How do you plan boundary cells around rows and voltage areas?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
Select library-approved left, right, top, bottom, inside-corner, and outside-corner cells for the actual row and voltage-area geometry, then report rules before insertion.
Technical Explanation
Boundary cells complete physical edges; they do not repair an invalid core or substitute for taps and fillers. Row orientation, notches, multiple voltage areas, and macro boundaries can require different cells and orientations.
Formula Or Decision Rule
Decision rule: every exposed row or voltage-area edge has the correct library-specific boundary treatment.
What To Check
• Warning sign: Cells are missing at inside corners or inserted with a mismatched orientation. • Inspect: choose one affected region, macro, row, pin, path, or net and trace the physical cause. • Correct: Correct the rule or geometry, compile deliberately, and run the applicable boundary/floorplan checks.
Command Checks & Actions
• set_boundary_cell_rules -left_boundary_cell <lib_cell> -right_boundary_cell <lib_cell>: defines library-specific boundary-cell choices
• report_boundary_cell_rules: reports the active boundary-cell rules
• compile_boundary_cells -voltage_area <voltage_area>: inserts boundary cells using the active rules; this command is deprecated in the referenced release, so verify the project-approved targeted replacement
Run only the commands needed for this question. Save the report with the floorplan version and analysis context.Healthy, Suspicious & Hard-stop Results
• Healthy: Select library-approved left, right, top, bottom, inside-corner, and outside-corner cells for the actual row and voltage-area geometry, then report rules before insertion. • Suspicious: Cells are missing at inside corners or inserted with a mismatched orientation. • Hard stop: required legality or physical feasibility is missing or unexplained. Correct the rule or geometry, compile deliberately, and run the applicable boundary/floorplan checks.
Common Mistake
Do not hide the symptom with an arbitrary utilisation, halo, channel, blockage, pin move, or die-size change. Cells are missing at inside corners or inserted with a mismatched orientation.
What The Interviewer Is Testing
The interviewer is testing whether you can connect “How do you plan boundary cells around rows and voltage areas?” 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 cells are missing at inside corners or inserted with a mismatched orientation. I would use the named objects and reports to decide whether to iterate, waive, or return the issue.”
Practical Example
Symptom: Cells are missing at inside corners or inserted with a mismatched orientation. Corrective path: Correct the rule or geometry, compile deliberately, and run the applicable boundary/floorplan checks.
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