用定时器 3来改变小灯的状态，T3每发生 200次中断小灯改变状态一次。1 个 LED灯常亮，

1 个 LED灯闪烁。 -3 with a timer to change the status of small lights, T3 occurred 200 times for every little light to change the status of an interrupt. 1 LED lights lit, an LED flashes.