;ledlight.asm
;A beginner's program
;lights up an LED on pin PORTB0
;LED is arranged to sink current into the PORTB0 pin
;assembled using Atmel's avrasm assembler.


;the following .inc file should be placed in the same directory as
;this assembly program

.include "1200def.inc"

.cseg
.org 0
         rjmp    RESET           ;Reset Handle
         rjmp    RESET
         rjmp    RESET

RESET:   ldi r16, 0b11111111     ;load register r16 with all 1's
         out DDRB, r16           ;configure PORT B for all outputs

loopit:  ldi r16, 0              ;load register r16 with all 0's
         out PORTB, r16          ;output the contents of r16
                                 ;on PORTB
                                 ;Thus PORTB0 pin is at logic '0'
                                 ;as well as all the other PORTB
                                 ;pins. This enables the current
                                 ;through the LED to flow into
                                 ;PORTB0 pin and the LED lights up
         rjmp loopit