功能：由KEY1键使系统进入空闲状态，由定时器0中断唤醒； 由KEY2键使系统进入掉电状态，由KEY3键盘中断唤醒-functions : bonding KEY1 by the system to enter idle state, the timer interruption awaken 0 Key KEY2 by allowing the system to enter the state of restart from the keyboard interrupt awaken KE