953.asm

单片机开发资料光盘-双龙-686M.zip

.include"8535def.inc"
.org $000
 rjmp main
.org $006
 rjmp tim1_cmp
main: ldi r16,low(ramend)  ;初始化堆栈指针
      out spl,r16
      ldi r16,high(ramend)
      out sph,r16
      ldi r16,$c0          ;达比较匹配值时，OC1A变高
      out tccr1a,r16
      ldi r16,$0C          ;256分频，CTC=1，匹配时清定时器1
      out tccr1b,r16
      ldi r16,$20          ;PD5作输出
      out ddrd,r16
      clr r16              ;使TCNT1初值为0
      out tcnt1h,r16
      out tcnt1l,r16
      ldi r18,$01          ;送比较匹配值312
      out ocr1ah,r18
      ldi r18,$38
      out ocr1al,r18
      ldi r16,$10          ;允许定时器1比较匹配中断
      out timsk,r16
      clr r16              ;清中断标志
      out tifr,r16
      sei
here: rjmp here

tim1_cmp:
      in r1,sreg           ;保护标志          
      in r18,tccr1a        ;读TCCR1A
      sbrs r18,6           ;判COM1A0是否为1          
      rjmp  aa             
      ldi r18,$00          ; 若为1，送下次比较匹配值156
      out ocr1ah,r18
      ldi r18,156
      out ocr1al,r18
      ldi r18,$80          ;下次达到比较匹配值156时OC1A引脚变低
      out tccr1a,r18
bc:   out sreg,r1          ;恢复标志
      reti
aa:   ldi r18,$c0          ;若COM1A0为零，下次达到比较匹配值时OC1A引脚变高
      out tccr1a,r18    
      ldi r18,$01          ;送下次比较匹配值312            
      out ocr1ah,r18
      ldi r18,$38
      out ocr1al,r18
      rjmp bc