; Module definition for external referance
        	.def	FIRFILTC_CALC	
order		.set	71
FIRFILTC_CALC:		
    		POPD	*+ 				; Store the Return Address in stack
			SAR		AR0,*+     		; Store the Caller's Frame Pointer
			SAR		AR1,* 
									;create the software stack
			LAR		AR2,*+,AR2		; ARP=AR2, AR2=FP, AR1=FP+1  
		    SETC	SXM		    
		    SETC    OVM
		    SPM		#0
									;initialize 
		    SBRK	#3				; ARP=AR2, AR2->#fir
		    LAR		AR2,*           ; ARP=AR2, AR2= FIRFILT_handle->*coeff_ptr
			LAR		AR3,*+		;ARP=AR2, AR2->brindex & AR3=coeff_ptr->coeff[N]=H(N)
	    	LAR		AR0,*+			; ARP=AR2, AR2->order & AR0=brindex 
									;at this time AR2->order,AR0=brindex,AR3=H[N]
		    MAR		*+              ; ARP=AR2, AR2->dbuffer_ptr
		    LAR 	AR4,*,AR4		; ARP=AR4, AR4->dbuffer_ptr, AR2->dbuffer_ptr
		    						; AR4=dbuffer_ptr pointing to the oldest sample
		    LACL	#0				; Clear ACC
		    LT		*BR0-,AR2		; ARP=AR2, AR2->dbuffer_ptr  
									;at this time AR4 ->next position confine
									;by bit reversion
		    SAR		AR4,*+,AR3	; ARP=AR3, AR2->input 
								;update the dbuffer_ptr for the next calcuate
								;at this time AR3->H[N],AR4->X[1],TREG=X[0]
		    .loop order-1		    
		    MPY		*-,AR4          ; ARP=AR5  
			LTA		*BR0-,AR3       ; ARP=AR3        
            .endloop 
		    MPY		*-,AR2			; ARP=AR2, AR2->output
	        LTA		*+,AR3 			; ARP=AR3,TREG=input, AR2->output,AR3->H[0]
	        MPY		*,AR2			; ARP=AR2, AR2->output,PREG=H[0]*input data
            APAC					; store the last PREG
;-----------------------------------;below is left shift one bit 
            SACH	*				; 32 bit of ACC is added with itself to get Q31 result
            ADDH	*				
            SACL	*
            ADDS	*				; ARP=AR2, AR2->output
;-----------------------------------below is store output to fir.output
            ADD		#1,15			; Round the result
            SACH	*-				; ARP=AR2, AR2->input
;-----------------------------------below`is store the newest sample to the
									;last position of buffer window
            LACL	*,AR4			
            SACL	*,0,AR1
;-----------------------------------below is pop the software stack
			CLRC	OVM
			SBRK	#2
			LAR		AR0,*-          ; Retrive Caller's frame pointer
								    ;also conventional for test program
			PSHD	*               ; Push the return address to TOS
			RET                     ; Return to the caller