PRELIMINARY
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
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Full software backwards compatibility with
existing hub designs using Integrated Multiport
Repeater Plus (IMR+™)/HIMIB devices
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Network management and optional feature
accessibility through a dedicated serial
management port
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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
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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)
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Low cost suitable for managed multiport
repeater designs
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Number of repeater ports easily expandable
with support for up to seven eIMR+ devices
without the need for an external arbiter
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All ports capable of being individually isolated
(partitioned) in response to excessive collision
conditions or fault conditions
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Flexible LED support for individual port status
and network utilization LEDs
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Programmable extended distance mode on RXD
lines allowing connection to cables longer than
100 meters
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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
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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.
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
AMD [ ADVANCED MICRO DEVICES ]
