写了如下两个程序，目的都是为点亮某一8字lcd的管脚。
lcd管脚用pa口的1,3脚和pc口的6脚输出。

现在的问题是程序a用循环的做的通过了，程序b用定时器0做的死活不肯点亮。

请达人指点~

已知：lcd要信号翻转轮流输入两极才能点亮。因为我用的不是lcd模块，所以直接
接在单片机引脚上。

程序a:                                                                
.include"8515def.inc"                        
.def temp=r20
.def temp1=r21
.org $0000
rjmp lcd
.org $0010 
lcd:  ldi r16,high(ramend)
      out sph,r16
      ldi r16,low(ramend)
      out spl,r16
      ldi r16,$19 
      ser r17
      out ddra,r17
      out ddrc,r17
      ldi temp,$0a
      out ddra,temp
      ldi temp,$40
      out ddrc,temp      
lp:   ldi temp,$00
      out porta,temp
      ldi temp1,$40
      out portc,temp1
      rcall delay
      ldi temp,$0a
      out porta,temp
      ldi temp1,$00
      out portc,temp1
      rcall delay
      rjmp lp
delay:  push r16
     l0:push r16
     l1:push r16
     l2:push r16
     l3:dec r16
        brne l3
        pop r16
        dec r16
        brne l2
        pop r16
        dec r16
        brne l1
        pop r16
        dec r16
        brne l0
        pop r16
        ret   

程序b:
.include"8515def.inc"
.def temp=r20                                  
.def temp1=r21                                
.def temp2=r22                               
.def temp3=r23
.def temp4=r24
.def temp5=r25
.org $000
rjmp reset
.org $007
rjmp intt0
intt0: cpi temp4,$ff
       brne a
       out porta,temp
       out portc,temp2
       clr temp4
       rjmp b
a:     out porta,temp2
       out portc,temp1
       ser temp4
b:     out tcnt0,temp3
       reti
.org $010
reset: 
       ldi temp,$0a
       out ddra,temp
       ldi temp1,$40
       out ddrc,temp1
       ldi temp2,$00
       out porta,temp2 
       out portc,temp1
       ser temp4
       ldi temp3,128
       out tcnt0,temp3
       ldi temp5,$05
       out tccr0,temp5
       ldi temp5,$02
       out timsk,temp5
       sei
c:     rjmp c