light.txt

利用8255输入8位开关信号

pa8255  equ 300h
pb8255  equ 301h
pc8255  equ 302h
ctr8255 equ 303h
dseg segment
command db 10010000b;特征位1,A组方式0,A口输入,PC4-7暂未用,B组方式0,B口输出,PC0-3暂未用
dseg ends
cseg segment
     assume cs:cseg,ds:dseg
start: mov ax,dseg
       mov ds,ax
       mov dx,ctr8255
       mov al,command
       out dx,al
ag:    mov dx,pa8255
       in  al,dx
       mov dx,pb8255
       xor al,0ffh
       out dx,al
       mov ah,0bh
       int 21h
       and al,al
       jz  ag
       mov ah,8
       int 21h
       cmp al,27
       jnz ag
       mov ax,4c00h
       int 21h
cseg   ends
       end start
pa输入开关信号，屏幕输出
pa8255  equ 300h
pb8255  equ 301h
pc8255  equ 302h
ctr8255 equ 303h
dseg segment
command db 10010000b
dseg ends
cseg segment
     assume cs:cseg,ds:dseg
start: mov ax,dseg
       mov ds,ax
       mov dx,ctr8255
       mov al,command
       out dx,al
ag:    mov dx,pa8255
       in  al,dx

       mov bl,al
       mov bh,al

       mov cl,4
       shr bl,cl
       call disp
       
       mov  bl,bh
       call disp

       mov dl,13
       mov ah,2
       int 21h

       mov ah,0bh
       int 21h
       and al,al
       jz  ag

       mov ah,8
       int 21h
       cmp al,27;按esc键结束
       jnz ag
       mov ax,4c00h
       int 21h

disp   proc near
       and bl,0fh
       mov dl,bl
       or  dl,30h
       cmp dl,3ah
       jc  next
       add dl,7
next:  mov ah,2
       int 21h
       ret
disp   endp
cseg   ends
       end start