comment            ;
1、从cmos中取出一个
2、转换成十进制，放入临时存储段
3、循环6次
4、一次显示所有  
;   
可以动态显示时钟的                  
              assume    cs:code
        code  segment
      start:
;设置源地址和目的地址      
              mov       ax,cs
              mov       ds,ax
              mov       si,offset begin         ;源地址
              mov       ax,0
              mov       es,ax
              mov       di,200h     ;目的地址
              mov       cx,offset over-offset begin
              cld
              rep       movsw
;修改中断向量表
              mov       ax,0
              mov       ds,ax
              mov       bx,1ch*4
              mov       ax,200h
              mov       [bx],ax
              mov       ax,0
              mov       [bx+2],ax
;退出
              mov       ax,4c00h
              int       21h
      begin:
              push      ax
              push      bx
              push      cx
              push      ds
              push      si
              push      es
              push      di
              push      bp          ;保护现场
              
              jmp       ok
        data  segment
              db        9,8,7,4,2,0 ;单元地址
       temp:  dw        8 dup(0)
        data  ends
         ok:
              mov       ax,data
              mov       ds,ax
              mov       si,0
              lea       bx,temp
              mov       bp,0
              mov       cx,6
;从端口里取数据，转换后放入temp里              
          s:
              mov       al,[si]
              out       70h,al
              in        al,71h
              mov       ah,al
              
              and       ah,00001111b
              push      cx
              mov       cl,4
              shr       al,cl
              pop       cx
              
              mov       [bx],ax
              cmp       bp,2
              jb        g           ;/
              ja        d           ;:
              mov       al,-10h
              jmp       c
          g:  mov       al,'/'-30h
              jmp       c
          d:  mov       al,':'-30h
              jmp       c
          c:
              mov       [bx+2],al
              inc       si
              inc       bp
              add       bx,3
              loop      s
              mov       ax,'$'      ;结束标志
              mov       [bx],ax
              
;从temp里取出数据显示，遇到$结束             
              lea       bx,temp
              mov       ax,0b800h
              mov       es,ax
              mov       di,120
         s0:
              mov       al,[bx]
              cmp       al,'$'
              je        return
              add       al,30h
              mov       es:[di],al
              mov       al,2
              mov       es:[di+1],al
              inc       bx
              add       di,2
              loop      s0
     return:
              mov       al,20h
              mov       es:[di-2],al
              pop       bp
              pop       di          ;恢复现场
              pop       es
              pop       si
              pop       ds
              pop       cx
              pop       bx
              pop       ax
              iret
       over:  nop
        code  ends
              end       start