Regarding AC Input test conditions and Slew rate definition in DDR2 Specification

When i am reading DDR2 specifications,i got 2 different definitions for input signal slew rate , one is fromJESD79-2F and another is from JESD8-15A.JESD79-2F says:       Falling skew  = (Vref- Vil(ac)max)/delta TFand  Rising skew   =(Vih(ac)min-Vref) / delta TRJESD8-15A(SSTL_18) says :        Falling skew  = (Vih(dc)min- Vil(ac)max)/delta TFand  Rising skew   = (Vih(ac)min-Vil(dc)max) / delta TR.Why this difference in definition, which one to be considered.

Specification DDR DDR2 Skew

malli.1729 7 years 1 month 19 days

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Answered byferhatyaldiz 7 years 1 month 19 days

Hi,For your all derating calculations and timing analysis you can considerfrom JESD79-2F for DDR2.Regards,Ferhat Yaldiz2013/12/9 mallikarjun K > When i am reading DDR2 specifications,> i got 2 different definitions for input signal slew rate , one is from> JESD79-2F and another is from JESD8-15A.>> JESD79-2F says:>        Falling skew  = (Vref- Vil(ac)max)/delta TF> and  Rising skew   =(Vih(ac)min-Vref) / delta TR>> JESD8-15A(SSTL_18) says :>         Falling skew  = (Vih(dc)min- Vil(ac)max)/delta TF> and  Rising skew   = (Vih(ac)min-Vil(dc)max) / delta TR.>> Why this difference in definition, which one to be considered.>>>>