Texas Instruments TMS320C64X Manual de usuario descargar pdf (Pagina 82)

DSP_iir

4-54

IIR With 5 Coefficients

DSP_iir

Function void DSP_iir (short * restrict r1, const short * restrict x, short * restrict r2, const

short * restrict h2, const short * restrict h1, int nr)

Arguments r1[nr+4] Output array (used in actual computation. First four elements

must have the previous outputs.)

x[nr+4] Input array

r2[nr] Output array (stored)

h2[5] Moving-average filter coefficients

h1[5] Auto-regressive filter coefficients. h1[0] is not used.

nr Number of output samples. Must be ≥ 8.

Description The IIR performs an auto-regressive moving-average (ARMA) filter with 4

auto-regressive filter coefficients and 5 moving-average filter coefficients for

nr output samples.

Algorithm This is the C equivalent of the assembly code without restrictions. Note that

the assembly code is hand optimized and restrictions may apply.

void DSP_iir(short *r1, short *x, short *r2, short *h2,

short *h1, int nr)

{

int j,i;

int sum;

for (i=0; i<nr; i++){

sum = h2[0] * x[4+i];

for (j = 1; j <= 4; j++)

sum += h2[j]*x[4+i−j]−h1[j]*r1[4+i−j];

r1[4+i] = (sum >> 15);

r2[i] = r1[4+i];

}

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Texas Instruments TMS320C64X Manual de usuario Pagina 82