What should an initial floorplan input contain?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
An initial floorplan defines the physical envelope and key constraints within which placement and routing will operate. It can be supplied as DEF or scripts, or generated during the design-planning stage.
Technical Explanation
Typical information includes die/core geometry, legal placement rows and sites, routing tracks, macro positions and orientations, port locations, and relevant placement or routing blockages. A design may also need voltage areas, macro keepouts, bounds, or power-planning constraints carried through other supported mechanisms. Do not assume one DEF contains every aspect of physical intent. Die area is the overall chip or block boundary; core area is the region intended for the core implementation. Standard-cell rows define legal placement locations. Tracks describe a routing grid. Macro orientation matters because it moves pins and can change access to the power and signal networks. Placement and routing blockages restrict different resources and are not interchangeable. In ICC2, inspect the resulting database after import. The supplied guide says read_def is incremental by default: some single-valued constraints are overwritten, while some geometry can accumulate. A new DEF read is therefore not necessarily a clean replacement of old physical intent. Decide whether the flow intends to merge or replace information before importing a revision.
Common Mistake
Equating utilization with total die area occupancy without stating which areas and exclusions are used.
Follow-up Question & Model Response
What if no DEF is supplied? Create and validate a floorplan from approved physical requirements; a pre-existing DEF is not mandatory for every new design.
Practical Example
A memory placed flush against a port edge may leave insufficient channel space for its signal pins. The file can be syntactically valid yet create a routability problem that should be corrected before detailed placement.
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