SK_GPIO
val = sk_win_read_4(sc, SK_GPIO);
sk_win_write_4(sc, SK_GPIO, val);
v = sk_win_read_4(sc, SK_GPIO);
sk_win_write_4(sc, SK_GPIO, v);
v = sk_win_read_4(sc, SK_GPIO);
sk_win_write_4(sc, SK_GPIO, v);
val = sk_win_read_4(sc, SK_GPIO);
sk_win_write_4(sc, SK_GPIO, val);