What is the purpose of the pre-floorplan sanity gate?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
It decides whether the imported, linked logical design and its timing intent are trustworthy enough to begin floorplanning; it does not judge placement or timing quality-of-results.
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 design imports cleanly but missing clocks or unresolved references make later analysis incomplete. • Inspect: Start with one named object in the report and trace it to the netlist, library, or SDC statement that created it. • Correct: Stop before floorplanning, correct the owning input or setup, reopen a clean checkpoint, and repeat the same evidence set.
Command Checks & Actions
• check_design -checks {netlist unbound dp_pre_floorplan}: runs the selected design-readiness checks
• check_timing: finds missing or inconsistent timing setup
Run the commands in order. Each line answers a separate part of the check.Healthy, Suspicious & Hard-stop Results
• Expected: It decides whether the imported, linked logical design and its timing intent are trustworthy enough to begin floorplanning; it does not judge placement or timing quality-of-results. • Investigate: The design imports cleanly but missing clocks or unresolved references make later analysis incomplete. • Stop before floorplanning when required logic or timing coverage is missing or unexplained. Stop before floorplanning, correct the owning input or setup, reopen a clean checkpoint, and repeat the same evidence set.
Common Mistake
Do not assume the check passed just because ICC2 continued: The design imports cleanly but missing clocks or unresolved references make later analysis incomplete. 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 design imports cleanly but missing clocks or unresolved references make later analysis incomplete.
Practical Example
Symptom: The design imports cleanly but missing clocks or unresolved references make later analysis incomplete. Corrective path: Stop before floorplanning, correct the owning input or setup, reopen a clean checkpoint, and repeat the same evidence set.
Continue practising