GS12341 datasheet(39/109 Pages) SEMTECH

39 / 109 page

GS12341

Final Data Sheet

Rev.1

PDS-061928

August 2019

39 of 109

Semtech

Proprietary & Confidential

www.semtech.com

4.7.2 Output Driver Polarity Inversion

While in data mode, the signal polarity may be inverted at the outputs through the

CTRL_OUTPUT<n>_ DATA_ INVERT parameters in register 0x48. This may be useful to

compensate for an inverted upstream signal or to facilitate board signal routing. To

invert the polarity of either of the two output drivers, write 1b to control parameter

CTRL_OUTPUT<n>_DATA_ INVERT.

4.7.3 Output Driver Data Rate Selection

By default, the GS12341 uses the SD trace driver output group settings for all data rates,

regardless of Reclocker lock condition or data rate being applied. The following

parameters are used to control the output for all data rates in the default condition:

 CFG_OUTPUT<n>_TD_SD_DRIVER_SWING

 CFG_OUTPUT<n>_TD_SD_PREEMPH_WIDTH

 CFG_OUTPUT<n>_TD_SD_PREEMPH_AMPL

 CFG_OUTPUT<n>_TD_SD_PREEMPH_PWRDWN

If required, per-rate selection of the trace driver output group setting is possible by

setting CTRL_OUTPUT<n>_TRDR_PER_RATE = 1. Once set, the trace driver output

group will be determined by the rate to which the Reclocker is locked. For example, if

the Reclocker is locked to 12G, the following parameters will be used to control the

output drivers.

 CFG_OUTPUT<n>_TD_12G_DRIVER_SWING

 CFG_OUTPUT<n>_TD_12G_PREEMPH_WIDTH

 CFG_OUTPUT<n>_TD_12G_PREEMPH_AMPL

 CFG_OUTPUT<n>_TD_12G_PREEMPH_PWRDWN

Note: If per-rate settings are being used, when the Reclocker is not locked the trace

driver will use the 12G trace driver output group settings.

4.7.4 Amplitude and Pre-Emphasis Control

The two output drivers offer very granular amplitude and pre-emphasis control. For

optimal loss compensation, both the pre-emphasis pulse amplitude and the

pre-emphasis pulse width can be independently configured on both output drivers.

This extra flexibility provides a mechanism to better shape the pre-emphasis gain to

match the frequency loss response of interconnect composed of trace, connector and

via losses. The swing and pre-emphasis can be independently configured for specific

data rates.

CFG_OUTPUT<n>_TD_SD_DRIVER_SWING (SD)

CFG_OUTPUT<n>_TD_HD_DRIVER_SWING (HD)

CFG_OUTPUT<n>_TD_3G_DRIVER_SWING (3G)

CFG_OUTPUT<n>_TD_6G_DRIVER_SWING (6G)

CFG_OUTPUT<n>_TD_12G_DRIVER_SWING (12G)

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