An apparatus for determining relative positioning of first and second objects being relatively movable may include a laser source carried by the first object for generating a source laser beam toward the second object, and a target optical element carried by the second object for generating a first reflected beam and a second diverging reflected beam from the source laser beam. The device comprises a look-up table for providing a first variable m and a second variable J satisfying the equation N=2m\xd7J; and an address generator for generating a read address depending on the first and second variables m and J provided from the look-up table. The first memory cell may be connected to a bit line and a complementary bit line. The modular power system is also low profile for ease of maintenance. Completion status of the data write is requested from the IO controller by a processing unit. An insert portion of the terminal cover layer is formed between an upper surface of the terminal portion and a lower surface of the end of the cover insulating layer.