Steps:
1. In OrCAD X Presto PCB Editor, open the Constraint Manager using Tools - Constraint Manager.
Tip: As usual we will make a constraint set that holds the rules/constraints, then we apply that constraint set to a net, class,
group or region.
2. Create an electrical constraint set under Electrical > Electrical Constraint Set > Routing > Wiring, and right click on the
project name for DSn.
3. Choose Create > Electrical CSet…
4. Give the ECSet a name and it will be added to the spreadsheet.
5. Once added, enter a desired maximum stub length for the ECSet.
6. For example, let's say you want your stubs to be no more than 8 mils (0.203 mm), so you enter '8 mils' in the rule shown
below for the SPIO_SCK signal constraint set.
7. Now you go to the following location to apply that constraint and stub rule it has.
8. Go to the Net > Routing > Wiring worksheet.
9. Choose from the Referenced Electrical CSet column to set it to your desired net.
10. Notice how the stub length rule applies to the net, with added details like Max, Actual and Margin.
Tip: Use to ensure tight signal integrity, and minimal reflections and antennas.
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OrCAD X High-Speed Digital Design Guide
