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OrCAD X Constraint Management Guide Part 1

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22. Choose the SCS_USB Spacing Constraint Set, and then it will be applied to the entire group. The constraint mapping is already saved immediately in the Constraint Manager, so there is no need to save the constraints. At this point, however, you should save your design. Here is the impact on what we just did - applying spacing constraints (10 mil or 0.254 mm spacing to the power nets). Impacts: f Even though we may have traces with different physical properties, like the ones in the USB_ALL group (for example, USBC_CC1 and 2 need a 50 Ohm single ended impedance, while other traces do not), we can group them together for any reason, to apply rules on the entire group despite physical and electrical property differences. f The creation of Net Groups bypasses the limitations of only being able to apply physical and electrical properties to some nets at a time and being forced to work within only those rules. f The Net Group now allows us to overcome the limitation of not being able to assign a rule to an entire set of nets regardless of the class they belong to. This is the benefit of Net Groups - more opportunities and ways to organize your constraints to handle most any design. The image below explains graphically how this looks. Venn diagram showing how a net group spans across different domains (Physical, Spacing, Electrical) So the understanding of the Venn diagram is that Net Groups can include Net Classes, Physical, Electrical and Spacing rules and constraints. Net Groups can also apply constraints to various groups. Finally, all rules, groups and classes are found within a constraint region. What is a region? In the next section we will explain constraint regions for PCB design. 17 www.cadence.com Part 1 of 5

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