P1.0输出1HZ方波，送入计数器T0，计的数通过数码管的方式显示出来，最多显示到99，超过以后重新回到0。

P1.0 outputs a 1HZ square wave and sends it to the counter T0. The number of the meter is displayed by the digital tube, and it is displayed up to 99. When it is over, it will return to 0.