AM79C984 datasheet(27/44 Pages) AMD

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P R E L I M I N A R Y

Am79C984A

Link Test Status of TP ports

SI Data

1101 0000

SO Data

0000 L3..L0

n = 0

TP Port n in Link Test Failed

n = 1

TP port n in Link Test Passed

where

n is a port number in the range 0–3.

The response to this command gives the Link Test sta-

tus of all the TP ports. A disabled port continues to report

Link Test status. Re-enabling the port causes the port

to be placed in the Link Test Fail state.

Receive Polarity Status of TP Ports

SI Data

1110 0000

SO Data

0000 P3......P0

n = 0

TP Port n Polarity Correct

n = 1

TP port n Polarity Reversed

where

n is a port number in the range 0–3.

The response to this command gives the Received Po-

larity status of all the TP ports. If the polarity is detected

as reversed for a TP port, then the eIMR device will set

the appropriate bit in this command’s result only if the

Polarity Reversal Function is enabled for that port.

MJLP Status

SI Data

1111 0000

SO Data

M000 0000

Each eIMR device contains an independent MAU Jab-

ber Lock Up Protection timer. The timer is designed to

inhibit the transmit function of the eIMR device if it has

been transmitting continuously for more than 65536 bit

times. This bit remains set and is only cleared when the

MJLP status is read using this command.

Version

SI Data

1111 1111

SO Data

0000 0011

The response to this command gives the version of the

eIMR device. 0011 was chosen to help distinguish the

eIMR device from the IMR (Am79C980) and the IMR+

(Am79C981) devices.

SYSTEMS APPLICATIONS

eIMR to TP Port Connection

The eIMR device provides a system solution to designing

non-managed multiport repeaters.The eIMR device con-

nects directly to AC coupling modules for a 10BASE-T

hub. Figure 7 shows the simpliﬁed connection.

Twisted Pair Transmitters

TXD signals need to be properly terminated to meet the

electrical requirement for 10BASE-T transmitters. Prop-

er termination is shown in Figure 8 which consists of a

110-

Ω resistor and a 1:1 transformer.The load is a twisted-

pair cable that meets IEEE 802.3, Section 14.4 speciﬁ-

cations. The cable is terminated at the opposite end by

100

Ω.

Twisted Pair Receivers

RXD signals need to be properly terminated to meet the

electrical requirements for 10BASE-T receivers. Proper

termination is shown in Figure 9. Note that the receivers

do not require external ﬁlter modules.

AM79C984 Datasheet(PDF) 27 Page - Advanced Micro Devices

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