;* ======================================================================== *;
;* TEXAS INSTRUMENTS, INC. *;
;* *;
;* DSPLIB DSP Signal Processing Library *;
;* *;
;* Release: Version 1.02 *;
;* CVS Revision: 1.5 Fri Mar 29 15:47:22 2002 (UTC) *;
;* Snapshot date: 18-Apr-2002 *;
;* *;
;* This library contains proprietary intellectual property of Texas *;
;* Instruments, Inc. The library and its source code are protected by *;
;* various copyrights, and portions may also be protected by patents or *;
;* other legal protections. *;
;* *;
;* This software is licensed for use with Texas Instruments TMS320 *;
;* family DSPs. This license was provided to you prior to installing *;
;* the software. You may review this license by consulting the file *;
;* TI_license.PDF which accompanies the files in this library. *;
;* ------------------------------------------------------------------------ *;
;* Copyright (C) 2002 Texas Instruments, Incorporated. *;
;* All Rights Reserved. *;
;* ======================================================================== *;
* ========================================================================= *
* *
* TEXAS INSTRUMENTS, INC. *
* *
* NAME *
* iir *
* *
* *
* REVISION DATE *
* 11-Feb-2002 *
* *
* USAGE *
* This routine is C callable and can be called as: *
* *
* void DSP_iir *
* ( *
* short *restrict r1, /* Output array (used) */ *
* const short *x, /* Input array */ *
* short *restrict r2, /* Output array (stored) */ *
* const short *h2, /* Filter Coeffs. AR part */ *
* const short *h1, /* Filter Coeffs. FIR part */ *
* int nr /* Number of output samples */ *
* ) *
* *
* 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. The output vector is *
* stored in two locations. This routine is used as a high pass *
* filter in the VSELP vocoder. *
* *
* C CODE *
* void DSP_iir *
* ( *
* short *restrict r1, /* Output array (used) */ *
* const short *x, /* Input array */ *
* short *restrict r2, /* Output array (stored) */ *
* const short *h2, /* Filter Coeffs. AR part */ *
* const short *h1, /* Filter Coeffs. FIR part */ *
* int nr /* Number of output samples */ *
* ) *
* { *
* 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]; *
* } *
* } *
* *
* TECHNIQUES *
* The inner loop is completely unrolled and software pipelined *
* (i.e. each time the 5 cycle loop "LOOP" is executed the inner *
* loop of the C code is executed.) *
* *
* MEMORY NOTE *
* This code is ENDIAN NEUTRAL. *
* This code is interrupt-tolerant but not interruptible. *
* *
* MEMORY NOTE *
* To avoid memory hits r1[] and r2[] must be aligned on the next word *
* boundary following the alignment of x[], e.g.: *
* #pragma DATA_MEM_BANK(x, 0); *
* #pragma DATA_MEM_BANK(r1, 2); *
* #pragma DATA_MEM_BANK(r2, 2); *
* *
* CYCLES *
* 5 * nr + 30 *
* *
* For nr = 40: 230 cycles *
* *
* CODESIZE *
* 384 bytes *
* *
* ------------------------------------------------------------------------- *
* Copyright (c) 2002 Texas Instruments, Incorporated. *
* All Rights Reserved. *
* ========================================================================= *
.global _DSP_iir
* ========================================================================= *
* End of file: dsp_iir.h62 *
* ------------------------------------------------------------------------- *
* Copyright (c) 2002 Texas Instruments, Incorporated. *
* All Rights Reserved. *
* ========================================================================= *