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AHD Lesson 9 activity

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  • AHD Lesson 9 activity

    Hi Robert

    I have stopped at Lesson 9 activity.
    I have reached a point that I can not length match anything. there is no space in L3.
    if I move anything then I have to route L8 again. then length match again . and one or two routes completes. but there are more.

    please help me
    thank Click image for larger version  Name:	Untitled.jpg Views:	0 Size:	345.4 KB ID:	16198 you

  • #2
    That is exactly the point of this activity. First, do the lengthening of the branches and do the connection to CPU as the last one. That should help.

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    • #3
      thank you for your response.
      There is no room on L3, I have to move the vias, then the length of branches will change.
      can you guide me?

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      • #4
        There is no really much how to guide you. Once you place the vias, they should not be moved.

        Normally I do preliminary routing between memories, then I do preliminary routing from the CPU and at the point where the tracks cross, that is the place for VIA. Then I do the length matching between memories and then length matching from cpu.

        It's not easy - so what you are experiencing is normal. That is why we do the activity.

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        • #5
          Hi robert
          i choose the expert PCB to route . may be it is too advanced for me.
          i will do my best.
          thank you

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          • #6
            Hi
            I have a problem measuring the length of the track (DRAM_SDCLK01_N)
            Manually measured and Altium metered length are different.

            I hit the Tab button twice and then I press Measure Selected Object .(Hole track is selected including vias).
            Can you guide me where I am wrong? Click image for larger version

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            • #7
              This depends on what Altium version you use. They keep changing it a lot.

              Biggest difference usually is because Altium may calculate the shortest length + the length in VIA. When using measurements with Selections, I believe, that measures length of the segments.

              Very ofthen I trust more the selection measurements (watch out for double segments, length in via and be sure all tracks are connected to the middle points of VIAs and PADS). However for rules you many need to use xSignals which will use the calculated length.

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