Constraints of the revised design can conflict with the physical data of the reference checkpoint. When conflicts occur, the behavior depends on the constraint used. This is illustrated in the following examples.
LOC Constraint Conflict Example
A constraint assigns a fixed location RAMB36_X0Y0 for a cell cell_A. However in the reference checkpoint reference.dcp, cell_A is placed at RAMB36_X0Y1 and a different cell cell_B is placed at RAMB36_X0Y0.
After running read_checkpoint -incremental reference.dcp, cell_A is placed at RAMB36_X0Y0 and cell_B is unplaced. The cell cell_B is placed during incremental placement.
PBlock Conflict Example
In the reference checkpoint there are no Pblocks, but one has been added to the current run. Where there is a conflict, the placement data from the reference checkpoint is used.