Data is transferred on a first port during a current cycle until a predetermined number of bytes less an overshoot value for the first port has been transferred on the first port. The apparatus uses a separable memory so that a deck is unnecessary, allowing small, lightweight constructions, and a compression algorithm results in longer playing time, while readwrite operations robust to noise are achieved. A p+ layer is formed on the second n-type epitaxial layer. The anti-split wood screw thus formed can tap an object through the first thread, cut off the chips generated during tapping through the second thread, and channel out the chips through the third thread without being clogged by the chips, hence can avoid the object from splitting and damaging.