Teledyne LeCroy QPHY-USB3-Tx-Rx - Manual (Page 35)

QPHY-USB3-Tx-Rx Software Option
917719 Rev A
35
At the completion of this part of the Differential Voltage & De-emphasis Test the oscilloscope is in the following
configuration:
Figure 27 - Oscilloscope Configuration after Differential Voltage & De-emphasi s Test on CP7
On the screen are 2 visible traces. The first is the result of the ac quisition of the CP 7 signal after (optional) cable
de-embedded has been performed. The second is the histogram created from this signal. P1 and P2 are the 2
modes of the histogram. These 2 parameters only differ in the measurement gates that have been set . P3 is the
difference of the 2 modes.
Then this is repeated on the CP8 pattern. This pattern consists of the same 50- 250 1’s followed by 50-250 0’s
without de-emphasis applied to the signal. The histogram is creat ed and the difference between the 2 modes is
calculated. This result is the differential voltage (without de-emphasis). The differential voltage and the amplitude
of the de-emphasized bits are then used to calculate the de-emphasis ratio.