Altium: Repeat blocks with differential pairs

Discussion in 'Digital Circuit Design' started by ebelloli, Sep 30, 2016.

  1. ebelloli

    Thread Starter New Member

    Sep 30, 2016
    2
    0
    Hi everyone, i run into a problem with altium traing to use the funtion repeat. i have a schematic sheet with a CAN bus that i want to repeat, as you may know this bus has a differential pair, and i cant repeat it without the compiler telling me "Missing Negative Net for differential pair [CAN_ISO_N1_6], positive net [CAN_ISO_N1_6]"
    I already checked that the directives are correctly attach, i tried to put them into the sheet, outside the sheet, i tried everything, i think
    does anybody know how to do this?
    i think the error comes from the auto label of the wires, as im repeating a block, the signals are named with "_1", "_2" and that "hides" the "_N" and "_P" directives that are needed to altium to interpret a differential pair.

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  2. Papabravo

    Expert

    Feb 24, 2006
    10,148
    1,791
    This is a really picky point, but CAN is NOT a true differential pair. It is quasi-differential WITH RESPECT TO A COMMON GROUND. This last point is incredibly important because you must allow for the possibility of a GROUND differential between two nodes separated by a long cable eg 500 meters.
     
  3. ebelloli

    Thread Starter New Member

    Sep 30, 2016
    2
    0
    ok thx, i know that, but i need to do this cuz i dont want to repeat sheets, in this case there are only two of them, but in other proyects i have more than that. do you know how to solved this?
     
  4. Papabravo

    Expert

    Feb 24, 2006
    10,148
    1,791
    I think your problem revolves around using a primitive in the Altium package for a differential pair. If I was you I would pretend that a CAN connection was three single ended wires. Two bi-directional signal wires and a ground.
     
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