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About undocumented signal length

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  • About undocumented signal length

    Hi everyone,

    Sometimes signal length is no more documented.
    For example, I fully designed the differential pair GBE1 and applied length matching.
    I got the information "Signal Length" and everything is OK.
    I am working now on the differential pair GBE0.
    I notice that I lost the information "Signal Length" for GBE1 : it was replaced by "n/a".

    What are the main reasons for such issue ?


  • #2
    Are those nets routed yet? I imagine it will indicate na or something similar if the nets aren't routed.

    Otherwise, it appears all of these nets belong to a net class, but perhaps they don't all belong to a length matching class?

    This sort of thing happened to me more than once when I used X-signals to match trace lengths. I set it all up, tune all of the tracks, then come back to it a couple weeks later an it shows stuff like this instead of the tracks' lengths. I usually have to delete all of the X-signals stuff and set it up again.

    When I asked about this here, Robert said he suspected it happens when the user sets up X-signals, then updates Altium while working on the project, then goes back to use X-signals again.🤷


    • #3
      Those nets are routed and are shown as "na".
      Those nets belong to differential pair class.
      It is disturbing.


      • #4
        I'm done with the routing before adding polygon pours.
        As you can see, the differential pair GBE0 is not documented. GBE1 is documented.


        • #5
          More disturbing, I also notice that both differential pair classes vanish: Ethernet_Diff_0 and Ethernet_Diff_1.
          It is not the first time !


          • #6
            When I go to PCB > Differential Pairs Editor, Average Length is documented for both pairs.
            Longest Signal Length is only documented for Ethernet_Diff_1.


            • #7
              I never fully found out when altium does that. Especially when I open older projects, often this happen ... sometimes helps to redraw the track (or part of the track) but sometimes I can't make it work.