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Keysight N5990A-301 PCI Express Link Training Suite User Guide
5
Using the Software
The three control tabs are:
Equal - Sets the de-emphasis and pre-shoot in dB
Tap - Sets the FIR tap coefficients
Ampl - Sets the emphasized and de-emphasized voltage levels
Note that when any slider is moved, the corresponding parameter
will be written to the hardware immediately. Click the “
Apply”
or
“Apply Levels”
button.
Bit Error Rate Measurement
Click
Start BER Measurement
(
Figure 38
), to automatically poll the
J-BERT's bit and error counters. By default, the displayed BER (Bit
Error Rate) is calculated from the total number of bits and total
number of errors. Click the
Accum
button to the left side of the BER
display to toggle to the current BER, which is the calculated BER of
the last error counter reading. Note that these values may not
necessarily be always equal to the BER displayed in the J-BERT,
since the measurement intervals might be different.
Figure 38
Bit Error Rate Measurements
Click
Reset BER Measurement
to reset the bit and error counters.
The BER can be used to determine whether link training was
successful or not. A very high value of BER and increasing error
count could indicate that link training was not performed, because
the error counter is always programmed to only compare the
loop-back pattern.
