User guide

italics. A BER value for which a Contour does not exist is struck across. You can
select multiple BER values. The lower BER values are in red and pink, while the
deep BER values are in green and blue. The screen shot below displays the contour
and the legend.
The outer contour represents the measured BER contour, while the inner lines are
extrapolated. For more details on extrapolation see“Estimated Total Jitter” on page
245
The Minimum Number of Errors indicates the minimum number of hits required to
plot the contour.
Eye Mask Measurement
Masks are marked regions on the screen. When the mask region and waveform
intersect it is called a violation. The Mask test shows the quality of the eye.
When the mask measurement begins, the instrument either aligns the mask as per
the eye levels of the waveform, or as per the absolute voltages specified in the
mask file. The position of the mask can be changed by scaling the mask according
to the eye. Once the masks are positioned the mask test counts the number of
times a particular pixel falling in the mask region has been measured. The mask
violations are marked in green. A consolidated report of the test is available on the
left bottom of the graph. The user can turn off the mask computation by pressing
the “stop” button.
6 Advanced Analysis
318 Agilent J-BERT N4903B High-Performance Serial BERT