.include "8535def.inc"
.org $000
 rjmp main
.org $009
 rjmp tim0_ovf
main:  ldi r16,low(ramend) ;棧指針置初值
        out spl,r16
        ldi r16,high(ramend)
        out spH,r16
        ldi r16,$01        ;允許T0溢出中斷
        out timsk,r16
        ldi r16,$05        ;1024分頻
        out tccr0,r16
        ldi r17,131        ;T/C0置初值131
        out tcnt0,r17
        out tifr,r16
        ldi r16,$ff        ;PC口作輸出
        out ddrc,r16
        sei
here:   rjmp here

tim0_ovf:in r1,sreg        ;保存sreg
         ldi r17,13
         out tccr0,r17
         in r18,portc      ;讀C口數據寄存器
         com r18           ;取反
         out portc,r18     ;送C口數據寄存器
         out sreg,r1       ;恢復sreg
         reti