Texas Instruments TMS320C64X Manual de usuario descargar pdf (Pagina 65)

DSP_ifft32x32

4-37 C64x+ DSPLIB Reference

The FFT coefficients (twiddle factors) are generated using the program

tw_fft32x32 provided in the directory ‘support\fft’. The scale factor must be

2147483647.5. No scaling is done with the function; thus the input data

must be scaled by 2

log2(nx)

to completely prevent overflow.

Implementation Notes

- Bank Conflicts: No bank conflicts occur.

- Interruptibility: The code is interruptible.

- The routine uses log

(nx) − 1 stages of radix-4 transform and performs

either a radix-2 or radix-4 transform on the last stage depending on nx. If

nx is a power of 4, then this last stage is also a radix-4 transform, otherwise

it is a radix-2 transform.

- See the fft16x16t implementation notes, as similar ideas are used.

Benchmarks Cycles (13*nx/8 + 28) * ceil(log

(nx) − 1) + 6 * nx/4 + 39

Codesize 960 bytes

1 2 ... 60 61 62 63 64 65 66 67 68 69 70 ... 168 169

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Texas Instruments TMS320C64X Manual de usuario Pagina 65