How do you handle pin placement?

 o   Minimize wire length between pins and the internal logic/macros they connect to.

o   Reduce routing congestion, especially near the block boundary.

o   Align pins logically with connected blocks at the next level of hierarchy.

o   Meet timing requirements for critical interface paths.

o   Ensure routability and avoid pin access issues.

o   Group related signals (e.g., buses) together logically.

 

o   Understand Connectivity: Analyze which internal blocks/macros connect to which I/O pins (using flylines or schematics). Understand connectivity to external blocks at the top level.

o   Consider Top-Level Context: If the block is part of a larger design, align pin locations with the corresponding connections on adjacent blocks or routing channels at the top level to minimize top-level routing detours.

o   Tool Assistance: PnR tools provide features for pin placement:

o    Automatic placement based on connectivity ("snap pins" or similar).

o    Spreading algorithms to distribute pins evenly along edges.

o    Manual placement via GUI or coordinates.

o    Pin editors for detailed ordering and spacing.

o   Refinement & Optimization with iterations based on congestion and timing reports.