Can one constraint mode be reused with multiple delay corners?
From PDVerse MMMC Interview Masterclass · pdVerse Mentor Series
Direct answer
Yes, and it usually should be. A constraint mode captures timing intent for one behavior (say, functional mode), and that same intent commonly needs to be checked against several different physical conditions — so it gets paired with several different delay corners to build several different views.
Mentor explanation
This is one of the places where the object-based design of MMMC really pays off. You don't want to rewrite your functional SDC three times just because you need to check it at a slow corner, a fast corner, and a typical corner. Instead, you write the constraint mode once and reuse it, pairing it with DC_A, DC_B, and DC_C to build VIEW_A, VIEW_B, and VIEW_C. The reuse isn't just convenient — it also guarantees the timing intent is identical across all three views, so any difference you see in the results is coming from the physical condition, not from an accidental difference in constraints.
Example or conceptual chain
CM_FUNC paired with DC_A, DC_B, and DC_C creates VIEW_A, VIEW_B, and VIEW_C with identical intent under different physical conditions.
Key takeaways
- Yes, and it usually should be.
- A constraint mode captures timing intent for one behavior (say, functional mode), and that same intent commonly needs to be checked against several different physical conditions — so it gets paired with several different delay corners to build several different views.
Self-check: can you answer this aloud?
Try a 45-second answer using this structure:
- State the direct answer.
- Explain the timing or physical reason.
- Name one caveat.
- Say how you would verify it in a real flow.
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