o Minimize wire length between pins and the internal logic/macros they connect to.
Reduce routing congestion, especially near the block boundary.
Align pins logically with connected blocks at the next level of hierarchy.
Meet timing requirements for critical interface paths.
Ensure routability and avoid pin access issues.
Group related signals (e.g., buses) together logically.
- 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.
- 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.
- Tool Assistance: PnR tools provide features for pin placement:
Automatic placement based on connectivity (“snap pins” or similar).
Spreading algorithms to distribute pins evenly along edges.
Manual placement via GUI or coordinates.
Pin editors for detailed ordering and spacing.
- Refinement & Optimization with iterations based on congestion and timing reports.