VITESSE

SEMICONDUCTOR CORPORATION

Datasheet

VSC834

2.5Gb/s 17x17 Crosspoint Switch

with Input Signal Activity (ISA) Monitoring

Page 4

G52247-0, Rev 4.2

02/09/01

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If any change in a monitor state occurs after sampling by MONCLK, an interrupt will be signalled by

asserting INTB, and the user must identify the offending channel by reading the monitor states. The interrupt

will be cleared when the corresponding activity monitor is read, but the monitor state will not be changed. If

multiple monitors have triggered the interrupt, it will persist until all the corresponding monitors have been

read.

The LOA circuitry requires a minimum signal level of 30-150 mV peak-peak to recognize an input as

active. This is required to distinguish noise on an unconnected signal (where both inputs float to the termination

voltage) from activity on a live signal. A minimum of two transitions defines activity. The threshold signal

level can be adjusted with the VHYS pin, which can set the threshold from zero to the maximum allowed input

swing. The VHYS pin will self-bias to a nomial value that will be appropriate for most applications (30-150mV

p-p input level). Although uncalibrated for nominal level, gain and linearity, the VHYS pin can be externally

set to adjust the threshold level over the entire range of the input signal, from zero to the maximum level

allowed at the input.

Table 2: Memory Map

Address

Access

Description

00h

R/W

Output Y0’s programmed input channel ( write and then assert CONFIG to program)

01h

R/W

Output Y1’s programmed input channel

...

...

...

10h

R/W

Output Y16’s programmed input channel

11h

R/W

Internal output Y17’s programmed input channel

...

...

...

20h

R/W

Internal output Y32’s programmed input channel

21h

R/O

Rx Activity monitor for inputs A0, A1,A2,A3

( Logic ‘1’=No activity)

22h

R/O

Rx Activity monitor for inputs A4, A5,A6,A7

23h

R/O

Rx Activity monitor for inputs A8, A9,A10,A11

24h

R/O

Rx Activity monitor for inputs A12, A13,A14,A15

25h

R/O

Rx Activity monitor for input A16