Which constraints belong to modes, corners, scenarios, or the netlist?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
Functional intent commonly belongs to modes, operating-condition/parasitic intent to corners, combined analysis status to scenarios, and design-rule constraints can be netlist-specific.
Technical Explanation
A scenario is the active pairing of a mode and a corner. A name in the database is useful only when the required analyses and constraints are active in it.
What To Check
• Warning sign: A constraint is loaded into a context where required scenarios never see it. • Inspect: Compare one named object across the related reports; the same object should tell a consistent story. • Correct: Inspect the current scenario and reported scenario associations, then reload the constraint into the owning context.
Command Checks & Actions
• report_scenarios: shows the MCMM scenario matrix and analysis status
• current_scenario: confirms the active scenario
Run the commands in order. Each line answers a separate part of the check.Healthy, Suspicious & Hard-stop Results
• Expected: Functional intent commonly belongs to modes, operating-condition/parasitic intent to corners, combined analysis status to scenarios, and design-rule constraints can be netlist-specific. • Investigate: A constraint is loaded into a context where required scenarios never see it. • Stop before floorplanning when required logic or timing coverage is missing or unexplained. Inspect the current scenario and reported scenario associations, then reload the constraint into the owning context.
Common Mistake
Do not assume the check passed just because ICC2 continued: A constraint is loaded into a context where required scenarios never see it. Fix or narrowly justify the named objects, then rerun the same command.
What The Interviewer Is Testing
Be ready to explain why this matters before floorplanning: A constraint is loaded into a context where required scenarios never see it.
Follow-up Question & Model Response
Model response: “I would save the report, inspect one affected object in the correct block and scenario, and make or request this correction: Inspect the current scenario and reported scenario associations, then reload the constraint into the owning context. Then I would reopen the clean checkpoint and rerun the same evidence.”
Practical Example
Symptom: A constraint is loaded into a context where required scenarios never see it. Corrective path: Inspect the current scenario and reported scenario associations, then reload the constraint into the owning context.
Continue practising