矩阵键盘控制蜂鸣器程序，有点问题帮忙检查下

#include<reg52.h>
#define uint unsigned int
#define uchar unsigned char
uchar aa;
sbit BEEP=P2^3;
void beep(uchar x)
{ uint j,i;

for(j=(250*x);j>0;j--)
{ for(i=500;i>0;i--);
BEEP=~BEEP;
}
void delayms(uint x)
{
uint i,j;
for(i=x;i>0;i--)
for(j=110;j>0;j--);
}
void matrixkeyscan()
{
uchar temp;
P3=0xfe;
temp=P3;
temp=temp&0xf0;
if(temp!=0xf0)
{
delayms(10);
temp=P3;
temp=temp&0xf0;
if(temp!=0xf0)
{
temp=P3;
switch(temp)
{
case 0xee:
aa=1;
break;
case 0xde:
aa=2;
break;
case 0xbe:
aa=3;
break;
case 0x7e:
aa=4;
break;
}
while(temp!=0xf0)
{
temp=P3;
temp=temp&0xf0;
}
beep(aa);
}
}
P3=0xfd;
temp=P3;
temp=temp&0xf0;
if(temp!=0xf0)
{
delayms(10);
temp=P3;
temp=temp&0xf0;
if(temp!=0xf0)
{
temp=P3;
switch(temp)
{
case 0xed:
aa=5;
break;
case 0xdd:
aa=6;
break;
case 0xbd:
aa=7;
break;
case 0x7d:
aa=8;
break;
}
while(temp!=0xf0)
{
temp=P3;
temp=temp&0xf0;
}
beep(aa);
}
}
P3=0xfb;
temp=P3;
temp=temp&0xf0;
if(temp!=0xf0)
{
delayms(10);
temp=P3;
temp=temp&0xf0;
if(temp!=0xf0)
{
temp=P3;
switch(temp)
{
case 0xeb:
aa=9;
break;
case 0xdb:
aa=10;
break;
case 0xbb:
aa=11;
break;
case 0x7b:
aa=12;
break;
}
while(temp!=0xf0)
{
temp=P3;
temp=temp&0xf0;
}
beep(aa);
}
}
P3=0xf7;
temp=P3;
temp=temp&0xf0;
if(temp!=0xf0)
{
delayms(10);
temp=P3;
temp=temp&0xf0;
if(temp!=0xf0)
{
temp=P3;
switch(temp)
{
case 0xe7:
aa=13;
break;
case 0xd7:
aa=14;
break;
case 0xb7:
aa=15;
break;
case 0x77:
aa=16;
break;
}
while(temp!=0xf0)
{
temp=P3;
temp=temp&0xf0;
}
beep(aa);
}
}
}
void main()
{
while(1)
{
matrixkeyscan();
}
}