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DSP_fft
4-106
Special Requirements
- In-place computation is not allowed.
- nx must be a power of 4 and 4 ≤ nx ≤ 65536.
- Input x[ ] and output y[ ] are stored on double-word aligned boundaries.
- Input data x[ ] is stored in the order real0, img0, real1, img1, ...
- The FFT coefficients (twiddle factors) must be double-word aligned and
are generated using the program tw_fft16x16 provided in the directory
‘support\fft’.
Implementation Notes
- Bank Conflicts: No bank conflicts occur.
- Interruptibility: The code is interrupt-tolerant but not interruptible.
- Loads input x[ ] and coefficient w[ ] as double words.
- Both loops j and i0 shown in the C code are placed in the inner loop of the
assembly code.
Benchmarks Cycles 1.25 * nx * log
4
(nx) – 0.5 * nx + 23 * log
4
(nx) – 1
Codesize 984 bytes