Net class philosophy

Making PCB Layouts, Manual routing, Auto-routing, Copper pouring, Updating from Schematic, Manufacturing Output
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Exality
Posts: 81
Joined: 28 Sep 2017, 14:08
Location: Seattle, WA area
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Net class philosophy

#1 Post by Exality » 22 Aug 2018, 15:00

Net classes can be defined in Schematic, but the details are added in Layout. When you Renew Layout From Schematic in Layout, you can choose which version of the net classes to use (Schematic or Layout).

I set up a number of complicated class-to-class clearance relationships in Layout for inner vs outer layers and about 8 different classes, so 16 class-to-class clearances altogether. Now if I Renew From Schematic I must choose the Layout version of the net classes or I lose all that work.

But if I make even a small change in the schematic (quite common during layout), nets can be added, deleted, or changed so the layout net classes are no longer correct. I need to go back through my Layout classes and update them manually (and how do I know which nets are no longer defined in Schematic?). Default net names like "Net 63" have to be traced in the schematic to see which class they belong to.

Needless to say, this is a tedious and error-prone operation. I think all characteristics of net classes should be definable in Schematic, rather than putting that off till Layout. Then net and class changes would happen automatically (for the most part) in Schematic and propagate to Layout.

Is there a way to keep net classes synced between Schematic and Layout without losing the information added in Layout?
Gerrit

Alex
Technical Support
Posts: 3376
Joined: 14 Jun 2010, 06:43

Re: Net class philosophy

#2 Post by Alex » 28 Aug 2018, 03:28

You can perform back annotation in Schematic. That will bring net classes and netlists of each net class from PCB Layout to Schematic. When you complete changes in schematic, renew board from components and select schematic net classes as reference. Net class properties and class-to-class rules should be kept in PCB Layout.

FDA
Posts: 40
Joined: 01 Nov 2017, 10:06

Re: Net class philosophy

#3 Post by FDA » 02 Sep 2018, 02:16

Alex wrote:
28 Aug 2018, 03:28
You can perform back annotation in Schematic. That will bring net classes and netlists of each net class from PCB Layout to Schematic. When you complete changes in schematic, renew board from components and select schematic net classes as reference. Net class properties and class-to-class rules should be kept in PCB Layout.
Why do you think that the properties of classes should be stored in the PCB?
For me, everything should be stored in the Schematic. It's a through design system!
The one who develops the scheme and must ask all the requirements.
The PCB can be developed by another developer!

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