fir.asm

有限冲击响应滤波器

    .mmregs

   .asg    0, ret_addr
   .asg    3, h
   .asg    4, r
   .asg    5, NX
   .asg    6, nc
   
   .asg ar5, arg_x
   .asg ar3, arg_h
   .asg ar4, arg_r
      
   .def    _fir
   .global _fir

   .text

_fir

        PSHM    ST0                 ; 1 cycle
        PSHM    ST1                 ; 1 cycle
        RSBX    OVA                 ; 1 cycle
        RSBX    OVB                 ; 1 cycle

        SSBX	SXM                 ; 1 cycle
        SSBX    FRCT                ; 1 cycle
        STLM    A,     arg_x        ; 1 cycle   AR2,
        MVDK   *sp(h), arg_h        ; 1 cycles  AR3,
        MVDK   *sp(r), arg_r        ; 1 cycles  AR5,
        LD     *sp(NX), A           ; 1 cycle
        SUB	    #3, A				; 2 cycles
     	STL	    A, *sp(nc)			; 1 cycle                          
        MPY	  *arg_h+,*arg_x+,  A
        RPT   *sp(nc)
        MAC   *arg_h+,*arg_x+,  A
        MACR  *arg_h+,*arg_x+,  A 
        STH   A, 1, *arg_r 
        POPM    ST1                  ; 1 cycle
        POPM    ST0 
        nop
        nop                           ; 1 cycle
        ret