exp3.asm

微机接口芯片8255 8254 ADC0809的实验

data segment 
     ioport  equ 0c400h-0280h
     ioport0     equ ioport+298h
data ends
code segment 
     assume  cs:code,ds:data
start:mov ax,data 
      mov ds,ax                    ;段装填
on:   mov dx,ioport0               ;启动转换
      out dx,al                    
delay:push cx                      ;延时
      push ax
      mov cx,100h
   T1:mov ax,100h
   T2:dec ax
      jnz T2
      loop T1
      pop ax 
      pop cx
      in al,dx                     ;读取转换结果放在AL中
      mov bl,al
      mov cl,4
      shr al,cl
      call disp                    ;显示高4位
      mov al,bl
      and al,0fh
      call disp                    ;显示低4位
      mov dl,0ffh
      mov ah,6
      int 21h
      jz on                        ;没有键按下则循环
exit: mov ah,4ch
      int 21h                      ;返回DOS
disp proc                          ;disp子程序
     mov dl,al
     cmp dl,9
     ja  test1
     add dl,30h                    ;小于等于9加30h
     jmp ttt
test1:add dl,37h                   ;大于9加37h
ttt:  mov ah,2
      int 21h
      ret
disp endp
  code ends
      end start