void matrixkeyscan()
{
    uchar temp,key;
    P3=0xfe;
    temp=P3;
    temp=temp&0xf0;
    if(temp!=0xf0)
    {
        delayms(10);
        temp=P3;
        temp=temp&0xf0;
        if(temp!=0xf0)
        {
            temp=P3;                                     //这个不明白
            switch(temp)
            {
                case 0xee:
                key=0;
                break;
                case 0xde:
                key=1;
                break;
                case 0xbe:
                key=2;
                break;
                case 0x7e:
                key=3;
                break;
            }
            while(temp!=0xf0)              //等待按键释放
            {
                temp=P3;
                temp=temp&0xf0;
            }
            display(key);                    //显示
        }            
    }

请问那个地方为什么还要加一个temp=P3;???