iircas4.asm

四阶无限长冲激响应滤波器的DSP ccs环境下的实现

;***********************************************************
; Version 2.20.02                                           
;***********************************************************
;  Function:	 iircas4
;  Description:  cascaded IIR direct form II using 4-coefs per biquad
;
;  Copyright Texas instruments Inc, 1999
;-----------------------------------------------------------------------------
; Revision History:
; 1.00  T. Horner, 2/15/00. Original version. Started from code by Rosemarie 
;   Piedra, Greg Peake, and Karim Djafarian.
; 1.01  Li Yuan, 6/13/00. Fixed pop up order error.
; 2.00  C. Iovescu, 5/20/02 Modified implementation to use Dual Mac
; 2.10 Cesar I. optimized code for benchmark purpose. 08/03/01
;
;*****************************************************************************
;*****************************************************************************
;
;
;	IIR Biquad Structure
;
;                  d(n)         
;  x(n) ---> + -----.----- + --> y(n)
;           /|      |      |\
;          | |    [z-1]    | |
;          |        |        |
;          | |      v      | | 
;          | |--x-d(n-1)-x-| |         
;          |  -a1   |   b1   | 
;          |        |        |
;          |      [z-1]      |
;          |        |        |
;          |        v        |
;          |---x--d(n-2)--x--|
;            -a2         b2
;
;              "FB"   "FF"
;
;
;        "FB" = Feedback Terms
;        "FF" = Feedforward Terms
;
;
; Algorithm (for single biquad)
; -----------------------------
;  d(n) = x(n) - a1*d(n-1) - a2*d(n-2)
;  y(n) = d(n) + b1*d(n-1) + b2*d(n-2)
;
;
; Function Call
; -------------
;
;  short oflag = iircas4(DATA *x, DATA *h, DATA *r, DATA *dbuffer, ushort nbiq,
;                        ushort nx)
;
;   where:
; x[nx]: PASSED in XAR0.
;        Pointer to input vector of nx real elements.  
;        x(0) is the first input, 
;        while x(nx-1) is the last input.
;        
; h[4*nbiq]: PASSED in XAR1.
;        Pointer to filter coefficient vector with the following format:
;        H = a11 a21 b21 b11 ....a1i a2i b2i b1i
;         where i is the biquad index.
;         (i.e. a21: is the a2 coefficient of biquad 1). 
;         Pole (recursive) coefficients = a. 
;         Zero (non-recursive) coefficients = b
;
;        This array must be located in internal memory if it is 
;        accessed by the C55xx coefficient bus.
;
; r[nx]: PASSED in XAR2.
;        Pointer to output vector of nx real elements.  
;        In-place computation (r = x) is allowed.  r(0) is the first 
;        output, while r(nx-1) is the last output.
;
; dbuffer[2*nbiq + 2]: PASSED in XAR3.
;        Pointer to delay buffer of length 2*nbiq.  See figure below for  
;        organization. In the case of multiple-buffering schemes, this 
;        array should be initialized to 0 for the first filter block only. 
;        Between consecutive blocks, the delay buffer preserves the 
;        previous elements needed.
;
;        The first element in this array is special in that it 
;        contains the array index of the first buffer element in the 
;        delay buffer.  This is needed for multiple-buffering schemes, 
;        and should be initialized to zero (like all the other array 
;        entries) for the first  block only.
;
; nbiq:  PASSED in T0.
;        The number of biquads making up the filter.  
;
; nx:    PASSED in T1.
;        Number of elements in the input and output vectors
;
; oflag: RETURNED in T0.
;        Overflow error flag  (returned value)
;         = 1 if a 32-bit data overflow occurred in an intermediate 
;             or final result.
;         = 0 if no such overflow occurred.
;
;
; Memory and Pointer Use Definition
; ---------------------------------
;
;              "x[nx]"                  "r[nx]"
;      AR0(x)--> x(0)            AR2(r)-->r(0)     newest
;                x(1)                     r(1)
;                x(2)                     r(2)
;                 :                        :
;                 :                        :
;                x(nx-1)                  r(nx-1)  oldest
;
;
;      "dbuffer[2*nbiq+1]"            "h[4*nbiq]"
;                index            AR1(h)->a11
;      AR3(dn)-->d11                      b11 
;                d21                      a21
;                 :                       b21
;                dn1                      
; 				 dn2                      a12
;                                         b12
;                                         a22
;                                         b22
;                                          :
;                                         a1i
;                                         b1i
;                                         a2i
;                                         b2i
;
;      Def: dij / aij / bij  where i = delay #
;                                  j = biquad #

	.arms_off
	.cpl_off
	.mmregs
;	.align 0x100
	.noremark  5579
;******************************************
;*       Assigns
;******************************************
	.def	_iircas4
	.def    _c_int00

;******************************************
;*       Constant Defines
;******************************************
SCALE	.set	0

;******************************************
;*       Variable Declarations
;******************************************

;----------------------------------------------------------------
; Assign auxiliary registers for temporaries and address
; calculations.
;----------------------------------------------------------------
	.asg     CDP, db_ptr        ;circular pointer
 	.asg     AR0, in_ptr        ;linear pointer
 	.asg     AR1, h_ptr         ;circular pointer
 	.asg     AR2, out_ptr       ;linear pointer
    .asg     AR3, index         ;
	.asg     AR4, tap_updt      ;circular pointer

	
	.bss r,500      ;输入有多少个就留多少个
	.bss db, 6     ;中间变量 欲留
        
        .data
        
x: 		.word   -295   ,      406   ,     -137    ,     338   ,      292  ,       100  ,       459 ,        604    ,     259    ,     841
        .word   745  ,       641    ,    1004     ,    610  ,       927   ,      786 ,        761  ,       814 ,       1034    ,     710
        .word   712 ,       1129    ,     668    ,     791  ,       905  ,       865 ,        613 ,       1010 ,        826   ,      874
        .word  1174  ,       785    ,    1297    ,     960  ,       953   ,     1287 ,        680 ,       1350 ,        626  ,       740
        .word  978   ,      548     ,    930    ,     876   ,      920   ,     1007  ,       686 ,       1146  ,       808   ,      802
        .word   1053,         960   ,      793  ,       979  ,       749,         731 ,        809,         595 ,        946 ,        656
        .word  593  ,       914     ,    444    ,     555   ,      463   ,      384   ,      369 ,        236 ,        499  ,       149
        .word  315 ,        176    ,      83     ,   -116   ,       73  ,      -173  ,      -346 ,       -137 ,       -174  ,      -325
        .word   -329,        -186   ,     -408  ,      -321 ,       -460 ,       -414,        -568,        -579 ,      -570 ,       -535
        .word   -552 ,       -775   ,     -352  ,      -695 ,       -671  ,      -562 ,       -731,        -692 ,       -768,        -827
        .word  -933    ,    -942   ,     -962   ,     -984  ,      -949  ,     -1194 ,      -1092 ,      -1091  ,     -1513 ,      -1236
        .word  -1509  ,     -1427   ,    -1612  ,     -1357  ,     -1594 ,      -1858 ,      -1533 ,      -2142,       -1852 ,      -2112
        .word   -2300  ,     -2300 ,      -2532 ,      -2420 ,      -2662 ,      -2714 ,      -2724 ,      -2706 ,      -3042 ,      -2904
        .word   -2945 ,      -3171 ,      -3233 ,      -3252 ,      -3428 ,      -3615 ,      -3668 ,      -3802 ,      -4028 ,      -4150
        .word  -4235    ,   -4592  ,     -4429  ,     -4629  ,     -4920  ,     -4842  ,     -5159 ,      -5235  ,     -5309  ,     -5508
        .word   -5497 ,      -5502 ,      -5702 ,      -5685 ,      -5610 ,      -6023,       -5788,       -5975 ,      -6109 ,      -6022
        .word  -6236   ,    -6124  ,     -6299  ,     -6198  ,     -6279 ,      -6338 ,      -6383 ,      -6386 ,      -6371 ,      -6473
        .word  -6394   ,    -6544  ,     -6585  ,     -6439 ,      -6617 ,      -6582,       -6663 ,      -6556 ,      -6786,       -6852
        .word  -6800    ,   -6988  ,     -6929  ,     -7066  ,     -7024 ,      -7109 ,      -7266 ,      -7160  ,     -7312,       -7359
        .word   -7328  ,     -7556  ,     -7372 ,      -7499 ,      -7461 ,      -7480,       -7523,       -7496 ,      -7557 ,      -7503
        .word  -7465   ,    -7298  ,     -7344   ,    -7293  ,     -7187 ,      -7313 ,      -7288 ,      -7312 ,      -7382 ,      -7464
        .word  -7386   ,    -7492  ,     -7396  ,     -7276  ,     -7352 ,      -7354 ,      -7193 ,      -7283  ,     -7250 ,      -7178
        .word   -7164   ,    -7136 ,      -7149 ,      -7206 ,      -7117,       -7168 ,      -7201,       -7053 ,      -7073,       -7004
        .word  -6989   ,    -6985  ,     -6920 ,      -6952 ,      -6904 ,      -6867 ,      -6767,       -6841 ,      -6748 ,      -6613
        .word  -6721   ,    -6614  ,     -6638 ,      -6565 ,      -6579 ,      -6537 ,      -6503 ,      -6542 ,      -6526  ,     -6509