Blink LEDs according to Switch state on AVR8/atmega2560 - GCC version

Prac2-gcc.asm

; Created: 25/11/2019 9:45:37 AM
; Author : Annon

; defining some labels to make the code easier to read
LEDs = 20
Switches = 21
outer = 22
inner = 23
inner1 = 24

; GPIO registers (according to datasheet)
DDRA = 0x1
PORTA = 0x2
PINC = 0x6
DDRC = 0x7
PORTC = 0x8

.text
.section	.rodata
.string "Look ma, I'm on a chip!!" ; :P

.text
.org 0000 ; start the code at 0x0000 - we arent using interrupts so don't waste space on them
.global Start
Start:
  clr r19
  OUT DDRC, r19
  ser r19
  OUT DDRA, r19
  OUT PORTC, r19
  
Loop:
  in Switches,PINC ; read switches
  com Switches ; invert
  cbr Switches, 0x7F ; mask out the lower 7 bits
  cpi r21, 0x80 ; compare r21 with 0x80
  breq setLeds ; turn on leds
  brne clrLeds ; make sure the leds turn off if not set
  
setLeds:
  ser LEDs ; set all bits high
  out PORTA, LEDs ; send them to the leds
  rcall wait ; wait ~1s
  clr LEDs ; set all bits low
  out PORTA, LEDs ; send them to the leds
  rcall wait ; wait ~1s
  rjmp Loop ; jump back to main loop
  
clrLeds:
  clr LEDs ; set all bits low
  out PORTA, LEDs ; send them to the leds
  rjmp Loop ; jump back to main loop
  
wait: ; 255 * 252 * 83 * 3 = 16000740/16mhz = 1.0004625s
  ldi outer,0
waitouter:
  rcall waitinner
  dec outer
  brne waitouter
  ret
waitinner:
  ldi inner,253
waitinner1:
  rcall waitininner
  dec inner
  brne waitinner1
  ret
waitininner:
  ldi inner1,84
waitininner1:
  dec inner1
  brne waitininner1
  ret