There are two types of placement in the tools:
- Fixed Placement
- Unfixed Placement
Fixed placement is placement specified by the user through one of the following:
- Hand placement
- An XDC constraint
- Using either IS_LOC_FIXED or IS_BEL_FIXED on a cell object of the design loaded in memory.
Unfixed placement is a placement performed by the implementation tools. By setting 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, where it appears as a simple LOC or BEL constraint.
- Promotes a LOC constraint from unfixed to fixed.
- Promotes a BEL constraint from unfixed to fixed.