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; 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: Sending characters from keyboard to the STK600
;
;
; Input ports: None
;
; Output ports: on-board LEDs connected to PORTB.
;
;
; Subroutines: If applicable.
; Included files: m2560def.inc
;
; Other information:
;
; Changes in program: (Description and date)
;
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.include "m2560def.inc"
.def temp = r17
.def char = r16
.equ ubbrval = 12

.org 0x00
rjmp start

.org 0x30
setup:

ldi temp, 0xFF
out DDRB, temp		; Ports for output

ldi temp, 0x55
out PORTB, temp

ldi temp, ubbrval	; store prescaler value
sts UBRR1l, temp

ldi temp, (1<<TXEN1) | (1<<RXEN1)
sts UCSR1B, temp	; setting TX and RX flags enabled


start:
lds temp, UCSR1A	; read input
sbrs temp, RXC1 ; RXC1 = 1 => new character
rjmp start		; RXC1 = 0 => no character
lds char, UDR1	;Read character in UDR

output:
com char
out PORTB, char
com char

putChar:

lds temp, UCSR1A
sbrs temp, UDRE1	;UDRE1=1  == buffer empty
rjmp putChar		;UDRE1=0 ==buffer not empty
sts UDR1, char		;write character to UDR
rjmp start