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DRAM_ADRS_CNTRL Group length match

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  • DRAM_ADRS_CNTRL Group length match

    Hello Robert,

    In lesson-4, while reffering the net length match for ADRS-CNTRL group, i found a correction in spread sheet. please refer the snap shot for more details.

    Query,

    In spread sheet " IMX-6 Rex Module DDR3 Length Calculator-Spread sheet.xls" length for signal "DRAM_SDCLE0" is not entered for layer 2 which is 17Mil. Could you please tell why it is mentioned 0.
    During your vedio i found it as 17 and no negative values. (Pic-4)
    Could you please the reference document shared for lesson 4

  • #2
    From just looking at these pictures it looks like there should be 17. I am not sure why there is 0 - maybe a mistake? A very good spot meet

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    • #3
      Thank you Robert,
      one more concern is, if i enter the length as 17 mil to correct it, than final difference with clock signal comes as negative(-). Total length becomes more than clock length. Is it fine for design or clock length should not be exceeded.
      Could you please brief?
      Last edited by meet; 12-06-2017, 09:35 PM.

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      • #4
        I compared the spreadsheet from pic 4 with spreadsheet in pic 3 and the DRAM_SDCKE0 values in the purple and brown column are different. The best is to open the layout which you are checking and measure all the segments of DRAM_SDCKE0 signal. Double check if the lengths are the same as inserted in the spreadsheet. That should help.

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        • #5
          Hello Robert,
          Thank you for reply. i have one more query.

          1. As shown in attached picture (MEM to VTT) and highlighted RED, i didnt get this signal on PCB. could you please tell which signal is this and where on Schematic.

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          • #6
            These are the last segments for clock tracks - the segments between last memory and termination resistors.

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