;
;   adaptive.asm - Adaptive filter for system identification 
;                                  
;   Prototype: unsigned int adaptive(int *in, int *d, int *x, int *w,
;		   unsigned int Ns, unsigned int N, unsigned int index)
;
;   Entry: in[] - input signals
;          d[] - reference signal
;          x[] - adaptive filter delay-line buffer
;          w[] - adaptive filter coefficient array
;          Ns  - number of samples per block
;          N   - order of the adaptive filter
;          index - index to x[]
;
;   Return: T0 = Adaptive filter delay-line buffer index         
;

TWOMU .set 0x1000      ; 2*MU

    .def  _adaptive
    .sect "lms_code"
	
_adaptive:                       
    pshm ST1_55              ; Save ST1, ST2, and ST3
    pshm ST2_55
    pshm ST3_55
	
    mov  mmap(AR3),BSA45
    mov  mmap(T1),BK47  
    mov  mmap(AR2),BSA23
    mov  mmap(T1),BK03
    mov  AR4,AR3            ; AR3 -> x[] as circular buffer
    mov  #0,AR4             ; AR4 -> w[] as circular buffer 
			
    or   #0x340,mmap(ST1_55); Set FRCT,SXMD,SATD
    or   #0x18,mmap(ST2_55) ; Enable circular addressing mode
    bset SATA               ; Set SATA

    sub  #1,T0
    mov  mmap(T0),BRC0      ; Set Sample block loop counter  
    sub  #2,T1
    mov  mmap(T1),BRC1      ; Counter for LMS update loop 
    mov  mmap(T1),CSR       ; Counter for FIR filter loop		
    rptblocal loop-1        ; for (n=0; n<Ns; n++)
    mov  *AR0+,*AR3         ; x[n]=in[n]
    mpym *AR3+,*AR4+,AC0    ; temp = w[0]*d[0] 
||  rpt  CSR                ; for (i=0; i<N-1; i++)
    macm *AR3+,*AR4+,AC0    ;   y += w[i]*x[i]
    sub  *AR1+ <<#16,AC0    ; AC0=-e=y-d[n], AR1 points to d[n]
    mpyk #-TWOMU,AC0
    mov  rnd(hi(AC0)),mmap(T1); T1=2*mu*e[n]
    rptblocal lms_loop-1    ; for(j=0; i<N-2; i++)
    mpym *AR3+,T1,AC0       ;   AC0=2*mu*e*x[i]     
    add  *AR4<<#16,AC0      ;   w[i]+=2*mu*e*x[i]     
    mov  rnd(hi(AC0)),*AR4+
lms_loop 
    mpym *AR3,T1,AC0        ; w[N-1]+=2*mu*e*x[N-1]
    add  *AR4<<#16,AC0    
    mov  rnd(hi(AC0)),*AR4+ ; Store the last w[N-1]  
loop                              

    popm ST3_55             ; Restore ST1, ST2, and ST2
    popm ST2_55
    popm ST1_55	
    mov  AR3,T0             ; Return T0=index
||  ret
	
    .end