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Registered: ‎02-18-2013

Reconfigure Xilinx FFT 9.1


I want to use a XFFT IP core to do a forward and a backward FFT. The configuration of the FFT core is done via FIFO and the data are send via DMA.


With my current code I can´t configure the FFT direction during runtime. I can set the direction for the first run (Forward and Backward) and the FFT is calculated successfull, but I cannot change the direction. Please take a look at the output for this code.

I want to compute a forward FFT in the first run. So I generate the data (sine wave) and run the FFT. The result is correct. In the second run I want to compute a backward FFT. So I generate samples for a cosine and run the FFT again, but the results aren´t correct now. The same error occurs, when I compute the backward FFT first and then the forward FFT.
So why isn´t the FFT core configured successfull for the second run? I attached my code to this post.

1 Reply
Xilinx Employee
Xilinx Employee
Registered: ‎09-18-2018

Hi @kampi 

Can you please check the configuration channel. The configuration channel carries the Fwd_inv information for the FFT block and this needs to be applied to the Configuration channel before or with the first data sample for the new frame is applied to the FFT core. If this requirement is not met then the core will pick the last successful configuration and process the new fram with that configuration.

Please refer page 67 of PG109 (may22,2019) which explains how the configuration needs to be applied.

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