How do you debug an off-track or blocked pin?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
Report its layer, side, and offset; compare with the track pattern, preferred direction, blockages, PG shapes, spacing rules, and neighbouring pins.
Technical Explanation
A pin may be on the edge yet have no legal track-centred approach. Use targeted alignment and blocked checks supported by the installed release, then inspect the exact pin shape and nearby resources.
Formula Or Decision Rule
Decision rule: at least one allowed approach must remain after all reservations and spacing rules.
What To Check
• Warning sign: A pin is moved onto a nominal track that is reserved or blocked. • Inspect: choose one affected region, macro, row, pin, path, or net and trace the physical cause. • Correct: Choose a usable track/layer or move the blockage and rerun the same targeted check.
Command Checks & Actions
• check_pin_placement -alignment true -blocked_only true: checks pin-placement legality and access-related conditions
• report_pin_placement -pins <pins> -format {layer side offset}: reports pin layer, side, and offset
Run only the commands needed for this question. Save the report with the floorplan version and analysis context.Healthy, Suspicious & Hard-stop Results
• Healthy: Report its layer, side, and offset; compare with the track pattern, preferred direction, blockages, PG shapes, spacing rules, and neighbouring pins. • Suspicious: A pin is moved onto a nominal track that is reserved or blocked. • Hard stop: required legality or physical feasibility is missing or unexplained. Choose a usable track/layer or move the blockage and rerun the same targeted check.
Common Mistake
Do not hide the symptom with an arbitrary utilisation, halo, channel, blockage, pin move, or die-size change. A pin is moved onto a nominal track that is reserved or blocked.
What The Interviewer Is Testing
The interviewer is testing whether you can connect “How do you debug an off-track or blocked pin?” to measurable physical evidence and an owned correction.
Follow-up Question & Model Response
Follow-up probe: What would make you change your decision? Model response: “I would change it if the same controlled rerun shows that a pin is moved onto a nominal track that is reserved or blocked. I would use the named objects and reports to decide whether to iterate, waive, or return the issue.”
Practical Example
Symptom: A pin is moved onto a nominal track that is reserved or blocked. Corrective path: Choose a usable track/layer or move the blockage and rerun the same targeted check.
Continue practising