Texas Instruments TMS320C64X Manual de usuario descargar pdf (Pagina 50)

DSP_fft16x16r

4-22

xl1_1 = x6;

xl0_1 = x7;

}

yt2 = xl0_0 + xl1_1;

yt3 = xl1_0 − xl0_1;

yt6 = xl0_0 − xl1_1;

yt7 = xl1_0 + xl0_1;

if (radix == 2)

{

yt7 = xl1_0 − xl0_1;

yt3 = xl1_0 + xl0_1;

}

y0[k] = yt0; y0[k+1] = yt1;

k += n>>1;

y0[k] = yt2; y0[k+1] = yt3;

k += n>>1;

y0[k] = yt4; y0[k+1] = yt5;

k += n>>1;

y0[k] = yt6; y0[k+1] = yt7;

}

Special Requirements

- In-place computation is not allowed.

- nx must be a power of 2 or 4.

- Complex input data x[ ], twiddle factors w[ ], and output array y[ ] must be

double-word aligned.

- Real values are stored in even word, imaginary in odd.

- All data are in short precision or Q.15 format. Allowed input dynamic range

is 16 − (log

(nx)−ceil[log

(nx)−1]).

- Output results are returned in normal order.

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

tw_fft16x16 provided in the directory ‘support\fft’. The scale factor must be

32767.5. The input data must be scaled by 2

(log2(nx)−ceil[log4(nx)−1])

completely prevent overflow.

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Texas Instruments TMS320C64X Manual de usuario Pagina 50