_cpu_spin
void _cpu_spin(uint32_t); /* for delay loop. */
_cpu_spin(1); /* load function on cache. */
_cpu_spin(10000000);
_cpu_spin(1); /* load function on cache. */
_cpu_spin(cnt_1s); /* 1 sec. */
_cpu_spin(sh_clock.cpucycle_1us * n);