Teledyne LeCroy QPHY-DDR4 - Manual (Page 70)

Shown on this screen:
• Z2 is a zoom of F2, the acquired DQS signal after any probe deskew has been applied. The zoom is
positioned at the location of the “worst case” tWPST measurement indicated by t@tWPSTmin. A
trace label is applied on this trace according to the signal name assigned to DQS to indicate
where the interpolation algorithm has determined where the device is no longer driving and Vref.
Figure 64 – tWPRE/tWPST Results
In the Measure section:
• tWPST (P1) is measuring the time from DQS begins to return to idle to the last falling edge on DQS
at Vref. The low level quit time is indicated by the trace label which is found through interpolation.
Essentially the time between the two trace labels is measured. The minimum value is the
measured value for tWPST min reported in mtCK(avg). This test is considered informational only
since the limit is undefined.
• tDQDQS (P2) is measuring the skew between DQ and DQS. Since this measurement is performed
once per burst, this shows how many W bursts were in the acquired waveform.
• t@tWPSTmin (P4) displays the location of where the minimum value of tWPST occurred. This is
used to position the zoom traces at the location of the “worst case results”.
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