小白求助！！大神帮忙看一下那里的问题，S20的功能好像不大对。

#include <reg52.h>
#include <intrins.h>
#define uint unsigned int
#define uchar unsigned char
sbit button_S16=P3^6; //P3.6和P3.2控制按键S16
sbit button_S20=P3^6; //P3.6和P3.3控制按键S20
void delayms(uint);
uchar aa;
void main()
{
EA=1;
EX0=1;
EX1=1;
IT0=0;
IT1=0; //低电平触发
aa=0xfe;
while(1)
{
P1=aa;
delayms(500);
aa=_crol_(aa,1);
button_S16=0; //S16的P3.6端先置0
button_S20=0; //S20的P3.6端先置0
}
}
void delayms(uint xms)
{
uint i,j;
for(i=xms;i>0;i--)
for(j=110;j>0;j--);
}
void extre0() interrupt 0 //外中断 0
{
P1=0x00;
}
void extre1() interrupt 1 //外中断 0
{
P1=0x00;
}