jishuqi

代码说明：

  计数器是数字系统中使用最多的时序电路，它不仅能用于对时钟脉冲计数，还可以用于分频、定时、产生节拍脉冲和脉冲序列以及进行数字运算等。(Counter is the most frequently used sequential circuit in digital system. It can be used not only for counting clock pulses, but also for frequency division, timing, generating beat pulses and pulse sequences, and performing digital operations.)