How do you audit input-delay min and max completeness?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
For each timed input, confirm reference clock, edge, rise/fall scope, and both early and late interface intent where required.
Technical Explanation
For an input port, min and max describe the earliest and latest external arrival. Both must point to the correct reference clock and edge.
What To Check
• Warning sign: Only max delay exists, so setup is analysed while hold coverage is incomplete. • Inspect: Compare one named object across the related reports; the same object should tell a consistent story. • Correct: Return to the interface budget and add the missing intentional cases; do not duplicate max blindly as min.
Command Checks & Actions
• report_ports -input_delay [get_ports *]: shows boundary constraints and electrical assumptions
• check_timing: finds missing or inconsistent timing setup
Run the commands in order. Each line answers a separate part of the check.Healthy, Suspicious & Hard-stop Results
• Expected: For each timed input, confirm reference clock, edge, rise/fall scope, and both early and late interface intent where required. • Investigate: Only max delay exists, so setup is analysed while hold coverage is incomplete. • Stop before floorplanning when required logic or timing coverage is missing or unexplained. Return to the interface budget and add the missing intentional cases; do not duplicate max blindly as min.
Common Mistake
Do not assume the check passed just because ICC2 continued: Only max delay exists, so setup is analysed while hold coverage is incomplete. 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: Only max delay exists, so setup is analysed while hold coverage is incomplete.
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 budget and add the missing intentional cases; do not duplicate max blindly as min. Then I would reopen the clean checkpoint and rerun the same evidence.”
Practical Example
Symptom: Only max delay exists, so setup is analysed while hold coverage is incomplete. Corrective path: Return to the interface budget and add the missing intentional cases; do not duplicate max blindly as min.
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