AL2100-DS00-R datasheet(16/52 Pages) BOARDCOM

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AL2100

Preliminary Data Sheet

11/11/02

Broa d c om Co rp o r a ti o n

Page 8

Fault Propagation

Document

AL2100-DS01-405-R

REDUNDANT LINK

The AL2100 supports redundant links through the use of the DATA_OFF and REDUN signals. The redundant link function

is only available for the fiber port. An implementation of a redundant link is shown in Figure 4. The redundant link can also

be configured with two fiber switch-ports, a far-end fault signaling support required, and two AL2100s.

There are two scenarios: either redundant link transmits a link fault or the receive link fault triggers the redundant link.

Figure 4: Redundant Link

RECEIVE LINK FAULT

In the event of a receive-link failure, the receiver goes into a link-down mode. The AL2100 takes the following actions:

•

Starts transmitting the remote fault signal

•

Puts the TXP and TXN pins in high-impedance mode

•

De-asserts the DATA_OFF signal

The far-end primary transceiver is normally in a link-up state, and a back-up transceiver is in a link-fail state. During receive-

link failure, the local AL2100 enables data transmission of the backup transceiver by asserting the REDUN signal. The

backup AL2100 starts sending copies of the transmit signal. The primary far-end receiver that receives the RF signal enters

the link-fail state. The back-up transceiver exits the link-fail state upon receiving a signal from the local AL2100, re-

establishing the link. When the primary link is repaired, the REDUN is de-asserted.

TRANSMITS LINK FAULT

The 100BASE-FX specification provides a way to detect a transmit-link failure. Whenever a fiber receiver experiences a

receive-link failure, it transmits a far-end fault signal. The far-end fault signal is indicated by the far-end fault IDLE signal (84

Local

Primary

AL2100

Primary

Data_off

Far End

Back up

AL2100

Far End

Primary

AL2100

Transformer

Redun#

Data_off

Local

Back up

AL2100

Redun#

Redundant Link

Back up

Redun

AL2100-DS00-R Datasheet(PDF) 16 Page - Broadcom Corporation.

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