FFT IP Core: User Guide

ID 683374
Date 11/06/2017
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3.4.2.6. I/O Order

The I/O order determines order of samples entering and leaving the FFT and also determines if the FFT is operating in engine-only mode or engine with bit-reversal or digit-reversal mode.

If the FFT operates in engine-only mode, the output data is available after approximately N + latency clocks cycles after the first sample was input to the FFT. Latency represents a small latency through the FFT core and depends on the transform size. For engine with bit-reversal mode, the output is available after approximately 2N + latency cycles.

Figure 15. Data Flow—Engine-Only Mode
Figure 16. Data Flow—Engine with Bit-Reversal or Digit-Reversal Mode