What should be reviewed after read_sdc applies a file?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
Review errors, warnings, object-resolution messages, overridden constraints, current context, and resulting reports; parsing success is only the first gate.
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: The SDC applies with empty selectors or replaces an earlier clock unexpectedly. • Inspect: Compare one named object across the related reports; the same object should tell a consistent story. • Correct: Fix the source SDC or load context, reopen a clean checkpoint, and reapply once.
Command Checks & Actions
• read_sdc <file.sdc>: parses or applies the timing constraints
• report_clocks: shows clock definitions and relationships
• report_exceptions: shows timing exceptions and their scope
Run the commands in order. Each line answers a separate part of the check.Healthy, Suspicious & Hard-stop Results
• Expected: Review errors, warnings, object-resolution messages, overridden constraints, current context, and resulting reports; parsing success is only the first gate. • Investigate: The SDC applies with empty selectors or replaces an earlier clock unexpectedly. • Stop before floorplanning when required logic or timing coverage is missing or unexplained. Fix the source SDC or load context, reopen a clean checkpoint, and reapply once.
Common Mistake
Do not assume the check passed just because ICC2 continued: The SDC applies with empty selectors or replaces an earlier clock unexpectedly. 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: The SDC applies with empty selectors or replaces an earlier clock unexpectedly.
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: Fix the source SDC or load context, reopen a clean checkpoint, and reapply once. Then I would reopen the clean checkpoint and rerun the same evidence.”
Practical Example
Symptom: The SDC applies with empty selectors or replaces an earlier clock unexpectedly. Corrective path: Fix the source SDC or load context, reopen a clean checkpoint, and reapply once.
Continue practising