8255a.asm

89s52+8255a控制一组指示灯循环发光

ORG 0000H
MOV DPTR,#7FFFH
MOV A,#89H
MOVX @DPTR,A
MOV A,#01H
MAIN:
MOV DPTR,#7CFFH
MOVX @DPTR,A
RL A
ACALL DEL
AJMP MAIN
DEL:
MOV R7,#04H
DEL1:
MOV R6,#0FFH
DEL2:
MOV R5,#0FFH
DJNZ R5,$
DJNZ R6,DEL2
DJNZ R7,DEL1
RET
END