dsp_fir_gen.h64

来自「dm642函数库」· H64 代码 · 共 129 行

;* ======================================================================== *;
;*  TEXAS INSTRUMENTS, INC.                                                 *;
;*                                                                          *;
;*  DSPLIB  DSP Signal Processing Library                                   *;
;*                                                                          *;
;*      Release:        Revision 1.04b                                      *;
;*      CVS Revision:   1.14    Thu Jun 12 17:41:04 2003 (UTC)              *;
;*      Snapshot date:  23-Oct-2003                                         *;
;*                                                                          *;
;*  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) 2003 Texas Instruments, Incorporated.             *;
;*                          All Rights Reserved.                            *;
;* ======================================================================== *;
;* ======================================================================== *;
;*  Assembler compatibility shim for assembling 4.30 and later code on      *;
;*  tools prior to 4.30.                                                    *;
;* ======================================================================== *;
;* ======================================================================== *;
;*  End of assembler compatibility shim.                                    *;
;* ======================================================================== *;
* ========================================================================= *
*                                                                           *
*   TEXAS INSTRUMENTS, INC.                                                 *
*                                                                           *
*   NAME                                                                    *
*       DSP_fir_gen: FIR Filter (general purpose)                           *
*                                                                           *
*   USAGE                                                                   *
*       This routine is C-callable and can be called as:                    *
*                                                                           *
*       void DSP_fir_gen                                                    *
*       (                                                                   *
*           const short *restrict x,  /* Input ('nr + nh - 1' samples) */   *
*           const short *restrict h,  /* Filter coefficients (nh taps) */   *
*           short       *restrict r,  /* Output array ('nr' samples)   */   *
*           int                   nh, /* Length of filter (nh >= 5)    */   *
*           int                   nr  /* Length of output (nr >= 1)    */   *
*       );                                                                  *
*                                                                           *
*   C CODE                                                                  *
*                                                                           *
*       This is the C equivalent of the assembly code. Note that the        *
*       assembly code is hand optimized and restrictions may apply.         *
*                                                                           *
*       void DSP_fir_gen                                                    *
*       (                                                                   *
*           const short *restrict x,  /* Input ('nr + nh - 1' samples) */   *
*           const short *restrict h,  /* Filter coefficients (nh taps) */   *
*           short       *restrict r,  /* Output array ('nr' samples)   */   *
*           int                   nh, /* Length of filter (nh >= 5)    */   *
*           int                   nr  /* Length of output (nr >= 1)    */   *
*       )                                                                   *
*       {                                                                   *
*           int i, j, sum;                                                  *
*                                                                           *
*           for (j = 0; j < nr; j++)                                        *
*           {                                                               *
*               sum = 0;                                                    *
*               for (i = 0; i < nh; i++)                                    *
*                   sum += x[i + j] * h[i];                                 *
*                                                                           *
*               r[j] = sum >> 15;                                           *
*           }                                                               *
*       }                                                                   *
*                                                                           *
*   DESCRIPTION                                                             *
*       Computes a real FIR filter (direct-form) using coefficients         *
*       stored in vector h. The real data input is stored in vector x.      *
*       The filter output result is stored in vector r. This FIR            *
*       assumes the number of filter coefficients is greater than or        *
*       equal to 5. It operates on 16-bit data with a 32-bit                *
*       accumulate. This routine has no memory hits regardless of where     *
*       x, h, and r arrays are located in memory. The filter is nr          *
*       output samples and nh coefficients. The assembly routine            *
*       performs 4 output samples at a time.                                *
*                                                                           *
*   TECHNIQUES                                                              *
*       1. Load double word instruction is used to simultaneously load      *
*          four values in a single clock cycle.                             *
*                                                                           *
*       2. The inner loop is unrolled four times and will always            *
*          compute a multiple of 4 of nh and nr. If nh % 4 != 0, the        *
*          code will fill in 0s to make nh a multiple of 4. If nr % 4       *
*          != 0, the code will still perform a mutiple of 4 outputs.        *
*                                                                           *
*       3. Both the inner and outer loops are software pipelined.           *
*                                                                           *
*       4. This code yields best performance when ratio of outer            *
*          loop to inner loop is less than or equal to 4.                   *
*                                                                           *
*   ASSUMPTIONS                                                             *
*       1. Little Endian is assumed for LDNDW.                              *
*       2. nh >= 5.                                                         *
*       3. nr multiple of 4.                                                *
*       4. Output array r[] must be word-aligned                            *
*                                                                           *
*   MEMORY NOTE                                                             *
*       No memory bank hits under any conditions.                           *
*       Little Endian operation is assumed.                                 *
*                                                                           *
*   CYCLES                                                                  *
*       [11 + 4 * ceil(nh/4)] * nr/4 + 15                                   *
*                                                                           *
*   CODESIZE                                                                *
*       544  bytes                                                          *
*                                                                           *
* ------------------------------------------------------------------------- *
*             Copyright (c) 2003 Texas Instruments, Incorporated.           *
*                            All Rights Reserved.                           *
* ========================================================================= *

        .global _DSP_fir_gen

* ========================================================================= *
*   End of file:  dsp_fir_gen.h64                                           *
* ------------------------------------------------------------------------- *
*             Copyright (c) 2003 Texas Instruments, Incorporated.           *
*                            All Rights Reserved.                           *
* ========================================================================= *