实验14out 70h in 71h 无输出？

n2zee

assume cs:code,ds:data
data segment
db 9,8,7,4,2,0
db '/','/',' ',':',':'
data ends
code segment
start:
mov ax,data
mov ds,ax
mov si,0
mov bx,0b800h
mov es,bx
mov di,160*12+40*2
mov cx,5
s:
push cx
mov al,[si]
out 70h,al
in al,71h

mov ah,al
mov cl,4
shr ah,cl
and al,00001111b
add al,30h
add ah,30h
mov byte ptr es:[di],ah
mov byte ptr es:[di+2],al
mov ah,byte ptr [si+6]
mov byte ptr es:[di+4],ah
add di,6
inc si
pop cx
loop s
mov ax,4c00h
int 21h
code ends
end start
我的机器，用out 70h,al in al,71h 无输出，al总是0，谁知到怎么回事？