;***********************************;
;*    十字路口紅綠燈模擬演示程序   *;
;* 端口各燈的設置:                 *;
;*   1紅 1黃 1綠 0 0 2紅 2黃 2綠   *;
;***********************************;
data segment
ioport          equ 0c400h-0280h
io8255a         equ ioport+28ah
io8255b         equ ioport+28bh
portc1  db  24h,44h,04h,44h,04h,44h,04h   ;六個燈可能
	db  81h,82h,80h,82h,80h,82h,80h   ;的狀態數據
	db  0ffh                          ;結束標志
data ends
code  segment
      assume  cs:code,ds:data
start:
	mov   ax,data
	mov   ds,ax
	mov   dx,io8255b
	mov   al,90h
	out   dx,al           ;設置8255為C口輸出
	mov   dx,io8255a
re_on:  mov   bx,0
on:     mov   al,portc1[bx]
	cmp   al,0ffh
	jz    re_on
	out   dx,al           ;點亮相應的燈
	inc   bx
	mov   cx,800h          ;參數賦初值
	test  al,21h          ;是否有綠燈亮
	jz    de1             ;沒有,短延時
	mov   cx,0efffh         ;有,長延時
de1:    mov   di,0fff0h         ;di賦初值5000
de0:    dec   di              ;減1計數
	jnz   de0             ;di不為0
	loop  de1
	push dx
	mov ah,06h
	mov dl,0ffh
	int 21h
	pop dx
	jz  on                ;沒有,轉到on
exit:   mov   ah,4ch          ;返回
	int   21h
code ends
	end start