GS3281 datasheet(28/97 Pages) SEMTECH

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GS3281

Final Data Sheet

Rev.7

PDS-061453

January 2019

28 of 97

Semtech

Proprietary & Confidential

www.semtech.com

The vertical and horizontal scan information is useful when adjusting pre-emphasis and

equalization of a link. However, once this is accomplished, it may be sufficient to use the

eye scanner to only monitor jitter by setting the offsets to simply slice the eye at the

centre offset position, thus obtaining a simple 128 sample horizontal scan. A horizontal

eye can be configured to run in just over a millisecond.

In addition to the spatial parameters, the sample time, and thus the bit error rate

resolution for the eye scan can be adjusted; longer scans can detect finer bit error rates.

However, this proportionally increases the total scan time. The sample time in

microseconds is determined by a 32-bit time-out value split across two 16 bit registers.

See Table 4-6 for the register addresses and parameter names of the time-out eye scan

parameters.

For example, using the default spatial and temporal measurement scan parameters, the

scan time is approximately 6.6 seconds (32768 x 2 x100μs). However, by changing the

vertical and horizontal step size to 4, the scan time can be reduced to 400ms

(2048x2x100μs).

The error count information can be used as is to determine the minimum inner contour

based on the measurement time. However, the basic data can be post processed to

determine things like error rate, and error threshold.

The following equations provide guidance for user post-processing:

Equation 4-1

Contour maps can be created by defining error rate thresholds, and grouping sampled

points that fall between thresholds.

For example:

Equation 4-2

Some sampling scopes provide eye maps with BER contours; similar limited BER contour

approximations can be obtained from the eye scan by using BER threshold groups.

For example:

Equation 4-3

error

1rate

sample

1error1count

sample

1time

--------------------------------------------------------------

sample

1time

error

1rate1threshold11

------------------------------------------------------------------------ sample1error1threshold

sample

1time

error

1rate1threshold12

------------------------------------------------------------------------



sample

1time1x1data1rate

error

1rate1threshold11

------------------------------------------------------------------------------- sample1error1threshold sample1time1x1data1rate

error

1rate1threshold12

-------------------------------------------------------------------------------



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