AM79C985 datasheet(22/48 Pages) AMD

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Am79C985

PRELIMINARY

eIMR+/HIMIB Interconnection

The eIMR+ device interfaces directly to the HIMIB de-

vice for full repeater manageability. To this end, the

eIMR+ device has a management port and a serial out-

put that allows the HIMIB device to monitor port activity.

The eIMR+ device is designed to allow one or two

eIMR+ devices to operate with a single HIMIB device.

Because the HIMIB device can monitor nine ports (8 TP

ports & 1 AUI port), one of the eIMR+ AUI ports is not

managed (statistics not kept). When two eIMR+ devices

are connected to a HIMIB device, one is designated the

primary device and the other is designated the second-

ary device. This designation serves to identify which

device has the managed AUI port. The primary device

has the managed AUI port and TP4-7. The secondary

device has the unmanaged AUI port and TP0-3. Figure

6 shows how the HIMIB and eIMR+ devices are inter-

connected.

When only one eIMR+ device is connected to a HIMIB

device, the AUI port is managed. The HIMIB device

treats the twisted-pair ports as TP0-3.

Although the HIMIB device does not monitor the AUI

port on the secondary eIMR+ device, the AUI port on

the secondary device defaults to enabled at reset. The

port can be disabled via the Secondary AUI Port Enable

command.

Management Port Interface

The eIMR+ management port is made up of six signals:

SI, SI_D, SO, CRS, CRS_I, and SCLK. SI is the serial

input from an external management module or the

HIMIB device. On the secondary eIMR+ device, SI_D

is the response input from the primary eIMR+ device. It

is also used at reset to set the eIMR+ device as either

a primary or secondary device. CRS transmits the state

of the eIMR+ device’s internal carrier sense signals.

Figure 6. eIMR-to-HIMIB Connection

AUIU Port & TP[3:0]

CRS_I

SI_D

CRS

eIMR+

(Secondary)

SCLK SI

AUIM Port & TP[7:4]

CRS_I

SI_D

CRS

eIMR+

(Primary)

SCLK SI

SCLK

CRS

HIMIB

b) Two eIMR Devices Connected to a HIMIB

AUIM Port & TP[3:0]

CRS_I

SI_D

CRS

eIMR+

SCLK SI

SCLK

CRS

HIMIB

a) One eIMR Device Connected to a HIMIB

VDD

DVSS

20651B-11

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