12编写实验程序，利用8255的输出来控制步进电机的运转

单片机的
C8255 EQU 8406H
D8255C EQU 8404H
D8255A EQU 8400H
SPDTR EQU 20H
STEPPT EQU 21H
DIRL EQU 22H
DIRH EQU 23H
SWITCH EQU 24H

ORG 0000H
LJMP START
ORG 000BH
LJMP RUNINT
ORG 0100H
START:
MOV SP,#40H
LCALL INIT
LCALL CHKSWITCH
SJMP $-3
INIT:
CLR EA
MOV DPTR,#C8255
MOV A,#90H
MOVX @DPTR,A
MOV DPTR,#MRSTEP
MOV DIRH,DPH
MOV DIRL,DPL
MOV SPDTR,#00H
MOV SWITCH,#00H