Placement Types - Placement Types - 2026.1 English - UG903

Vivado Design Suite User Guide: Using Constraints (UG903)
Document ID
UG903
Release Date
2026-07-01
Version
2026.1 English

The tools support two types of placement:

  • Fixed Placement
  • Unfixed Placement

Fixed Placement

Do the following to define fixed placement:

  • Hand placement
  • An XDC constraint
  • Using IS_LOC_FIXED or IS_BEL_FIXED on a cell object of the design loaded in memory.

Unfixed Placement

The implementation tools perform unfixed placement. When you set the placement as fixed, the implementation cannot move the constrained cells during the next iteration or during an incremental run. A fixed placement is saved in the XDC file as a simple LOC or BEL constraint.

IS_LOC_FIXED
Promotes a LOC constraint from unfixed to fixed.
IS_BEL_FIXED
Promotes a BEL constraint from unfixed to fixed.