XRT83SL34 datasheet(23/80 Pages) EXAR

23 / 80 page

XRT83SL34

QUAD T1/E1/J1 SH TRANSCEIVER WITH CLOCK RECOVERY AND JITTER ATTENUATOR

PRELIMINARY

REV. P1.0.8

RECEIVE MONITOR MODE

In applications where Monitor mode is desired, the equalizer can be configured in a gain mode which handles

input signals attenuated resistively up to 29dB, along with 0 to 6dB cable attenuation for both T1 and E1

applications, refer to Table 5 for details. This feature is available in both Hardware and Host modes.

RECEIVER LOSS OF SIGNAL (RLOS)

For compatibility with ITU G.775 requirements, the RLOS monitoring function is implemented using both

analog and digital detection schemes. If the analog RLOS condition occurs, a digital detector is activated to

count for 32 consecutive zeros in E1 (4096 bits in Extended Los mode, EXLOS = “1”) or 175 consecutive zeros

in T1 before RLOS is asserted. RLOS is cleared when the input signal rises +3dB (built in hysteresis) above

the point at which it was declared and meets 12.5% ones density of 4 ones in a 32 bit window, with no more

than 16 consecutive zeros for E1. In T1 mode, RLOS is cleared when the input signal rises +3dB (built in

hysteresis) above the point at which it was declared and contains 16 ones in a 128 bit window with no more

than 100 consecutive zeros in the data stream. When loss of signal occurs, RLOS register indication and

causing the interrupt pin (INT) to go low. Once the alarm status register has been read, it will automatically

reset upon read (RUR), and the INT pin will return high.

Analog RLOS

Setting the Receiver Inputs to -15dB T1/E1 Short Haul Mode

By setting the receiver inputs to -15dB T1/E1 short haul mode, the equalizer will detect the incoming amplitude

and make adjustments by adding gain up to a maximum of +15dB normalizing the T1/E1 input signal.

NOTE: This is the only setting that refers to cable loss (frequency), not flat loss (resistive).

Once the T1/E1 input signal has been normalized to 0dB by adding the maximum gain (+15dB), the receiver

will declare RLOS if the signal is attenuated by an additional -9dB. The total cable loss at RLOS declaration is

typically -24dB (-15dB + -9dB). A 3dB hysteresis was designed so that transients will not trigger the RLOS to

clear. Therefore, the RLOS will typically clear at a total cable attenuation of -21dB. See Figure 6 for a simplified

diagram.

Setting the Receiver Inputs to -29dB T1/E1 Gain Mode

By setting the receiver inputs to -29dB T1/E1 gain mode, the equalizer will detect the incoming amplitude and

make adjustments by adding gain up to a maximum of +29dB normalizing the T1/E1 input signal.

NOTE: This is the only setting that refers to flat loss (resistive). All other modes refer to cable loss (frequency).

Once the T1/E1 input signal has been normalized to 0dB by adding the maximum gain (+29dB), the receiver

will declare RLOS if the signal is attenuated by an additional -9dB. The total cable loss at RLOS declaration is

FIGURE 6. SIMPLIFIED DIAGRAM OF -15dB T1/E1 SHORT HAUL MODE AND RLOS CONDITION

Norm alized up to +15dB Max

Declare LOS

Clear LOS

-9dB

+3dB

Clear LOS

Declare LOS

+3dB

-9dB

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