4-1.asm

TCP_USB试验平台下的几个常见的实验的相应要求与代码

data segment
  PA equ 288h
  PB equ 289h
  PC equ 28ah
  CTL55 equ 28bh
  TABLE db 3fh,06h,5bh,4fh,66h,6dh,7dh,07h,7fh,6fh,77h,7fh,39h,3fh,79h,71h
data ends
code segment
  assume ds:data,cs:code
start:
  mov ax,data
  mov ds,ax 
  mov cx,10h
  mov dx,CTL55
  mov al,10011000b
  out dx,al 
L0:
  mov dx,PC
  in al,dx
  test al,80h
  jnz L0
  mov dx,PA
  in al,dx
  and al,0fh
  lea bx,TABLE
  xlat
  mov dx,PB
  out dx,al
L1:
  mov dx,PC
  in al,dx
  test al,80h
  jz L1  
  loop L0
  mov ah,4ch
  int 21h
code ends 
    end start