How do you confirm the correct top module and netlist revision?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
The current block, expected top name, hierarchy, and inventory must agree with the handoff record and synthesis summary.
Technical Explanation
The top module is the design boundary ICC2 believes it is working on. If it is wrong, every later count and report can look reasonable for the wrong design.
What To Check
• Warning sign: Reports look plausible but describe an older top or a sibling block. • Inspect: Start with one named object in the report and trace it to the netlist, library, or SDC statement that created it. • Correct: Open and select the approved block, then repeat identity and inventory checks before applying constraints.
Command Checks & Actions
• current_block: confirms the active design block
• get_blocks *: lists available design blocks
• sizeof_collection [get_cells -hierarchical *]: counts exactly the objects returned by a selector
Run the commands in order. Each line answers a separate part of the check.Healthy, Suspicious & Hard-stop Results
• Expected: The current block, expected top name, hierarchy, and inventory must agree with the handoff record and synthesis summary. • Investigate: Reports look plausible but describe an older top or a sibling block. • Stop before floorplanning when required logic or timing coverage is missing or unexplained. Open and select the approved block, then repeat identity and inventory checks before applying constraints.
Common Mistake
Do not assume the check passed just because ICC2 continued: Reports look plausible but describe an older top or a sibling block. 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: Reports look plausible but describe an older top or a sibling block.
Practical Example
Symptom: Reports look plausible but describe an older top or a sibling block. Corrective path: Open and select the approved block, then repeat identity and inventory checks before applying constraints.
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