RM0020 datasheet(53/69 Pages) STMICROELECTRONICS

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RM0020

Function API

53/69

Algorithm:

Equation 46

for each n from 0 to N-1

Performance: See Section 7 and Table 59.

Example 28. iir_frac16_2nd

#include "libdsp2.h"

/* #pragma and ALIGN macros used to align to 4 bytes */

#ifdef __ghs__

#pragma alignvar (4)

#endif

ALIGN_DCC(4)

short x[256/*+2*/] ALIGN_MWERKS(4); /* +2 to ensure there are 4

bytes of readable memory behind x */

#ifdef __ghs__

#pragma alignvar (4)

#endif

ALIGN_DCC(4)

short y[256] ALIGN_MWERKS(4);

#ifdef __ghs__

#pragma alignvar (4)

#endif

ALIGN_DCC(4)

short s[4] ALIGN_MWERKS(4) = {0,0,0,0};

short c[5]

= {10209,20417,10209,2413,5654};

unsigned short N;

void main(void)

{

/* filter the samples in x with second-order IIR filter, */

/* write result into y */

N = 256;

iir_frac16_2nd(N, x, y, c, s);

}

6.29

iir_frac16_casc - cascade of frac16 second-order IIR filters

Function call:

#define iir_frac16_casc

iir_frac16_casc_c

void iir_frac16_casc_c(unsigned short N, short *x, short *y, short

*c,

short *s, unsigned short m);



xn

 b1

xn 1

–

 b2

xn 2

–

 a1

yn 1

–



–

yn 2

–



–

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