4位可逆计数器：将50MHz的时钟进行 分频后的结果作为时钟控制，根据输入进行条件判断，再通过设置一个四位的向量将结果输出，利用数码管显示在实验板上-CNTR 4: will be conducted at 50MHz clock frequency as the clock after the control conditions to determine the basis of inputs, and then set up a four through the results of th