Instrument Function
R&S
®
SMBV100A
191Operating Manual 1176.8016.02 ─ 17
"No Sync"
The measurement is not synchronized.
Generally, a measurement cannot be synchronized until a clock and
a data signal have been detected. If synchronization still does not
occur, it can be caused by:
●
The selected PRBS is not correct. For the bit error rate measure-
ment, the PRBS sequence on which the data is based must be
set on the bit error rate tester. If the PRBS is not correct, the BER
measurement cannot synchronize to the data (due to the incorrect
polynomial).
●
A wrong clock slope is used, which violates setup or hold times.
●
The travel times of clock and data are unfavorable (e.g. clock
slope at data change). Check the relationship of clock to data
using an oscilloscope and optimize the travel times (e.g. clock
slope when the data signal applied is stable).
●
Reflections on the clock line occur, clocking the data signal into
the BER measurement twice, e.g. on lines without termination.
The R&S SMBV input is not terminated.
●
Incorrect polarity of data signal (or "Data Enable" signal).
In this case, the PRBS cannot synchronize. Note that an inversion
of the output signal specified for some cases by the PRBS stan-
dard is performed automatically upon PRBS selection. Manual
inversion of the data signal is therefore not required.
No sync status and an error rate of approx. 50%:
●
A bit error occurs during synchronization (e.g. nine data bits with
PRBS9). The BER measurement is set up incorrectly. This fault is
internally detected and automatically corrected.
●
If data that is not cyclically continued (i.e. when a break in the
sequence occurs at the memory wrap-around), the measurement
does not start at the right time. The signal on the "Restart" line
enables the measurement to be started optimally at the beginning
of the sequence.
Remote command:
:BERT:RESult? on page 535
5.4.10.2 Configuration Settings
The "Configuration" section is used to select the type of measurement, the data source
and the termination criteria. If the data is not cyclically continued, the measurement
can be selectively interrupted and restarted. Certain data areas and frames that have
been marked as faulty can be excluded from the measurement.
Mode........................................................................................................................... 192
Max Data Bits..............................................................................................................192
Max Errors...................................................................................................................192
PRBS.......................................................................................................................... 193
Data Polarity................................................................................................................193
Clock Slope................................................................................................................. 193
External Restart.......................................................................................................... 193
Data Enable................................................................................................................ 194
Bit and Block Error Rate Measurements
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