AM79C985KCW AMD [Advanced Micro Devices], AM79C985KCW Datasheet - Page 23

• Manufacturer Part Number: AM79C985KCW
• Manufacturer: AMD [Advanced Micro Devices]

When two eIMR+ devices are connected to one HIMIB
device, the secondary device transmits the status of its
TP ports, then transmits the status of the primary eIMR+
TP ports and AUI port (CRS and CI). Note that the sec-
ondary device does not transmit the status of its AUI
port. At Reset, the secondary device (and single eIMR+
device) internally synchronizes the CRS stream to begin
with the AUI CI bit. SO is the eIMR+ device response to
a Get command.
The pins SI_D and CRS_I are multi-purpose pins. Their
primary purpose is management input to the primary
eIMR+ device. They are also used to set the manage-
ment mode of the eIMR+ device. The mode is set on the
rising edge of RST. The settings are shown in Table 4.
Following reset, the eIMR+ devices retain their manage-
ment designations. However, CRS_I and SI_D return to
their management port functions.
Command/Response Timing
Figure 7 shows the command/response timing. At the
end of a GET command, the eIMR+ device waits two
SCLK cycles and then transmits the response on SO.
The secondary eIMR+ device stores the data received
on the SI_D input (from the primary eIMR+ device) in
an internal register. When it has transmitted D3 data, it
CRS_I
0
0
1
1
SCLK
Note: For SO on the Primary device, D[3:0] corresponds to TP[7:4].
SI_D
SO
SO
SI
0
1
0
1
Table 4. eIMR+ Device Management Designations
Figure 7. Management Get Command/Response
Primary eIMR+ Device or
Single eIMR+ Device
Secondary eIMR+ Device
ST D0 D1 D2 D3 D4 D5 D6 D7
Single eIMR+ Device
P R E L I M I N A R Y
Am79C985
ST D0 D1 D2 D3
ST D0 D1 D2 D3 D4 D5 D6 D7
appends the received response to the end of the SO
signal.
Following reset, after the eIMR+ devices have been as-
signed their primary and secondary designation, SO
and SI_D return to their management-port functions.
Port Activity
In addition to providing a means for receiving com-
mands and sending data in response to those com-
mands, the management port includes a CRS signal
that transmits the state of the eIMR+ device’s internal
carrier-sense signals.
When two eIMR+ devices are connected to one
Am79C987 HIMIB device (as shown in the System
Applications section), CRS_I of the secondary device
receives the following signals from the primary device:
the carrier-sense signals of the AUI port, the CI-bit sta-
tus of the AUI port, and the carrier-sense signals of the
TP ports. The secondary device transmits the status of
the AUI port (CRS and CI) for the primary device, the
status of its own TP ports (TP0-TP3), and then the sta-
tus of the primary device’s TP ports (TP4-TP7). The
status of the AUI port of the secondary device is not
retransmitted (see Figure 8).
Primary eIMR+ Device
Two eIMR+ Devices
Secondary eIMR+ Device
20651B-12
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