Texas Instruments TMS320C64X Manual do Utilizador descarregar pdf (Página 63)

DSP_ifft16x32

4-35 C64x+ DSPLIB Reference

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

tw_fft16x32 provided in the directory ‘support\fft’. The scale factor must be

32767.5. 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 (12.5 * nx/8 + 30) * ceil[log

(nx) − 1] + 6 * nx/4 + 32

Codesize 864 bytes

1 2 ... 58 59 60 61 62 63 64 65 66 67 68 ... 168 169

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Texas Instruments TMS320C64X Manual do Utilizador Página 63