VITESSE

SEMICONDUCTOR CORPORATION

Data Sheet

VSC7140

1.0625 Gb/s Fibre Channel

Dual Repeater / Hub Node

Page 4

G52180-0, Rev 4.0

10/23/00

©

VITESSE SEMICONDUCTOR CORPORATION • 741 Calle Plano • Camarillo, CA 93012

Tel: (800) VITESSE • FAX: (805) 987-5896 • Email: prodinfo@vitesse.com

Internet: www.vitesse.com

Dual Hub Mode

In this example, the VSC7140 is used to fully implement two adjacent nodes in a Fibre Channel Hub.

Incoming external signals on RX require retiming to improve amplitude and eliminate jitter before being used

by the Hub. The TX outputs drive the external device. A serial loop is formed by daisy chaining the SI to SO

paths of each node. The SDUs are required to configure the Hub to include external devices on the SI/SO loop

if they produce valid Fibre Channel data or to exclude them from the loop if they are not operational.

HUB is HIGH to select Hub Mode.

RX1 connects to the external output from Device #1. TX1 connects to the external input to Device #1.

RX2 connects to the external output from Device #2. TX2 connects to the external input to Device #2.

SI1 is connected to the SO2 output of the previous VSC7140. SI2 is pulled up SI2+ with 22k Ohms.

SO2 is connected to the SI1 input of the next VSC7140. SO1 is left unconnected.

If ERRSEL is HIGH, FAIL1- connects to SEL1 and FAIL2- connects to SEL2.

If ERRSEL is LOW, FAIL1- and FAIL2- are used by off-chip circuits to control SEL1 and SEL2.

Figure 2: Block Diagram: Use of VSC7140 in Hub Mode

Note: SO1 and SI2 not used.

VSC7140

Internal Loop

CRU

SDU

CRU

SDU

CRU

SDU

CRU

SDU

RX1

SI1

FAIL1

SEL1

FAIL2

SEL2

TX1

RX2

TX2

SO2