XRT75VL00D datasheet(36/92 Pages) EXAR

36 / 92 page

XRT75VL00D

E3/DS3/STS-1 LINE INTERFACE UNIT WITH SONET DESYNCHRONIZER

REV. 1.0.3

As defined in ITU-T G.775, an LOS condition is also declared between 10 and 255 UI (or E3 bit periods) after

the actual time the LOS condition has occurred. The LOS condition is cleared within 10 to 255 UI after

restoration of the incoming line signal. Figure 20 shows the LOS declaration and clearance conditions.

5.4.3

Muting the Recovered Data with LOS condition:

When the LOS condition is declared, the clock recovery circuit locks into the reference clock applied to the

ExClk pin and output this clock on the RxClk output. The data on the RPOS and RNEG pins can be forced to

zero by pulling the LOSMUT pin “High” (in Hardware Mode) or by setting the LOSMUT bits in the individual

channel control register to “1” (in Host Mode).

NOTE: When the LOS condition is cleared, the recovered data is output on RPOS and RNEG pins.

FIGURE 20. LOSS OF SIGNAL DEFINITION FOR E3 AS PER ITU-T G.775.

Actual Occurrence

of LOS Condition

Line Signal

is Restored

Time Range for

LOS Declaration

Time Range for

LOS Clearance

G.775

Compliance

G.775

Compliance

0 UI

10 UI

0 UI

10 UI

255 UI

RTIP/

RRing

RLOS Output Pin

XRT75VL00D Datasheet(PDF) 36 Page - Exar Corporation