Agilent Technologies N4906B Serial BERT User Manual page 160

Evaluating Results
160
NO TE
If the gaps between data bursts are greater than 1 second (or 100 ms
in the measurement log file), they may be visible in the accumulated
results graph.
• Burst Status
The following states may be returned:
– No Error
No burst errors have occurred (any of those listed below).
– Gate Signal Too Long
This error can occur if there are too many bits within a burst. The
limit is 4 Gbit. At 13 Gb/s, this occurs roughly after 0.3 s (slower
frequencies have a higher gate-in period). This error has a higher
priority than "no unique 48bits".
– No Unique 48 Bits Found
For reliable synchronization, a pattern must contain a unique 48-
bit pattern (the detect word). If the current pattern does not have
a detect word, this error occurs.
If this status occurs, the synchronization may be incorrect, as
could also the measured bit error rate. There are standard
patterns that may contain more than one instance of the used
detect word. Statistically, every other burst would be correctly
synchronized.
In this case, it is recommended that you redefine the pattern.
This error can only occur with memory-based patterns.
– Unknown
The status is unknown. This can occur if accumulation has not
been started, or if Burst Sync mode has not been activated.
• Burst Sync Ratio
Percentage of time in burst (while the Gate In signal is low) that
patterns are in sync and error counting is active. A higher
percentage is desirable, because it indicates that more data is
measured during each burst.
Burst Sync Ratio =
• Total Burst Count
Total number of bursts received while in burst mode during the
accumulation period.
Agilent N4906B Serial BERT, User's Guide, October 2005
Bit Count Time
CDR Settling Time + Synchronization Time + Bit Count Time
Accumulated Measurements