Teledyne LeCroy QPHY-DDR2 - Manual (Page 44)

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QPHY-DDR2-OM-E Rev A
tWPRE, Write Preamble
Time from when DQS begins to be driven (at the beginning of the preamble) to when it crosses Vref. This is only
measured on a write cycle.
tWPST, Write Postamble
Time from when DQS crosses Vref (at the beginning of the postamble) to when DQS stops being driven (at the
end of the postamble). This is only measured on a write cycle.
Prerequisite: SLEW of DQ and DQS, a derating factor is applied to the limit depending on the signals slewrate.
This is applicable for the following four tests.
tDS(base), DQ and DM Input Setup Time
Input waveform timing tDS with differential data strobe enabled, is referenced from the input signal crossing at the
VIH(ac)min level to the differential data strobe crosspoint at VREF for a rising signal, and from the input signal
crossing at the VIL(ac)max level to the differential data strobe crosspoint at VREF for a falling signal applied to the
device under test. See Figure 28 and Figure 29 as follows.
DQS and DQS# signals must be monotonic between VIL(dc)max and VIH(dc)min.
Setup (tDS) nominal slew rate for a rising signal is defined as the slew rate between the last crossing of VREF(dc)
and the first crossing of VIH(ac)min. Setup (tDS) nominal slew rate for a falling signal is defined as the slew rate
between the last crossing of VREF(dc) and the first crossing of VIL(ac)max.
JESD79-2E Specific Note 8 (page 85 to 94) with tables 43 and 44 explain the limit compensation versus the
slewrate of the measured signals. Timing limits are initially specified for input slewrate of 1V/ns for single-ended
signals and 2V/ns for differential signal (for DQS and CK).
tDH(base), DQ and DM Input Hold Time
Input waveform timing tDH with differential data strobe enabled, is referenced from the differential data strobe
crosspoint at VREF to the input signal crossing at the VIH(dc)min level for a falling signal and from the differential
data strobe crosspoint at VREF to the input signal crossing at the VIL(dc)max level for a rising signal applied to
the device under test. See Figure 28 and Figure 29 as follows.
DQS and DQS# signals must be monotonic between VIL(dc)max and VIH(dc)min.
Hold (tDH) nominal slew rate for a rising signal is defined as the slew rate between the last crossing of
VIL(dc)max and the first crossing of VREF(dc). Hold (tDH) nominal slew rate for a falling signal is defined as the
slew rate between the last crossing of VIH(dc)min and the first crossing of VREF(dc).