# why pre-post amble is required?

why do we need pre-post amble for READ or WRITE DQS ?

1 ) one reason could be --> Because transitions of voltages from logic level 0 to 1 or 1 to 0 take time to complete: so the strobe is asserted a suitable time after the start of data lines transitions to tell the reader that the data is valid in the sense that the transitions between logic levels on the lines have been completed.

---------- but there is DQS to do this job....then why extra pre and post amble ?

• Delaying the incoming strobe for READs is more involved and will be covered in detail in an independent technical note. <-- Do you have idea on which exact independent technical note it is referring to ? I suppose for READ preamble, DQS is aligned with DQ , so why need to delay the incoming DQS strobe ? – kevin998x Feb 21 at 14:31