User guide

•
Accumulation Period
For single and repeat accumulation modes, the accumulation period is
displayed here. The period will be displayed in elapsed seconds, error count, or
bit count, depending on the selected method.
Burst Results
The recommended application for burst mode is to measure multiple data bursts
in quick succession. In this way, you can accumulate data for all bursts together.
You may wish to accumulate the number of bits necessary for a statistically valid
BER measurement. Refer to “Introduction to Burst Sync Mode” on page 211 and
“Test Times and Confidence Levels” on page 27 for details.
When the accumulation period lasts for the duration of all bursts, the gaps in error
counting (while the Gate In signal was high) will not be included in BER
calculations. The gaps in error counting will not be considered error-free periods.
N O T E
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
Evaluating Results 7
Agilent J-BERT N4903B High-Performance Serial BERT 383