A negative output minimum delay appears. Is it automatically wrong?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
No; the sign can follow the receiving interface hold convention, but it must be derived and associated with the correct clock and edge.
Technical Explanation
Treat this as a readiness check. It should produce named objects and a result that another engineer can repeat from the same handoff.
What To Check
• Warning sign: An engineer changes the sign only to make hold reports look familiar. • Inspect: Keep at least two possible causes open, then use one named object and the active mode or scenario to separate them. • Correct: Return to the interface equation and STA owner, preserve justified sign intent, and inspect the boundary min path.
Command Checks & Actions
• report_ports -output_delay [get_ports *]: shows boundary constraints and electrical assumptions
• report_timing -delay_type min -to <output_port>: shows a path and its timing calculation
Run the commands in order. Each line answers a separate part of the check.Healthy, Suspicious & Hard-stop Results
• Expected: No; the sign can follow the receiving interface hold convention, but it must be derived and associated with the correct clock and edge. • Investigate: An engineer changes the sign only to make hold reports look familiar. • Stop before floorplanning when required logic or timing coverage is missing or unexplained. Return to the interface equation and STA owner, preserve justified sign intent, and inspect the boundary min path.
Common Mistake
Do not assume the check passed just because ICC2 continued: An engineer changes the sign only to make hold reports look familiar. 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: An engineer changes the sign only to make hold reports look familiar.
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: Return to the interface equation and STA owner, preserve justified sign intent, and inspect the boundary min path. Then I would reopen the clean checkpoint and rerun the same evidence.”
Practical Example
Symptom: An engineer changes the sign only to make hold reports look familiar. Corrective path: Return to the interface equation and STA owner, preserve justified sign intent, and inspect the boundary min path.
Continue practising