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Altera_Forum's avatar
Altera_Forum
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15 years ago

fft RELATED

HI EVERY ONE

I am using FFT mega Core for performing the 1024 point FFT.

Input (real data only) data to FFT core i am reading for a memory and within 40 micro sec reading should be completed because after 40 micro sec new data has to be write in same memory and next time i can only read after 40 micro sec.

so i am using the burst mode of I/O data flow for the FFT core.

but input data to fft core is not synchronize with sink_ready because sink_ready complete cycle finish after 40 micro sec and with some clock rate it is matching but that clock rate is difficult to generate in my application.

With 70 MHz clock sink_ready is completed around 37 micro sec and sink_ready become high before 40 micro sec but my input data will come after 40 micro sec only.

if by any way i have control on sink_ready to increase the OFF time(when sink_ready is low) without changing the ON time(when sink_ready is high) then my problem will be solve.

so is there any method to control the sink_ready as per my requirement with the help of sink_valid or any other in way. i do not have so much flexibility to change the clock but we can adjust our clock up to certain extend.

plz

help me

with regard

Altera user

1 Reply

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

    For any case of block based data processing (e.g. 1024 fft) you can keep the signal streaming by having two input buffers each 1024 size.

    You read 1024 data into fft while receiving next 1024 input samples in a second buffer. You switch outputs as required:

    state1: write input to buffer1, write from buffer2 to fft, read out fft

    state2: write input to buffer2, write from buffer1 to fft, read out fft

    It may be the altera fft streaming means this mode anyway, find out.