sx.txt

8路竞赛抢答器

MY_DATA 	SEGMENT	
P8255_A    	    DW  	0C400H  	
P8255_B     	DW  	0C401H
P8255_C     	DW  	0C402H
P8255_MODE      DW  	0C403H
KL		        DB		?
LED             DB     0C0H,09FH,0A4H,0B0H,099H,92H,82H,0F8H
                DB     080H,90H,88H,83H,0C6H,0A1H,86H,8EH
MY_DATA 	ENDs
MY_CODE 	SEGMENT 
     ASSUME 	CS:MY_CODE,	DS:MY_DATA				
START: 	        MOV	AX,MY_DATA
		        MOV	DS,AX
	            MOV DX,P8255_MODE
       		    MOV AL,90H                   ;写8255控制字
       		    OUT DX,AL  
       		    
         	    
START1:	        MOV	CX,04H	                 ;显示器个数
		MOV	KL,01H	                 ;选中的显示器
START2:         MOV DX,P8255_A
                IN  AL,DX
                AND     AL,80H
                JNZ     START3
                MOV     DX,P8255_B
                MOV     AL,0FFH
                OUT     DX,AL     
                JMP     START2
START3:         MOV     DX,P8255_B    
                MOV     AL,FDH 
                OUT     DX,AL
                MOV    DX,P8255_A    
                IN      AL,DX
	        AND      AL,7FH
	        OR       AL,AL            ;比较是否为0
                JZ      START3  
                
START4:         MOV     BL,0
    	        MOV     CX,7
                SHR     AL,1
                JC    START5
                INC    BL
                LOOP   START4
                MOV    BL,0
                JMP    START4
START5:         MOV     DX,P8255_B
                MOV     AL,FEH
                OUT     DX,AL  
                MOV     AL,BL
                MOV     AL,KL
                MOV     DX,P8255_C
                MOV	AL,LED[BX]
                OUT     DX,AL
                JMP    START2 
EXIT:           MOV AX,4C00H
                INT 21H
MY_CODE		ENDS
         END	START