A numerical controlled combination drive tower pumping unit includes a main tower frame, a power system, a drive system, a control system, a balance weight box, a balance weight pull rope, a wire rope wheel, a drive rope, and a wire rope hanger. In one preferred embodiment, a plurality of contact elements are positioned spaced apart from one another in columns. Furthermore, before erasing the NROM array, a pre-programming operation is performed to program every single memory cell of the NROM array to the written state for preventing over-erasing of the memory cells.