说明：  在数字电路中，常需要对较高频率的时钟进行分频操作，得到较低频率的时钟信号。我们知道，在硬件电路设计中时钟信号时非常重要的。
(in digital circuits, the need for regular high frequency clock operating frequency for hours, a lower frequency of the clock signal. We know that the hardware circuit design clock signal is very important.)