.include "m328pdef.inc"

; Define constants
#define F_CPU 16000000  ; CPU clock frequency (16 MHz)

; I / O Register Definitions
.equ LED_DDR = DDRB
               .equ LED_PORT = PORTB
                               .equ LED_PIN = PB5

                                   ; Main program
RESET:
ldi r16, 1 << LED_PIN    ; Set LED pin as output
out LED_DDR, r16

MAIN:
ldi r16, 1 << LED_PIN    ; Load value to toggle the LED
out LED_PORT, r16      ; Turn on the LED
_delay_ms(1000)        ; Delay for 1 second
cbi LED_PORT, LED_PIN  ; Turn off the LED
_delay_ms(1000)        ; Delay for 1 second
rjmp MAIN              ; Repeat

; Delay subroutine
_delay_ms:
; Input: r24 = number of milliseconds
               ; Output: None
ldi r17, 100  ; Load constant
DELAY_LOOP:
dec r24        ; Decrement milliseconds
brne DELAY_LOOP  ; Repeat if not zero
ret

; End of program