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6159 Discussions

FFT Megacore source_valid problem

Honored Contributor II

Hello Altera Professionals!. 


I have a problem with FFT Megacore. 


My system:  

Quartus 11.1sp1 

ModelSim 10c 

Cyclone IV GX 150 


I'm use FFT core in two configurarions (two different instanses): 

1. Floating point FFT, Variable Streaming, 256 points,  


2. Floating point ifft (inverse FFT), 128 points - one half of FFT-256points result. 



I have a problem with inverse FFT. Using FFT Megacore Datasheet, I prepare SOP, EOP, source Ready (constantly '1'), sink_valid changes from '0' to '1' 


In waveforms my problem - IFFT MISS point number 126!!! (source_valid sets to '0' and rise to '1' next clk). WHY? I haven't any errors in FFT error interface. Please, help me 


When I must to deassert sink_valid signal? in rising or falling edge? Now I do it in same time with EOP on rising clk
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2 Replies
Honored Contributor II

I don't see the reset_n signal in your simulation. You must operate this, otherwise you can not be sure of what goes on inside.

Honored Contributor II

I'm making a project under the theme OFDM, but now I'm blocking Regarding the FFT block in Quartus II MegaCore 8.00 but if I can attack my FFT block a signal (NCO) just test output remains unchangeable (real and imaginary) and also I tried with the block of QAM but it does not work and thank you for your help????