;Dragon12 Plus Assembly Language Shell Program for CodeWarrior IDE
;In Dragon12+ RAM address is from $1000-3FFF 
;We use RAM addresses starting at $1000 for scratch pad (variables) and $3FFF for Stack 
;To Assemble and Single Step. In Full Chip Simulation mode, Press F7 (to Make),then F5 to Debug (True-Time Simulation & Real Time Debugger)
;In True-Time Simulation & Real Time Debugger press F11 to single step

;To Download and Execute, Make sure you are in HCS12 Serial Monitor Mode before downloading 
;and also make sure SW7=LOAD (SW7 is 2-bit red DIP Switch on bottom right side of the board and must be 00, or LOAD) 
;Press F7 (to Make), then F5(Debug) to downLOAD,and F5 once more to start the program execution

;SEE THE PORTB TOGGLE PROGRAM FOR DRAGON12+ ON THIS WEBSITE AS AN EXAMPLE OF HOW WE USE THIS SHELL 

    
        ABSENTRY Entry        ; for absolute assembly: mark this as application entry point
        
    
; Include derivative-specific definitions 
		INCLUDE 'mc9s12dp256.inc'     ;CPU used by Dragon12+ board
 
 
;----------------------USE $1000-$2FFF for Scratch Pad 
R1      EQU     $1001
R2      EQU     $1002
R3      EQU     $1003

;code section
        ORG   $4000     ;Flash ROM address for Dragon12+
Entry:
	LDS     #$4000    ;Stack
        LDAA    #$FF
        STAA    DDRB		;Make PORTB output
  ;PTJ1 controls the LEDs connected to PORTB (For Dragon12+ ONLY)
        LDAA    #$FF      	
	STAA    DDRJ   	;Make PORTJ output, (Needed by Dragon12+) 
	LDAA    #$0
	STAA    PTJ   	;Turn off PTJ1 to allow the LEDs on PORTB to show data (Needed by Dragon12+) 
;
;-------Put your code here
        NOP         ;put your code here
      




  
;-----------------
  
;----------DELAY
DELAY

        PSHA		;Save Reg A on Stack
        LDAA    #10		;Change this value to see  
        STAA    R3		;how fast LEDs Toggle
;--10 msec delay. The Serial Monitor works at speed of 48MHz with XTAL=8MHz on Dragon12+ board
;Freq. for Instruction Clock Cycle is 24MHz (1/2 of 48Mhz). 
;(1/24MHz) x 10 Clk x240x100=10 msec. Overheads are excluded in this calculation.         
L3      LDAA    #100
        STAA    R2
L2      LDAA    #240
        STAA    R1
L1      NOP         ;1 Intruction Clk Cycle
        NOP         ;1
        NOP         ;1
        DEC     R1  ;4
        BNE     L1  ;3
        DEC     R2  ;Total Instr.Clk=10
        BNE     L2
        DEC     R3
        BNE     L3
;--------------        
        PULA			;Restore Reg A
        RTS
;-------------------

            
;**************************************************************
;*                 Interrupt Vectors                          *
;**************************************************************
       ORG   $FFFE
       DC.W  Entry     ;Reset Vector. CPU wakes here and it is sent to start of the code at $4000