; Program to use the timer overflow interrupt

prog:    equ     $0800
data:    equ     $0900
int_vec: equ     $0B10

TSCR:    equ     $0086
TMSK2:   equ     $008D
TFLG2:   equ     $008F

DDRA:    equ     $0002
PORTA:   equ     $0000


CODE:    section .text      ;The stuff which follows is program code
         org     prog       ;set program counter to 0x0800
         lds     #$0A00     ;set the stack pointer
         ldaa    #$FF
         staa    DDRA       ; Port A output
         clr     PORTA      ; 0 -> Port A
         ldaa    #$80
         staa    TSCR       ; Turn on timer
         ldaa    #$80
         staa    TMSK2      ; Enable timer overflow interrupt
         ldaa    #$80
         staa    TFLG2      ; Clear TOI flag
         cli                ; Enable interrupts
loop:    bra     loop       ; Wait forever

toi_isr: inc     PORTA      ; 
         ldaa    #$80
         staa    TFLG2      ; Clear TOI flag
         rti

VEC:     section .text      ; Constant vectors
         org     int_vec
         dc.w    0          ; BDLC
         dc.w    0          ; ATD             
         dc.w    0          ; reserved
         dc.w    0          ; SCI0          
         dc.w    0          ; SPI             
         dc.w    0          ; Pulse acc input 
         dc.w    0          ; Pulse acc overflow 
         dc.w    toi_isr    ; Timer overflow  
         dc.w    0          ; Timer channel 7 
         dc.w    0          ; Timer channel 6 
         dc.w    0          ; Timer channel 5 
         dc.w    0          ; Timer channel 4 
         dc.w    0          ; Timer channel 3 
         dc.w    0          ; Timer channel 2 
         dc.w    0          ; Timer channel 1 
         dc.w    0          ; Timer channel 0 
         dc.w    0          ; Real time       
         dc.w    0          ; IRQ             
         dc.w    0          ; XIRQ            
         dc.w    0          ; SWI             
         dc.w    0          ; illegal         
         dc.w    0          ; cop fail        
         dc.w    0          ; cop clock fail  
         dc.w    $ff80      ; RESET