Applying Electrical Constraints
Creating constraints isn't enough. We must apply them to specific nets or net classes. Let's apply the DDR2_D0_DIFF
constraint set to the DDR2_DQS0 differential pair. To do that:
1. Select the Electrical > Net > Routing > Differential Pair worksheet.
2. Go to the Referenced Electrical CSet column for the DDR2_DQS0 differential pair (DPr).
3. Click the dropdown item then select that DDR2_D0_DIFF we created earlier.
4. You will know that the constraint set was applied when all three rows are populated with the "DDR2_D0_DIFF" constraint
set name.
5. For Impedance, apply the 50 Ohm impedance Constraint set to nets within the Impedance worksheet. To do this, go to
Electrical > Routing > Impedance > DDR3_DATA (50Ω at 15 %). We will apply this to all our DDR3 Data nets.
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OrCAD X High-Speed Digital Design Guide
