@Abdallah Salah SDC is not the correct approach here. As I've informed you over email, the Synthesis step does not read SDC files. There are two variables: SYNTH_EXCLUDED_CELL_FILE PNR_EXCLUDED_CELL_FILE These are lists of cells to be excluded. Provide empty files if you want to enable the use of all library cells. However, some of these cells are excluded due to exceedingly bad timing characteristics and/or DRC issues. We don't recommend messing with these lists unless you're sure what you're doing (in fact, the direction we're heading in is to ignore more cells.)