void delay(){
int i,j;
for(i=0;i<10;i++){
for(j=0;j<120;j++);
}
}
void button_scan(){
int temp1=0,temp2=0,temp=0;
P1=0x0f;
if(P1!=0x0f){
delay();
temp1=P1;
P1=0xf0;
if(P1!=0xf0){
delay();
temp2=P1;
}
}
temp=temp1+temp2;
switch(temp){
case 0xee:P2_0=1;break;
case 0xed:P2_1=1;break;
case 0xeb:P2_2=1;break;
case 0xe7:P2_3=1;break;
case 0xde:P2_4=1;break;
case 0xdd:P2_5=1;break;
case 0xdb:P2_6=1;break;
case 0xd7:P2_7=1;break;
case 0xbe:P2_4=0;break;
case 0xbd:P2_5=0;break;
case 0xbb:P2_6=0;break;
case 0xb7:P2_7=0;break;
case 0x7e:P2_4=(~P2_4);break;
case 0x7d:P2_5=~P2_5;break;
case 0x7b:P2_6=~P2_6;break;
case 0x77:P2_7=~P2_7;break;