Read a switch and flash some LEDs - AVR8/atmega2560

Prac2.asm

; Created: 25/11/2019 9:45:37 AM
; Author : Annon
; defining some labels to make the code easier to read
.def LEDs = r20
.def Switches = r21
.def outer = r22 .def inner = r23
.def inner1 = r24
.org 0000 ; start the code at 0x0000 - we arent using interrupts so don't waste space on them
.db "Look ma, I'm on a chip!!" ; :P
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, $7F ; mask out the lower 7 bits
  cpi r21, $80 ; 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