An erase operation for a flash memory device includes identifying a sector group including a plurality of sectors based on an address, simultaneously pre-programming the sectors in the sector group, simultaneously erasing the sectors the sector group, and simultaneously post-programming the sectors in the sector group. A threaded top ring of the fastening assembly relative to a threaded annular seat is screwed reversely to push an anti-leakage washer of the drain pipe upward, so that the threaded top ring and a washer are against the bottom of the wash basin and resilient portions of the resilient ring engages with a non-slip portion of the drain pipe. The second outward face is spaced from a wheel face when the center piece and outer piece are together coupled to the wheel and substantially flush with the wheel face when the center piece is coupled directly to the wheel. In some embodiments, the controller assigns priority to some components requesting access, and assigns a specific page in a memory bank to the priority component.