GS3471 datasheet(26/179 Pages) SEMTECH

26 / 179 page

GS3471

Final Data Sheet Rev.4

PDS-060498

September 2017

26 of 179

Semtech

www.semtech.com

The CLI readout value has a multiplication resolution of 1 between 0h and 7Fh. In the

range from 80h to EFh the measurement resolution of CLI is reduced, and CLI value

increments by a multiple of 3.

Note: Any additional loss due to other transmission line elements (such as patch panels,

barrels, extra connectors, etc.) also translates to an equivalent cable length based on the

cable scaling factor.

4.3.2 Programmable Squelch Threshold

The GS3471 features a programmable squelch threshold, set through the device's host

interface. It impacts Equalizer Loss of Signal (EQ LOS) status. As shown in Figure 4-4,

squelch only affects the EQ LOS status when the Equalizer bits, BYPASS, and SLEEP[1:0]

in EQ_CONF_REG_0 are all 0.

The device continually compares the strength of the input signal as set in the

CABLE_LENGTH_INDICATOR bits in the STATUS_REG_0 register to the squelch

threshold set by the SQUELCH_THRESHOLD bits in the EQ_CONF_REG_1 register.

When the value reported by the CABLE_LENGTH_INDICATOR bits exceeds the value

programmed by the SQUELCH_THRESHOLD bits by 3 or more, the Equalizer Loss of

Signal (EQ LOS) status bit in the STATUS_REG_0 register is set to 1.

When the value reported by the CABLE_LENGTH_INDICATOR bits falls below the value

programmed by the SQUELCH_THRESHOLD bits by 3 or more, the Equalizer Loss of

Signal (EQ LOS) status bit in the STATUS_REG_0 register is set to 0.

This ±2 hysteresis around the SQUELCH_THRESHOLD setting avoids chattering of the

EQ LOS bit status for input signal strengths right around the threshold setting.

By default, the squelch threshold is set to the maximum possible level, and therefore

squelch is disabled.

4.3.3 Equalizer Loss of Signal (EQ LOS)

The Equalizer Loss of Signal (EQ LOS) status indicates whether or not a signal that meets

the device‘s programmed thresholds is present at its input. When EQ LOS is de-asserted

(set to 0), a supported input signal has been detected. Figure 4-4 shows how EQ LOS is

derived.

The EQ LOS function continuously monitors conditions of the input signal. In EQ Sleep,



EQ Auto-Sleep, or EQ Bypass modes, this is limited to carrier detection.

Table 4-3: Cable Length Scaling Factors

Cable Type

CLI Scaling Factor

Belden 1694A

2.5

Belden 8281

1.77

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