Texas Instruments TMS320C64X manual DSPiir, IIR With 5 Coefficients

DSP_iir

DSP_iir	IIR With 5 Coefficients
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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