iir_c55x.asm

用dsp解压mp3程序的算法

	.def _iir_c55x
_iir_c55x
    pshm  ST1_55               ; save ST1, ST2, and ST3
    pshm  ST2_55
    pshm  ST3_55
   
    or    #0x340,mmap(ST1_55)  ; set FRCT,SXMD,SATD
    bset  SMUL
    bset  SATA
 
    mov   *AR0<<16,AC0         ; get the value of 'out'  
    masm  *AR2+,*AR3+,AC0      ; out-= DEN[j][1] * delay[1+(j*section)]
    masm  *AR2,*AR3-,AC0       ; out-DEN[j][2]*delay[2+(j*section)]
    mov   *AR3-,T0             ; save the value of delay[1+(j*section)]
    mov   rnd(hi(AC0)),*AR3    ; delay[j*section]=out-DEN[j][2]*delay[2+(j*section)]
    mov   *AR3+,T1             ; save the value of delay[(j*section)] 
    mov   AC0,AC1              
    mov   #0,AC0
    macm  *AR1+,*AR3+,AC0      ; delay[1+(j*section)]*NUM[j][1]
    add   AC1,AC0              ; out=delay[(j*section)] + delay[1+(j*section)]*NUM[j][1]
    macm  *AR1,*AR3,AC0        ; out=out+delay[2+(j*section)]*NUM[j][2]
    mov   T0,*AR3-             ; delay[2+(j*section)]=delay[1+(j*section)]
    mov   T1,*AR3              ; delay[1+(j*section)]=delay[(j*section)]
    mov   rnd(hi(AC0)),*AR0    ; save the value of 'out'
    
    BCLR  FRCT
    BCLR  SATD
    BCLR  SXMD
    BCLR  SATA
    BCLR  SMUL
    popm  ST3_55               ; restore ST1, ST2, and ST3
    popm  ST2_55
    popm  ST1_55
    ret
	
   .end