汇编程序49：实验14 访问CMOS RAM(显示系统时间)

 assume cs:code
 ;安装程序,使用指令out和in指令
 code segment
     start:
           mov ax,cs
           mov ds,ax
           mov si,offset sub1
           mov ax,0020h
           mov es,ax
           mov di,
           mov cx,offset sub2 - offset sub1
           cld
           rep movsb ;复制程序

           mov ax,
           mov es,ax
           mov word ptr es:[7ch*],200h
           mov word ptr es:[7ch*+],
           mov ax,4c00h
           int 21h ;入口地址附加
      sub1:
           out 70h,al ;向端口70h写入字节数据al
           in al,71h  ;向端口71h读入字节数据al

           mov ah,al
           mov cl,
           shr ah,cl ;高位BCD码
           and al,00001111b ;低位BCD码

           add ah,30h
           add al,30h ;转化为ASCLL码

           mov bx,0b800h
           mov es,bx
           mov byte ptr es:[*+*+di],ah
           mov byte ptr es:[*+*+di],al ;向显示屏写入数据

           add di, ;每次偏移+
           iret
      sub2:
           nop
 code ends

 end start

 assume cs:code
 ;测试程序
 code segment
     start:
           mov di,
           mov al,
           int 7ch
           mov byte ptr es:[*+*+di],'/'
           add di,
           mov al,
           int 7ch
           mov byte ptr es:[*+*+di],'/'
           add di,
           mov al,
           int 7ch
           mov byte ptr es:[*+*+di],' '
           add di,
           mov al,
           int 7ch
           mov byte ptr es:[*+*+di],':'
           add di,
           mov al,
           int 7ch
           mov byte ptr es:[*+*+di],':'
           add di,
           mov al,
           int 7ch
           mov ax,4c00h
           int 21h
 code ends

 end start