8255_1.asm

来自「51系列单片机的汇编程序包」· 汇编 代码 · 共 28 行

;=====================  8255 A.B.C口输出方波 ===================
        ORG 0580H
SE09:   MOV A,#55H              ;一位隔一位高电平
LO15:   MOV DPTR,#0FFFCH
        MOVX @DPTR,A
        INC DPTR
        MOVX @DPTR,A
        INC DPTR
        MOVX @DPTR,A            ;A.B.C口送入
        MOV R2,#40H             ;延时
        CALL DELY
        CPL A                   ;取反
        SJMP LO15               ;循环
;---------------------------------------------
DELY:   PUSH 02H
DEL2:   PUSH 02H
DEL3:   PUSH 02H                ;延时
DEL4:   DJNZ R2,DEL4
        POP 02H
        DJNZ R2,DEL3
        POP 02H
        DJNZ R2,DEL2
        POP 02H
        DJNZ R2,DELY
        RET
;---------------------------------------------
        END