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Connections across multiple sheets

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  • Connections across multiple sheets

    Altium designer contains these two tools in its arsenal: "Port" and "Off Sheet Connector".

    Click image for larger version

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    Both of these can be used to make signal connections across the different schematic sheets of a multi-sheet schematic. Until now, I have failed to understand the difference between these and when to use each.

    Is it sufficient to only use Port and not ever need to use Off Sheet Connector? Why do such similar tools exist in Altium Designer for Off-Sheet connections?

  • #2
    Yes, ports are sufficient.
    The off sheet connector may only work in "flat" hierarchy designs, whereas ports work in all.


    • #3
      I have never had to do a hierarchical schematic design. The schematic designs I have seen so far, for FPGA boards, do not indicate that there is a hierarcy. The schematic is flat. It could be more than 50 pages long but is always still flat.

      I have certainly seen the scenario where part of the design is encapsulated into a single block. This block then has I/O ports and then this block is used elsewhere in the schematic to simplify the connections.

      Is hierarchical design done often?

      Besides this, how does one force Altium designer to show the location of the other next where a port or off-sheet connector connects to? I mean, just having net name is not enough right? It also needs to provide some coordinates like "sheet 3, 6D" or something like that.
      Last edited by gyuunyuu1989; 05-24-2023, 02:21 PM.


      • #4
        i have very large FPGA designs 60+ pages and i do not use hierachical designs.. just global netnames. it becomes a hassle when adding nets..
        i use ports and busses to indicate stuff is going together to another page.. but it has no reference in the schematic.

        as an example.
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        i use the page blocks to give structure in the schematic pages tree.. yes this adds pages with blocks but gives a better visual in altium

        Last edited by Paul van Avesaath; 05-25-2023, 04:16 AM.


        • #5
          Is hierarchical design done often?
          It depends on how you look at it. I personally and the company I work for use hierarchical as standard nowadays. But as mentioned by Paul in the previous comment, not everyone does it nor needs it.
          In the past we used flat, but once we needed to repeat/reuse blocks, we changed.
          We also do it as the main page can be like a simple block diagram of the design.

          There are 2 types of repeats where ports are useful:
          - Reuse of blocks from other designs. Either copy/paste sheet or device sheets. Here you may need different names in your 'main' schematic then originally was in the sheet.
          - Repeat a block multiple times and having only one 'design' part. This reduces verification of the design.
          Click image for larger version  Name:	Capture repeating block.png Views:	0 Size:	42.1 KB ID:	21546

          For ports, Altium can automatically add the location of the 'counter' ports to the sheets.


          • #6
            use ports.

            I believe off sheet connectors are just legacy to support Oracd import, but otherwise they are useless.

            Ports have more options, including automatic info about where signal continues. This will help you to answer your question about location of the same port on other pages:

            In this video we talk a lot about hierachical design:


            • #7
              I have seen many FPGA board schematics that used what looked like the off sheet connector in Altium, I am not sure what tool was used to create them. I thought ports are only really useful if we are going to convert a schematic into a block for connection to other blocks using ports and for mere same level hierarchy connections, we use off sheet connectors.


              • #8
                This is a relevant link from the Altium website:


                • #9
                  So did the Altium page answer your question?


                  • #10
                    Robert, answered my question.