;* ======================================================================== *;
;* TEXAS INSTRUMENTS, INC. *;
;* *;
;* DSPLIB DSP Signal Processing Library *;
;* *;
;* Release: Version 1.02 *;
;* CVS Revision: 1.5 Fri Mar 22 02:07:52 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 *
* DSP_fir_sym: Symmetric FIR Filter *
* *
* USAGE *
* This routine is C-callable and can be called as: *
* *
* void DSP_fir_sym *
* ( *
* short *restrict x, *
* short *restrict h, *
* short *restrict r, *
* int nh, *
* int nr, *
* int s *
* ); *
* *
* x[nr+2*nh] : Pointer to input array of size nr + 2*nh *
* h[nh+1] : Pointer to coefficient array of size nh + 1 *
* Must be word aligned. *
* r[nr] : Pointer to output array of size nr *
* nh : Number of coefficients. *
* Must be multiple of 8. *
* nr : Number of output samples. *
* Must be multiple of 2. *
* s : Number of insignificant digits to truncate *
* *
* DESCRIPTION *
* This symmetric FIR filter assumes the number of filter *
* coefficients is 2*nh + 1. It operates on 16-bit data with a 40-bit *
* accumulation. The filter computes nr output samples. *
* *
* C CODE *
* void DSP_fir_sym *
* ( *
* short *restrict x, *
* short *restrict h, *
* short *restrict r, *
* int nh, *
* int nr, *
* int s *
* ) *
* { *
* int i, j; *
* long y0; *
* long round = (long) 1 << (s - 1); *
* *
* for (j = 0; j < nr; j++) *
* { *
* y0 = round; *
* *
* for (i = 0; i < nh; i++) *
* y0 += (short) (x[j + i] + x[j + 2 * nh - i]) * h[i]; *
* *
* y0 += x[j + nh] * h[nh]; *
* r[j] = (int) (y0 >> s); *
* } *
* } *
* *
* TECHNIQUES *
* Load word instruction is used to simultaneously load two *
* values from h[] in a single clock cycle. *
* The inner loop is unrolled eight times. *
* The outer loop is unrolled eight times. *
* Both the inner and outer loops are software pipelined. *
* *
* ASSUMPTIONS *
* This code is Little Endian. *
* nh must be a multiple of 8 and >= 8. *
* nr must be a multiple of 2. *
* h[] must be word-aligned. *
* *
* MEMORY NOTE *
* No memory bank hits under any conditions. *
* *
* CYCLES *
* (3 * nh/2 + 10) * nr/2 + 20 *
* For nh=24, nr=42: 986 cycles *
* *
* CODESIZE *
* 416 bytes *
* *
* ------------------------------------------------------------------------- *
* Copyright (c) 2002 Texas Instruments, Incorporated. *
* All Rights Reserved. *
* ========================================================================= *
.global _DSP_fir_sym
* ========================================================================= *
* End of file: dsp_fir_sym.h62 *
* ------------------------------------------------------------------------- *
* Copyright (c) 2002 Texas Instruments, Incorporated. *
* All Rights Reserved. *
* ========================================================================= *