; Test 4: Board kennenlernen, Timer im Interupt mode

.NOLIST
.INCLUDE "m8515def.inc"
.LIST


RESET: 
ldi r16,high(RAMEND); Main program start
out SPH,r16 ; Set Stack Pointer to top of RAM
ldi r16,low(RAMEND)
out SPL,r16
sei ; Enable interrupts


init_Ex1:
	ldi r16,(1<<CS02)|(1<<CS00)
	out TCCR0,r16 ; Timer clock = system clock / 1024
	ldi r16,1<<TOV0
	out TIFR,r16 ; Clear TOV0/ clear pending interrupts
	ldi r16,1<<TOIE0
	out TIMSK,r16 ; Enable Timer/Counter0 Overflow Interrupt
	ser r16
	out DDRB,r16 ; Set Port B as output


loop: ; label
	in r16,TIFR ; load TIFR in register 16
	sbrs r16,TOV0 ; skip next instruction if bit (zero) in register
	; (r16) is set
rjmp loop ; jump to loop if no Timer0 overflow occurred
; Event Service Code starts here

;--------------------------------------------------

ISR_TOV0:
	push r16
	in r16,SREG
	push r16
	in r16,PORTB ; Read Port B
	com r16 ; Invert bits of r16 register
	out PORTB,r16 ; Write Port B
	pop r16
	out SREG,r16
	pop r16
reti

ret