8255.asm

 IO8255_MODE  EQU       28BH
    IO8255_A  EQU       288H
    IO8255_B  EQU       289H
    IO8255_C  EQU       28AH

      CODE  SEGMENT
              ASSUME    CS: CODE
      START:  MOV       DX, IO8255_MODE         ;8255初始化
              MOV       AL, 89H ; INPUT
              OUT       DX, AL
      INOUT:  MOV       DX, IO8255_C           ;读入数据
	
		  IN	      AL, DX ; INPUT

              MOV       DX, IO8255_A           ;输出数据
	
		  OUT       DX, AL

              MOV       DL,0FFH     ;判断是否有按键
              MOV       AH, 06H
              INT       21H
              JZ        INOUT       ;若无,则继续

              MOV       AH,4CH      ;否则返回
              INT       21H

      CODE  ENDS
              END       START