Placement blockage
Beginner
An area marked “no parts here” (or “only a few parts here”) to keep space free for wires.
Novice
An area where the placer may not put cells. A hard blockage allows none. A soft blockage is kept empty during the main placement, but cells added later for timing or for the clock may use it. A partial blockage lets cells fill only a set percentage of the area.
Expert
DEF BLOCKAGES with PLACEMENT (hard), PLACEMENT + SOFT, or PLACEMENT + PARTIAL maxDensity. Typical uses: macro channels, notches, areas over sensitive analog, and partial blockages to thin out predicted congestion hot spots.
Explained in Placement (Design Flow).
See also: Halo (keep-out margin), Region, guide and fence.