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Honored Contributor I

FFT Megacore Problem


I'm a beginner of DSP builder.I am doing a fft work with the fft megacore V7.2.During  

my work,I got some problems.I wanna your help. 


My problem: 

1.I use the streaming mode to do fft.But my frame was not continuous,there are spaces  

between the frames(space was set to zero).So the sink_valid signal asserted  

simultaneously with the sink_sop asserted and de-asserted with sink_eop asserted.But the  

result seem not correct(the source_valid,source_sop and source_eop).If the frame was  

continuous(the sink_valid is set to high always),there was no wrong.So does this mean the  

streaming mode can only accept continuous frame? 


2.i changed the mode to variable streaming mode,the result seems right,but the source_sop  

changed always one clock later than the source_valid.Is this right?(source_eop was right) 


3.If the FFT output in the variable streaming mode was right,how can i generate the input control signals of IFFT(sink_valid,sink_sop,sink_eop)?Because the source_sop and source_valid doesn't change(asserted/deasserted) at the same time,so I can't use them for the IFFT input signal.  


4.If I send only one frame to the fft core,there is no result(I have run simulate long  

enough).Is this a bug of FFT in version 7.2?The user guide does not say that the fft core  

should receive more than one frame. 


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