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功能：同時(shí)按鍵搶答，先按的有效，其他按鍵鎖死，復(fù)位后進(jìn)行下一輪搶答

時(shí)間：2010—7—19

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#include<reg52.h>


sbit key1=P3^0;
sbit key2=P3^1;
sbit key3=P3^2;
sbit key4=P3^3;


main()
{
        bit Flag;
        while(!Flag)
        {

                if(!key1) 

                {

                        P1=0xFE;

                        Flag=1;

                }

                else if(!key2)

                {

                        P1=0xFD;

                        Flag=1;

                }
                else if(!key3)

                {

                        P1=0xFB;

                        Flag=1;

                }
                else if(!key4)

                {

                        P1=0xF7;

                        Flag=1;

                }
        }
        while(Flag);
}