XRT83SL314 datasheet(27/85 Pages) EXAR

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XRT83SL314

14-CHANNEL T1/E1/J1 SHORT-HAUL LINE INTERFACE UNIT

PRELIMINARY

REV. P1.0.5

In T1 mode, RLOS is declared if an incoming signal has no transitions over a period of 175 +/-75 contiguous

pulse intervals. However, the XRT83SL314 LIU has a built in analog RLOS so that the user can be notified

when the amplitude of the incoming signal has been attenuated -9dB below the equalizer gain setting. For

example:

In T1 or E1 short haul mode, the equalizer gain setting is 15dB.

Once the input reaches an

amplitude of -24dB below nominal, the LIU will declare RLOS. The RLOS circuitry clears when the input

reaches +3dB relative to where it was declared. This +3dB value is a pre-determined hysteresis so that

transients will not cause the RLOS to clear. In E1 mode, RLOS is declared if an incoming signal has no

transitions for N consecutive pulse intervals, where 10

≤N≤255. According to G.775, no transitions in E1 mode

is defined between -9dB and -35dB below nominal. Figure 14 is a simplified block diagram of the analog

RLOS function. Table 6 summarizes the analog RLOS values for the different equalizer gain settings.

FIGURE 14. ANALOG RECEIVE LOS OF SIGNAL FOR T1/E1/J1

NOTE: For programming the equalizer gain setting on a per channel basis, see the microprocessor register map for details.

2.6.3.2

EXLOS (Extended Loss of Signal)

By enabling the extended loss of signal by programming the appropriate channel register, the digital RLOS is

extended to count 4,096 consecutive zeros before declaring RLOS in T1 and E1 mode. By default, EXLOS is

disabled and RLOS operates in normal mode.

2.6.3.3

AIS (Alarm Indication Signal)

The XRT83SL314 adheres to the ITU-T G.775 specification for an all ones pattern. The alarm indication signal

is set to "1" if an all ones pattern (at least 99.9% ones density) is present for T, where T is 3ms to 75ms in T1

mode. AIS will clear when the ones density is not met within the same time period T. In E1 mode, the AIS is

set to "1" if the incoming signal has 2 or less zeros in a 512-bit window. AIS will clear when the incoming signal

has 3 or more zeros in the 512-bit window.

TABLE 6: ANALOG RLOS DECLARE/CLEAR (TYPICAL VALUES) FOR T1/E1

GAIN SETTING

DECLARE

CLEAR

15dB (Short Haul Mode)

-24dB

-21dB

29dB (Monitoring Gain Mode)

-38dB

-35dB

Normalized up to EQC[4:0] Setting

Declare LOS

Clear LOS

-9dB

+3dB

Clear LOS

Declare LOS

+3dB

-9dB

Normalized up to EQC[4:0] Setting

XRT83SL314 Datasheet(PDF) 27 Page - Exar Corporation

XRT83SL314 Datasheet(HTML) 27 Page - Exar Corporation

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