P R E L I M I N A R Y

18

Am79C984A

Notes:

1. CRS = Carrier Sense, COL = Collision, JAB = Jabber, LINK = Link, LB = Loop Back, PAR = Partition, DIS = Port Disabled,

blk = Blink (Number = period of Blink).

3. All LEDs blink 16 times at 260 ms per blink after reset.

4. All LEDs are on for approximately 4 seconds after reset.

LED software override is executed in two stages, by

first issuing the blink rate (Software Override of LED

Blink Rate) and then issuing the command to enable

the particular port LEDs (Enable Software Override of

Bank

A/B LEDs). All port combinations selected for

software override control will reference the blink rate

last issued by the Software Override of the LED Blink

Rate command.

put drivers that sink 12 mA of current to turn on the

LEDs. In a multiple eIMR configuration, the outputs

from the global LED drivers (LDGA and LDGB) of each

chip can be tied together to drive a single pair of global

status LEDs.

CRS and COL are extended to make it easier for visual

recognition; that is, they will remain active for some

time even if the corresponding condition has expired.

Once carrier sense is active, CRS will remain active for

a minimum of 4 ms. Once a collision is detected, COL

is active for at least 4 ms. The exception to this rule is

stretched to 100

µs.

true when DO on the MAU is successfully looped back

to DI on the AUI port. LB is false (off) if a loopback error

is detected, or if the AUI port is disabled or in the re-

verse mode. Transmit carrier sense is sampled at the

end of packet to determine the state of LB. The state of

LB remains latched until carrier sense is sampled again

for the next packet. The default/power-up state for LB is

false (off).

Figure 1 shows the recommended connection of LEDs.

LED lights.

Figure 1. Visual Monitoring Application—Direct

LED Drive

Network Activity Display

The eIMR status port can drive up to eight LEDs to in-

dicate the network-utilization level as a percentage of

bandwidth. The status port uses eight dedicated out-

LEDs in the series that will be lit increases as the

12 mA of current to turn on the LEDs. See Figure 2.

Table 2. LED Attribute-Monitoring Program Options

LED Control

Global LEDs

TP LEDs

AUI LEDs

LDGA

LDGB

0

0

0

CRS

COL

LINK (Note 2)

PAR

LB

PAR

0

0

1

CRS

COL

LINK

CRS

LB

CRS

0

1

0

Reserved (Note 5)

0

1

1

Reserved (Note 5)

1

0

0

CRS 260-ms blk

COL 260-ms blk

LINK

CRS 260-ms blk

PAR

COL 260-ms blk

CRS 260-ms blk

PAR

COL 260-ms blk

1

0

1

COL

JAB

LINK (Note 3)

CRS 512-ms blk

PAR (Note 3)

(Note 3)

CRS 512-ms blk

PAR (Note 3)

1

1

0

CRS

COL

LINK

CRS 130-ms blk

PAR or DIS

CRS 130-ms blk

PAR or DIS

1

1

1

CRS

COL

LINK (Note 4)

PAR 1.56-s blk

COL (Note 4)

(Note 4)

PAR 1.56-s blk

PAR (Note 4)

eIMR

LED

Interface

LDA[4:0]

LDB[4:0]

LDGA

LDGB

R

Typical

20650A-6

20650B-6