User guide

7
Press OK to confirm your settings.
Pattern Synchronization - Reference
The error detector can synchronize the data patterns in the following ways:
• In Normal Sync Mode, you can choose between
–
Automatic Sync
With this option selected, the error detector constantly tries to synchronize
the patterns when the BER threshold is exceeded.
–
Manual
Manual synchronization can be selected, for example, if the signal delay is
very unstable, and you want to avoid that the re-synchronization process
affects the measurement results.
•
Burst Sync Mode
Click this button to enable the Burst Sync Mode. Burst mode operates as
follows: For each burst of data, BER measurements are only made after the
error detector synchronizes to the incoming pattern. The signal at the Gate In
port controls the timing of synchronization and error counting for each burst.
N O T E
The burst sync mode is disabled in "8B/10B Comparison", "Bit Comparison without
PCIe3 SKPOS" and "Bit Comparison without USB3.1 SKPOS" error ratio modes.
The Sync Threshold defines when the error detector assumes the patterns to be
synchronized. The Serial BERT shifts the received pattern bitwise until the
measured BER is below this threshold.
Mask Resync Errors
The masking feature is available in all error ratio modes ("Bit Comparison", "8B/
10B Symbol Comparison", "Bit Comparison without PCIe3 SKPOS" and "Bit
Comparison without USB3.1 SKPOS" modes).
Some DUTs may drop bits respectively symbols due to high stress during receiver
test. For example; SATA drops complete symbols if the received symbol is illegal
(because of a bit error). Other cases of unexpected more data are added symbols
because of a bit error in a filler symbol so that the filler won’t be recognized
anymore. All cases of dropped or additional bits causes the error detector to lose
synchronization.
If the error detector loses synchronization it keeps counting bit, symbol, frame
errors and generally the measurement won’t reflect the DUT’s performance
5 Setting up the Error Detector
218 Agilent J-BERT N4903B High-Performance Serial BERT