;>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
; 1DT301, Computer Technology I
; Date: 2017-09-289
; Author:
; Christian Fagerholm
; Amelie Löwe
;
; Lab number: 4
; Title: How to use the PORTs. Digital input/output. Subroutine call.
;
; Hardware: STK600, CPU ATmega2560
;
; Function: Describe the function of the program, so that you can understand it,
; even if you're viewing this in a year from now!
;
; Input ports: None
;
; Output ports: example on-board LEDsonnected to PORTB.
;
;
; Subroutines: If applicable.
; Included files: m2560def.inc
;
; Other information:
;
; Changes in program: (Description and date)
;
;<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<


; Replace with your application code
.org 0x00
rjmp setup
.org OVF1addr
rjmp timer1_int


.org 0x72
setup:
.equ timer_start = 65036
.def temp = r16
.include "m2560def.inc"
    ldi r20, HIGH(RAMEND)       ;Initiating Stack
    out SPH, r20                ;
    ldi r20, LOW(RAMEND)
    out SPL, r20

	ldi r19, 0x00

    ldi r17, 0xFF  ;Outputs, Port B
    out DDRB, r17

	ldi temp, 0x05	; prescaler value 1024
	sts TCCR1B, temp

	ldi temp, (1<<TOIE1) ; Timer 1 enable flag, TOIE1
	sts TIMSK1, temp ; to register TIMSK

	ldi temp , HIGH(timer_start)
	sts TCNT1H, temp
	ldi temp, LOW(timer_start)
	sts TCNT1L, temp


	sei ; enable global interrupt


start:
	nop
    rjmp start


timer1_int:
push temp ; timer interrupt routine
in temp, SREG ; save SREG on stack
push temp

ldi temp, HIGH(timer_start)
sts TCNT1H, temp
ldi temp, LOW(timer_start)
sts TCNT1L, temp

com r19
out PORTB, r19

pop temp ; restore SREG
out SREG, temp
pop temp ; restore register

reti