Repeater Plus (eIMR+™)

DISTINCTIVE CHARACTERISTICS

s Repeater functions compliant with IEEE 802.3

Repeater Unit specifications

s Direct interface with the Am79C987 Hardware

Implemented Management Information Base

(HIMIB™) device for building a basic managed

multiport repeater

s Full software backwards compatibility with

existing hub designs using Integrated Multiport

Repeater Plus (IMR+™)/HIMIB devices

s Network management and optional feature

accessibility through a dedicated serial

management port

s Four integral 10BASE-T transceivers with on-

chip filtering eliminating the need for external

filter modules on the 10BASE-T transmit-data

(TXD) and receive-data (RXD) lines

s One Reversible Attachment Unit Interface

(RAUI™) port used either as a standard IEEE-

compliant AUI port for connection to a Medium

Attachment Unit (MAU) or a reversed port for

direct connection to a Media Access Controller

(MAC)

s Low cost suitable for managed multiport

repeater designs

s Number of repeater ports easily expandable

with support for up to seven eIMR+ devices

without the need for an external arbiter

s All ports capable of being individually isolated

(partitioned) in response to excessive collision

conditions or fault conditions

s Flexible LED support for individual port status

and network utilization LEDs

s Programmable extended distance mode on RXD

lines allowing connection to cables longer than

100 meters

s Link Test function and Link Test pulse

transmission capable of being disabled through

the management port allowing devices that do

not implement the Link Test function to work

with the eIMR+ device

s Programmable automatic polarity detection and

correction option permitting automatic

recovery from wiring errors

s Full amplitude and timing regeneration for

retransmitted waveforms

s CMOS device with a single +5-V supply

GENERAL DESCRIPTION

The enhanced Integrated Multiport Repeater Plus

(eIMR+) device is a VLSI integrated circuit that pro-

vides a system-level solution to designing managed

multiport repeaters. The device integrates the repeater

functions specified in Section 9 of the IEEE 802.3

standard and Twisted Pair Transceiver functions

com-

plying with the 10BASE-T standard.

The eIMR+ device provides four Twisted Pair (TP) ports

and one reversible AUI (RAUI) port for direct connec-

tion to a MAC. The total number of ports per repeater

unit can be increased by connecting multiple eIMR+

devices through their expansion ports, hence, minimiz-

ing the total cost per repeater port.

The eIMR+ device also provides a connection to the

Am79C987 HIMIB device. The HIMIB device monitors

all the necessary counters, attributes, actions, and

notifications specified by IEEE 802.3, Section 19

(Layer Management for 10 Megabit per second (Mbps)

Baseband Repeaters). When the eIMR+ and HIMIB

devices are used together as a chip set, they provide a

cost-effective solution to the problem of designing

10BASE-T basic managed multiport repeaters.

The device is fabricated in CMOS technology and

requires a single +5-V supply.