What are the main inputs required for physical design?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
Physical design needs connectivity, cell models, process rules, timing requirements, and physical intent. These inputs jointly tell the tool what to build, what resources it can use, where things may go, and how fast the result must operate.
Technical Explanation
A gate-level netlist describes cell instances and their connections. Logical library models describe cell behavior, delay, power, and electrical limits. Physical library views describe cell dimensions, pins, and obstructions. Technology data supplies the manufacturing grid, layer and via definitions, and implementation rules. RC technology models describe how interconnect geometry produces resistance and capacitance. SDC supplies clocks, interface timing, and timing exceptions. Some inputs depend on the design and entry point. A floorplan may arrive as DEF or scripts, or be created during planning. A multivoltage design needs power intent, commonly UPF. A scan-inserted design needs scan-chain information for physical scan optimization. Macros need compatible timing and physical views. Switching activity is useful when activity-dependent power optimization or analysis is planned; it is not a universal prerequisite for reading a netlist. In ICC2, reference libraries commonly use NDM, which packages library information for implementation. A complete handoff is therefore more than a list of extensions: the files must belong to compatible revisions and cover the intended operating scenarios. A successful import does not establish that the design is correctly constrained.
Common Mistake
Saying that every design must start with a routed DEF, SPEF, and GDS. Those may be later-stage outputs or restart inputs.
Follow-up Question & Model Response
What would you inspect first if a file is present but the tool still reports missing data? Check the loaded object and its coverage, not just the filename.
Practical Example
For a small controller, collect controller.v, the approved standard-cell NDMs, process technology data, RC models, and its SDC. Add the SRAM views if it instantiates a memory; add UPF if a domain can shut down. Record which files are supplied and which will be generated.
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