Writing to reference point BGnX and BGnY should update the internal PPU registers also inside VBLANK period. fixes #79 Former-commit-id: a5237319ccab1aab023bb05878c81a198310fb21 Former-commit-id: 0c9ce4476111eea46e7372b48af77c862c0d2f6a
Former-commit-id: 1aad71d283f7ec5a0f0328f9b683f51e459ae56f Former-commit-id: 42bb30d300c17bace976d106f6da1aca8c0d7643