以学习板蜂鸣器和EXT0按键为硬件电路 2、TC0用作计数器 3、程序模块化练习，捆绑编译的应用 4、TC0工作于计数状态，T0引脚上升沿/下降沿将使计数器加1，计数溢出后蜂鸣器 长鸣500ms。信号由按键EXT0产生 -Buzzer and EXT0 to learn key board as the hardware circuit 2, TC0 used as a counter 3, a modular training program, compile the a