GS6151 datasheet(46/77 Pages) SEMTECH

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GS6151

Final Data Sheet

Rev.4

PDS-060389

August 2015

46 of 77

Semtech

Proprietary & Confidential

www.semtech.com

It is important to note that while the on-chip VCO is trimmed to within 0.5% of SMPTE

data rates, VT variation may extend the deviation from exact SMPTE data rates. If

frequency precision is required it is recommended to use the external pins or retimed

clock to provide a clock reference for the PRBS generator. The selection of reference

clock for the PRBS generator is done through programming the bits as in Table 4-11.

To enable the PRBS generator the PRBSGEN_ENABLE bit of the PRBS_GEN_CTRL register

must be set high. The PRBS bit stream starts on the falling edge of the PRBSGEN_START

bit. To output the PRBS generator on the trace driver output the OUTPUT_PRBS_DATA0

and/or OUTPUT_PRBS_DATA1 bits of the DRIVER_CONTROL_REG_0 register need to be

set to 1.

The PRBS generator can also output a clock instead of a PRBS7 bit stream. The clock

output is selected by setting the PRBSGEN_DATASEL bit of the PRBS_GEN_CTRL register

to 0. Both the PRBS7 generator and clock output can have their frequency of operation

divided by 1, 2, 4 or 8 by setting the PRBSGEN_DIV bits of the PRBS_GEN_CTRL register,

down to an output data rate of 125Mb/s.

Additionally, when either the On-Chip PRBSGEN VCO or the re-timed clock is used as the

clock reference for the PRBS generator the phase of the output can be coarsely adjusted

to 0, 90, 180 or 270º by programming PRBSGEN_PHASE bit of the PRBS_GEN_CTRL

Note: It is recommended that the AUTO_LOS_MUTE_ENABLE and

AUTO_PWRDN_DISABLE parameters are set to disabled when the PRBS generator uses

the on-chip PRBSGEN VCO or the external clock pins to avoid muting the (PRBS

generator) output upon loss of signal on the input pins.

Table 4-11: Reference Clock for the PRBS Generator

PRBS_EXT_CLK

PRBSGEN_CLKSEL

Clock Reference

On-chip PRBSGEN VCO

CDR re-timed clock

Clock reference pins (GS6151 only)

GS6151 Datasheet(PDF) 46 Page - Semtech Corporation