dsp_autocor.h64

来自「dm642函数库」· H64 代码 · 共 121 行

;* ======================================================================== *;
;*  TEXAS INSTRUMENTS, INC.                                                 *;
;*                                                                          *;
;*  DSPLIB  DSP Signal Processing Library                                   *;
;*                                                                          *;
;*      Release:        Revision 1.04b                                      *;
;*      CVS Revision:   1.12    Fri Nov  1 19:10:29 2002 (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.                                    *;
;* ======================================================================== *;
* ========================================================================= *
*   NAME                                                                    *
*       DSP_autocor -- Autocorrelation                                      *
*                                                                           *
*   REVISION DATE                                                           *
*       21-Jan-2002                                                         *
*                                                                           *
*   USAGE                                                                   *
*       This routine has the following C prototype:                         *
*                                                                           *
*       void DSP_autocor                                                    *
*       (                                                                   *
*           short *restrict r,                                              *
*           const short *restrict x,                                        *
*           int          nx,                                                *
*           int          nr                                                 *
*       );                                                                  *
*                                                                           *
*       r[nr]   : Output array                                              *
*       x[nr+nx]: Input array. The first nr elements are assumed to be 0.   *
*                 Must be double-word aligned.                              *
*       nx      : Length of autocorrelation                                 *
*                 Must be a multiple of 8.                                  *
*       nr      : Number of lags                                            *
*                 Must be a multiple of 4.                                  *
*                                                                           *
*   DESCRIPTION                                                             *
*       This routine performs an autocorrelation of an input vector         *
*       x. The length of the autocorrelation is nx samples. Since nr        *
*       such autocorrelations are performed, input vector x needs to be     *
*       of length nx + nr. This produces nr output results which are        *
*       stored in an output array r.                                        *
*                                                                           *
*       The following diagram illustrates how the correlations are          *
*       obtained.                                                           *
*                                                                           *
*       Example for nr=8, nx=24:                                            *
*       0       nr                  nx+nr-1                                 *
*       |-------|----------------------|  <- x[]                            *
*       |       |----------------------|  -> r[0]                           *
*       |      |----------------------|   -> r[1]                           *
*       |     |----------------------|    -> r[2]                           *
*       |    |----------------------|     -> r[3]                           *
*       |   |----------------------|      -> r[4]                           *
*       |  |----------------------|       -> r[5]                           *
*       | |----------------------|        -> r[6]                           *
*                                                                           *
*       Note that x[0] is never used, but is required for padding to make   *
*       x[nr] double-word aligned.                                          *
*                                                                           *
*   TECHNIQUES                                                              *
*       Loop coalescing is implemented and both loops are colesced          *
*       together. Separate copies of inner loop counter are made to         *
*       de-couple input loads and output stores. Double word wide loads     *
*       are used on the input data array.                                   *
*                                                                           *
*   ASSUMPTIONS                                                             *
*       The first nr elements are assumed to be 0.                          *
*       nx is a multiple of 8                                               *
*       nr is a multiple of 4                                               *
*       x[] is double-word aligned                                          *
*       No alignment restrictions on r[]                                    *
*                                                                           *
*   MEMORY NOTE                                                             *
*       No memory bank hits under any conditions.                           *
*       This code is a LITTLE ENDIAN implementation.                        *
*                                                                           *
*   NOTES                                                                   *
*       This code is interrupt tolerant but not interuptible                *
*                                                                           *
*   CYCLES                                                                  *
*       nx*nr/4 + 19                                                        *
*                                                                           *
*       e.g. nx=160, nr=32, cycles=1299                                     *
*                                                                           *
*   CODESIZE                                                                *
*       508 bytes                                                           *
*                                                                           *
* ------------------------------------------------------------------------- *
*             Copyright (c) 2003 Texas Instruments, Incorporated.           *
*                            All Rights Reserved.                           *
* ========================================================================= *

        .global _DSP_autocor

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