;8155輸入、輸出

             mode   equ  01H    ; 方式0，PA輸出,PB輸入
             PortA  equ  7F01h  ; Port A
             PortB  equ  7F02h  ; Port B
             PortC  equ  7F03h  ; Port C
             CAddr  equ  7F00h  ; 控制字地址

             org   0000H                   
             LJMP   MAIN
             ORG    0030H 
 
MAIN:       
             MOV   A,#MODE
             MOV   dptr,#CADDR
             MOVX  @dptr ,A
loop:        MOV   DPTR,#PORTB             
             MOVX  A,@DPTR
	     MOV   DPTR,#PORTA
             MOVX  @DPTR,A
	     CALL   DELAY
             SJMP  loop
Delay:
       mov   r6, #0
       mov   r7, #0
DelayLoop:
       djnz  r6, DelayLoop
       djnz  r7, DelayLoop
       ret

             end