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Altera_Forum's avatar
Altera_Forum
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13 years ago

FFT Megacore source_valid problem

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

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    13 years ago

    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.

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    13 years ago

    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????