Net Groups
Sometimes we need a group of nets that perform a specific function but may have different (or the same) electrical and
physical properties. We call these Net Groups in hardware design.
Net groups can serve various purposes, but for our design, we will use it to match the signal timing for the nets in the same
data group DDR3.DQ0 - DDR3.DQ3.
To achieve the same timing for signals, we create a Matched Group in the Constraint Manager.
Setting Up Length Matching
Length Matching requires choosing the correct pin settings within a Matched Group in the Constraint Manager.
To create a Matched Group:
1. Highlight any group of nets that you need to match in timing. Then you can right click and select Create > Match Group…
2. In the new window, Create Match Group, name the match group according to whatever works for your organization's
naming conventions, but in this case, click on Cancel.
3. We already have those nets in a Match Group in the worksheet (indicated by MGrp) in the Type column on the left-most
column of the worksheet.
29 www.cadence.com
OrCAD X High-Speed Digital Design Guide
