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Altera_Forum
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16 years ago

Altera FFT simulation

I'm working with Altera streaming 256 point FFT core. I've discovered the errata on the core (V9) rearding mismatch between the Matlab sims and HDL sims and the limit on the input range.

Looking at the FFT User Guide, it tells me that the sink_valid signal must be asserted for the source valid to be asserted (and a valid data output). It also says that the sink_sop and sink_eop must be driven while extracting the final frames of data even if no further valid input data is being supplied.

If I run the Verilog testbench that is generated by the core generator, I see that the above conditions are not met yet the core puts out correct data.

Anybody else run into this? How are others driving the inputs while pulling out the delayed FFT results?

Thanks for any input on this.

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

    Hi all,

    I am using FFT megafunction too for my final year project. The problem i had face is i can't get the output of last FFT block since it's size(eg 7 points) is not same with the previous FFT blocks size (eg 8 points). I had follow the instruction Dynamically changing the FFT Size in the manual but still can't get the output of the last FFT block. Anyone face this problem before or any idea to solve it?

    Here my waveform attached. I had refer to the Figure 3-8 (Dynamically Changing the FFT Size) of FFT megafunction.