5 Replies Latest reply on Jun 24, 2016 6:37 AM by robert.berrington

    How do I create an associated net so I can create a matched length group for tuning?

    robert.berrington

      I have a design where a bus of signals pass through a isolator and SSR to a connector. We want to eliminate any skew not associated with the isolator.

       

      Currently we set up each section (connector-to-buffer | buffer-to-SSR | SSR-to-connector) of pin-pairs as a matched length pin pair group. How do I get PADS to recognize that the electrical net/signal is the continuum from one connector to the other?

        • 1. Re: How do I create an associated net so I can create a matched length group for tuning?
          franz.forstmayr

          I had the same problem once. My problem was, that associated nets have some limitations with non discrete devices. If you want something like a solid state relay, you have to define the several lines as single gates with one input and one output.

          In my case i had an 8 Bit Bus Switcher, but i didn't declare each bit pair as a seperate gate, i had one single gate with 8 inputs and 8 outputs.

          Maybe try to seperate your relay, a single gate for each line.

          I read somewhere that associated nets don't work in integrated flow yet, maybe that's the problem.

          • 2. Re: How do I create an associated net so I can create a matched length group for tuning?
            robert.berrington

            This design is in netlist flow. I'm familiar with setting up gates in the integrated flow, but I'm not sure how to do it in the netlist flow.

            • 3. Re: How do I create an associated net so I can create a matched length group for tuning?
              franz.forstmayr

              Ok, i am working with DxDesigner as Schematic tool, you too i think.

              I think you can setup your gates with the parts property. They must have one single input and output.

              So you have an relay symbol, where you set the property "parts 4".
              The supply/"coil" (i don't know the word for an solid state relay) is drawn on a seperate symbol, you have to link the two symbols with the hetero property.

              The hetero property is the name of the two symbols.
              In my case my busswitcher:

              74xx3245.1
              hetero=74xx3245, 74xx3245_p

              parts=8

              74xx3245_p.1

              hetero=74xx3245, 74xx3245_p

              parts=1 (you can delete this property, default is 1)

               

              The two symbols must have equal properties PKG_TYPE and so on, otherwise the Packager won't pack them into a single REFDES.

               

              On the right side you have some resistor arrays, do you set them up with the parts property?. I think they should be single gates then. With this method i can associate nets over my resistor networks without problems.

              • 4. Re: How do I create an associated net so I can create a matched length group for tuning?
                robert.berrington

                That sounds reasonable ... I'll have to find some time to set this up and try it out.

                 

                I've also used the ORDER property on the part instances to force single gates of a part onto the same packaged RefDes.

                 

                I feel a Mentor "Ideas" coming on ... it seems you should just be able to select the nets, unroutes or pin-pairs, <right-click> and select "Associate Nets" or "Create Associated | Electrical Net" then pop up a box to name it, maybe with a default name so you can change it later in PADS Router (or CES).

                • 5. Re: How do I create an associated net so I can create a matched length group for tuning?
                  robert.berrington

                  I did not try the DxDesigner method. However, I was able to use the PADS Part Type Editor to define multiple Gates and associate Pins to those gates. I was then able to create associated nets, add them to a matched length group, then tune them.

                   

                  It should be noted that I probably didn't set up the Gate | Pin Swap correctly. PADS Layout gave me issues about having no available gates/pins to swap to!

                   

                  Another point to make, this is in a Netlist flow, so linking the DxDesigner Symbol to the PADS Part Type through the interface is NOT supported unless you're in Integrated Flow.

                   

                  Here is the result. I selected two of the nets to show how the different segments picked up the tuning:

                   

                  Now that I better understand how PADS Part Type editor works, I may go back to the DxDesigner method and see if I can't get the setting right to flow directly into the Part Type library during forward annotation ... or convince the company to invest in switching over to the integrated flow!

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