; #########################################################################################
; # Indiana University                                                                    #
; # Computer Science Department                                                           #
; #                                                                                       #
; # Example Program 2                                                                     #
; #                                                                                       #
; # DESCRIPTION:                                                                          #
; #                                                                                       #
; # This program defines 4 storage bytes in memory and adds the values contained in       #
; # the locations. The sum is placed in a long word variable called result.               #
; #                                                                                       # 
; # AUTHOR:                                                                               #
; # Bryce Himebaugh (bhimebau@cs.indiana.edu)                                             #
; # IUCS Staff                                                                            #
; # 6/21/99                                                                               #
; #                                                                                       #
; #########################################################################################


	SECTION code
START:  	
        clr.l d0                           ; initialize register to hold a data byte. 
        moveq.l #4,d1                      ; intialize the loop counter stored in d0
        clr.l d2                           ; initialize register used to hold the sum
        lea byte_array,a0                  ; load the address if byte_array into a0
add_loop:
        move.b (a0)+,d0                    ; move one byte @ a0 to d0, inc. a0
        add.l d0,d2                        ; add the d0 to d2  
        subq.l #1,d1                       ; decrement the loop counter
        bne add_loop                       ; branch back if the loop counter is not 0
        move.l d2,result                   ; move the register containing the sum to memory

        trap #15                           ; terminate using TRAP #15 mode 0 (d1=0).    

        SECTION data                       ; variables need to go in data section for 
                                           ; watch window visability through the debugger
byte_array:
        ds.b 4                             ; reserve 4 bytes at location byte_array
result:
        ds.l 1                             ; reserve 1 long word at location result