Virtual Workshop: Constraint Management

Duration: 15 Minutes| Version Required: 17.4

With designs becoming more complex and project timelines shortening, it is essential to find ways to enhance the design process. Embedded rules and constraints allow design intent to be conveyed clearly, reducing overall confusion amongst various stakeholders. Constraint Manager for OrCAD helps to ensure design intent is adhered to throughout the PCB design process. Designers can now easily embed design constraints directly into the OrCAD platform, this allows designers the ability to constrain a design with a process that is fast and efficient.

This document is intended to provide step by step instructions on the constraint manager using OrCAD PCB Designer Professional. For this workshop, download the design files and use the provided design, ConstraintManagement_Start.BRD, to follow along. To view the completed design, select ConstraintManagement_Finish.BRD.

 

1. Open the provided design, ConstraintManagement_Start.BRD, in OrCAD PCB Designer Professional.

2. Select Route > Connect from the menu (F3).

3. Select Pin U2A5.AR13 (Net M_BS<2>).

4. Right Click and select Neck Mode. Click to place the trace.

Note: The trace will be displayed in white during routing when placement is in violation of a constraint.

5. Right click and choose Done (F6).

Note: DRC Errors are flagged with DRC Markers when trace placement is in violation of a constraint.

6. View the DRC errors. Mouse over the DRC Marker to view more information.

7. Select Undo from the toolbar to delete the trace (CTRL-Z).

8. Select Route > Connect from the menu (F3).

9. In the Options Tab, select Bubble > Hug Only.

10. Select Pin U2A5.AR13 (Net M_BS<2>).

11. Right Click and select Neck Mode.

12. Click to place the trace.

13. Right Click and select off Neck Mode.

14. Click to place the trace.

15. Right Click and select Next (CTRL-F2).

16. Click Pin U2A5.AN11 (Net M_CKE<0>).

17. Right click and select Neck Mode.

18. Right click and select Scribble Mode.

19. Move mouse to scribble trace.

20. Click to place.

21. Right click and select off Neck Mode.

22. Move mouse to scribble trace. Click to place.

23. Right click and select off Scribble Mode.

24. Right click and select Next (CTRL+F2).

25. Click and drag to select both traces to route at the same time.

26. Click to place.

27. Right click and select Single Trace Mode to route one trace at a time.

Note: To change the selected trace, right click and select Change Control Trace. Select the desired trace.

28. Click to place and complete the trace.

29. Complete the routing of both traces.

30. Right click and select Done (F6).

31. Select Set Up > Constraints from the menu.

32. In the Worksheet Selector, select Physical Worksheet > Physical Constraint Set > All Layers.

33. Right click in the Constraint Manager Window and select Create > Physical CSet.

34. Name the Physical CSet DIFF_90OHM. Click OK.

35. Enter the information below to create the Constraint Set:

Constraint	Value
Line Width Min	4.0
Line Width Max	4.0
Neck Min	4.0
Neck Max	500.0
Min Line Spacing	0
Primary Gap	6.0
Neck Gap	0
(+) Tolerance	0.01
(-) Tolerance	0.01
Vias	VIA20-10-28_SMB: VIA19-10-28_SMB:C56P38
BB Via Min	5.0
BB Via Max	0.0
Pad-Pad Connect	ALL_ALLOWED
Etch	True
TS	ANYWHERE

 

36. In the Worksheet Selector, select Physical > Net > All Layers.

 

37. Assign DIFF_90OHM to the following differential pairs in the Referenced Physical CSet column:
    • DP_REF1
    • DP_RSVD1
    • DP_RSVD2
    • DP_RSVD3
    • DP_RSVD4
    • DP_RSVD5

 

Note: Use the SHIFT key on the keyboard to select all the differential pairs at once.

 

Conveying your design intent clearly doesn’t have to be a complicated task. OrCAD helps to simplify this process by allowing you to quickly and easily embed design constraints within the OrCAD platform. 

If you would like more tutorials, visit our walk-through page to view additional OrCAD and PSpice video tutorials and download design files.

Don't have OrCAD 17.4? Download the Trial Now

 

Bonus: Configuring a Routing Shortcut

To route more quickly, set function keys for frequently used commands.

 

1. Select Display > Windows> Command from the menu.

 

 

2. To find a specific command, type scriptmode +e in the command window. Press Enter on the keyboard.

 

Note: This will display the command text for the actions performed in OrCAD PCB Designer in the command window.

 

3. Select Route > Connect from the menu (F3).

 

4. Select a net. Right click and select Neck Mode.

5. View the Command Window to determine the corresponding command text.

 

Note: The following commands are frequently used in the Constraint Management Workshop:

Add Connect: add connect

Neck Mode: pop neck

Scribble: pop dyn_option_select ‘@:@Scribble Mode’

 

 

6. In the Command Window, type Funckey n pop neck. Press Enter on the keyboard.

 

Note: This will assign Neck Mode to key ‘N’ on the keyboard. When routing press ‘N’ of the keyboard rather than right clicking and selecting Neck Mode.

 

7. Select Route > Connect from the menu (F3).

 

 

8. Select a net. Press ‘N’ on the keyboard to enter Neck Mode.

Note: This process can be used to assign a keyboard key to any command in OrCAD PCB Designer. Type the desired command in the command window using the following format: Funckey (key) (command).

To assign commands for use in every PCB design and for more information assigning function keys, refer to our video: Assigning Function Keys.