;Displaying Overflow Timer on LEDs of PORTB in Assembly for Dragon12+ Trainer with Codewarrior
;Modified from Example 9-3 in HCS12 book by Mazidi & Causey

        ABSENTRY Entry        ; for absolute assembly: mark this as application entry point
    
; Include derivative-specific definitions 
		INCLUDE 'mc9s12dp256.inc'     ;CPU used by Dragon12+ board
 
 

;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+) 
;
;-------Toggling ALL LEDs connected to PORTB
   			
	      LDAA 	#$80			
	      STAA	TSCR1			
	      LDAA 	#$04	    ;Prescaler=16 (Try 0-7 values to see changes on LEDs) 
	      STAA	TSCR2			
	      LDAA	#0			
OVER	  BSET	TFLG2,%10000000	      ;clear the Timer overflow flag (writing HIGH clears it)
H1	    BRCLR	TFLG2,mTFLG2_TOF,H1   ;wait for Timer Overflow
	      INCA				                ;keep adding the overflows
	      STAA	PORTB                 ;and dump it on PORTB to see
	      BRA	OVER

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