4b_8255输入、输出.asm

来自「单片机杭州天煌教仪自带例程单片机杭州天煌教仪自带例程」· 汇编 代码 · 共 26 行

            ;8255 PortB 输入 PortA 输出           
             PORTA equ  7CFFh  ; Port A
             PORTB equ  7DFFh  ; Port B
             PORTC equ  7EFFh  ; Port C
             CADDR equ  7FFFh  ; 控制字地址
             ORG   0000H
             LJMP   MAIN
             ORG   0030H  
MAIN:        MOV   A,#82H      ; 方式0，PA，PC输出，PB输入
             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