Instrument Function
R&S
®
SMU200A
183Operating Manual 1007.9845.32 ─ 15
"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,
this may be caused by the following:
●
The selected PRBS is not correct. For the bit error rate measurement,
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 (see
"Clock Slope" parameter).
●
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
Signal Generator 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 standard 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 will
not be started at the right time. The signal on the "Restart" line ena-
bles the measurement to be started optimally at the beginning of the
sequence.
SCPI command:
:BERT:RESult on page 514
5.4.10.2 Configuration
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
Selects the type of measurement: single or continuous measurement.
Bit and Block Error Rate Measurements - BERT Block
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