Teledyne LeCroy QPHY-DDR4 - Manual (Page 57)

QPHY-DDR4 Software Option
In the Measure section:
• tQH (P1) is measuring the hold time of DQ. The hold time is determined by measuring the time from
DQS at Vref to the next DQ transition at Vref . Essentially the time between the two trace labels is
measured. The minimum value is the measured value for tQH_total Min reported in mUI. 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 R bursts were in the acquired waveform.
• t@tQHmin (P4) displays the location of where the minimum value of tQH occurred. This is used to
position the zoom traces at the location of the “worst case results”.
tDQSCK, CK to DQS Skew
The purpose of this test is to characterize the allowed range for a rising data strobe edge relative to CK
on R bursts. This measures the time from
CK rising at Vref to the nearest DQS rising at Vref. Both the maximum
and minimum values are measured. This test is very similar to tDQSS, which is measured on W bursts.
After the completion of the tDQSCK test the oscilloscope is in the following configuration:
Figure 47 - Oscilloscope Configuration after the tDQSCK test
Shown on this screen:
• Z1 is a zoom of F1, the acquired CK signal after any probe deskew has been applied. The zoom is
position at the location of the “worst case” tDQSCK measurement indicated by t@tDQSCKmax. A
trace label is applied on this trace at Vref.
• 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” tDQSCK measurement indicated by
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