Agilent Technologies J-BERT N4903B, User Manual, Page: 200 / 572

Sync Now
Click this button to manually start a pattern synchronization. See “What Type of
Synchronization Should You Use?” on page 208 for information on when you
should use this function.
Note that this button is not available in bit recovery mode.
0/1 THReshold Center
Starts an auto-search function that sets the 0/1 threshold to the optimum point of
the incoming data eye on the vertical voltage axis without changing the data input
delay. This function can be used for determining the optimum 0/1 threshold for
asymmetric data eyes, or for patterns with an unequal mark density.
The status message bar will indicate if this function is unsuccessful. This function
clears the
Avg. 0/1 Threshold
checkbox.
N O T E
This function uses the alignment BER Threshold to determine the top and bottom
eye edges.
Data Center
This button starts an auto-search function that aligns the data signal with the clock
signal so that the error detector samples at the optimum point of the data eye in
the time axis. This automatically compensates for delays in the clock/data paths,
preventing unnecessary errors. The 0/1 decision threshold is not changed. The
status message bar will indicate if this function is unsuccessful.
N O T E
Ensure that the received clock frequency is stable before using Data Center.
T I P
The clock/data alignment process time is pattern dependent, and with some large
user patterns the alignment can take several minutes. If you encounter such a long
time with a user pattern, it may be possible to first perform clock/data alignment
on a pure PRBS pattern. This generally does not affect alignment accuracy, and can
minimize measurement time.
This tip does not apply in cases of severe pattern dependent jitter or with devices
that do not work with PRBS patterns.
N O T E
This function uses the alignment BER threshold to determine the left and right eye
edges.
5
Setting up the Error Detector
200 Agilent J-BERT N4903B High-Performance Serial BERT