采用定时器/计数器T0对外部脉冲进行计数，每计数100个脉冲后，T0转为定时工作方式。定时1ms后，又转为计数方式，如此循环不止。假定MCS-51单片机的晶体振荡器的频率为6MHz，请使用方式1实现(A timer / counter T0 is used to count the external pulse. After counting 100 pulses, T0 turns to a timing operation. After timing 1ms, it turns to cou