王爽 汇编语言 实验14这样做为什么不行呢？

Question

assume cs:code
data segment
db '00/00/00 00:00:00','$'
db 9,8,7,4,2,0
data ends

code segment
start:
mov ax,data
mov ds,ax
mov di,0
mov si,18

mov cx,6

s:
mov al,[si]
out 70h,al
in al,71h
mov ah,al
mov cl,4
shr ah,cl
and al,00001111b

add ah,30h
add al,30h

mov [di],ah
mov [di+1],al

inc si
add di,3
loop s

mov ax,data
mov ds,ax
mov si,0
mov ax,0b800h
mov es,ax
mov di,[160*12+30*2]

mov cx,17
cld
rep movsb

mov ax,4c00h
int 21h

code ends
end start