Category 2: Logic - 2025.2 English - UG906

Vivado Design Suite User Guide: Design Analysis and Closure Techniques (UG906)

Document ID
UG906
Release Date
2025-12-10
Version
2025.2 English

Logic characteristics describe the basic path structure:

  • Start Point Pin Primitive and End Point Pin Primitive show the types of the starting and ending cells. Confirm these are expected for your design.
  • Start Point Pin and End Point Pin provide the exact pin locations.
  • Logic Levels and Logical Path summarize path depth and primitive usage.
  • Routes indicate the number of routable nets in the path.

Check for control signals like CLR, PRE, RST, and CE that often appear on high-fanout nets. Paths with DSPs or block RAMs tend to have tighter timing budgets due to longer Clock-to-Q delays.

If you see mostly LUTs in the path, investigate:

  • Why smaller LUTs are used instead of larger LUT6s.
  • Whether constraints like KEEP, DONT_TOUCH, or MARK_DEBUG are limiting synthesis optimization.
  • Whether changing synthesis options or using opt_design -remap can reduce logic depth.

Look at the presence of DSPs or RAMs. Timing is harder to meet when these cells are not registered and are followed by deep logic.