How do pitch, offset, direction, and width define routing tracks?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
Pitch controls repetition, offset sets the first coordinate, direction selects X or Y track lines, and width can reserve a wire width. Technology rules decide legality.
Technical Explanation
Two patterns with the same pitch can be shifted and therefore offer different pin access. Compare preferred layer direction, nominal and usable tracks, spacing, blockages, wide-wire needs, and macro/pin geometry.
Formula Or Decision Rule
Track coordinate = offset + k x pitch, where k is an integer.
What To Check
• Warning sign: Tracks exist but do not cross the core or miss all important pins. • Inspect: choose one affected region, macro, row, pin, path, or net and trace the physical cause. • Correct: Correct the technology or project track definition and rerun floorplan and pin checks.
Command Checks & Actions
• create_track -layer <layer> -space <pitch> -coord <offset> -width <width> -dir <X_or_Y>: creates a routing-track pattern
• report_design -floorplan: reports the floorplan state understood by the tool
Run only the commands needed for this question. Save the report with the floorplan version and analysis context.Healthy, Suspicious & Hard-stop Results
• Healthy: Pitch controls repetition, offset sets the first coordinate, direction selects X or Y track lines, and width can reserve a wire width. Technology rules decide legality. • Suspicious: Tracks exist but do not cross the core or miss all important pins. • Hard stop: required legality or physical feasibility is missing or unexplained. Correct the technology or project track definition and rerun floorplan and pin checks.
Common Mistake
Do not hide the symptom with an arbitrary utilisation, halo, channel, blockage, pin move, or die-size change. Tracks exist but do not cross the core or miss all important pins.
What The Interviewer Is Testing
The interviewer is testing whether you can connect “How do pitch, offset, direction, and width define routing tracks?” 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 tracks exist but do not cross the core or miss all important pins. I would use the named objects and reports to decide whether to iterate, waive, or return the issue.”
Practical Example
Symptom: Tracks exist but do not cross the core or miss all important pins. Corrective path: Correct the technology or project track definition and rerun floorplan and pin checks.
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