FFT程序，此程序虽然耗逻辑资源很大，但是在接受数据后的第7个时钟沿就可以输出FFT变换后的数据，对要求时延较低的系统可以考虑-FFT procedure, this procedure should not consume a lot of logic resources, but the data in the first seven clock can be output along the FFT transformed data, the requirements of time-de