并串转换器：将并行输入的信号以串行方式输出，这里要注意需先对时钟进行分频，用得到的低频信号控制时序，有利于观察结果（可以通过L灯观察结果）-And series converter: the input signal in parallel to serial output, where attention should be paid to the need to carry out first clock frequency, low-frequency signals received b