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questions about ddr3

Question asked by xilinx.moshi on Oct 28, 2014
Latest reply on Oct 31, 2014 by agxinmj

I've found that the maximum skew between DQ signals and their corresponding DQS must be less than 5ps for ddr3-1066(I'm simulating a board with xilinx FPGA and this is what it's needed for virtex-6). now I have three questions:

1- what is the definition of the skew between DQ and DQS?

2- how can I achieve this? I mean simulating the board in hyperlynx, and setting the probe to the die, is only the first step. then I simulate every single DQ net in a bytelane and the corresponding DQS. Is it correct to simulate single DQ and then load them altogether to view their skew?

3- if it's correct, how can I achieve +/- 5ps? I mean the rise and fall time of each individual DQ is not the same, so de-skewing the waveforms in their rising edges will result another skew in the falling edge which is greater than +/-5 ps.

 

really appreciate any answer.

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