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Why does "Is No Connect" pin property stay asserted if you end up connecting the pin to a net?

Valueduser

I'm working on a tcl script and I figured I could use the "Is No Connect" property to determine whether there was an attached net to a pin only to find out that if the property is set it does not get cleared by subsequently connecting the pin to a net.  So it's possible to have a pin connected to a net and have the "Is No Connect" property asserted.  Is this a bug or is this intentional?  It has led me to question the accuracy of my script and now I need to find another way to pull out the required information.  I'm hoping someone can provide an explanation. 

  • 0

    In Capture, Design Rules Check tool checks for unconnected pins. If we intentionally leave a pin unconnected in a schematic page, it needs a "No Connect" symbol. The Design Rules Check tool ignores unconnected pins with "No Connect" symbols. What I have observed that if a pin with a no connect symbol is connected to a net, the no connect symbol has no effect on the pin and becomes invisible. If the pin is later disconnected from the net, the no connect symbol becomes visible again. Also, unconnected pin with 'No connect' symbol will always have 'Is No Connect' property.

  • 0 in reply to rg13

    That all makes sense.  The problem I was having with my script was that I was getting a part instance -> pin Instance -> net instance but if the pin wasn't connected to a net the script would fail.  I started looking at the no connect property first but got some false positives from pins that were initially marked as no connects but then subsequently connected to the net.  The solution to the problem was to not look at the no connect property but instead just check to see if the pin instance returned a valid net object by seeing if it was NULL or not.  Thanks for the input.

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