#include <reg51.h>
unsigned char led[]={0xfe,0xfd,0xfb,0xf7,0xef,0xdf,0xbf,0x7f};
unsigned char Recbyte;
void delay(unsigned int t)
{
While(t--);
}

void sx()
{
int I;
for(i=0;i<8;i++)
{
P1=led[i];
delay(30000);
}
}

void xs()
{
int I;
for(i=7;i>=0;i--)
{
P1=led[i];
delay(30000);
}
}

void ss()
{
P1=0x00;
delay(30000);
P1=0xff;
delay(30000);
}

void sendbyte(unsigned char i)
{
SUBF=i;
while(!TI);
TI=0;
}

void main()
{
TMOD=0x20;
TL1=0xfd;
TH1=0xfd;
TR1=1;
SCON=0x40;
PCON=0x00;
EA=1;
ES=1;
REN=1;
Recbyte=0;
while(1)
{
switch(Recbyte)
{
case’A’:sx();Recbyte=0;break;
case’B’:xs();Recbyte=0;break;
default:ss();
}
}
}  

void ser1() interrupt 4
{
EA=1;
RI=0;;
Recbyte=SBUF;
sendbyte(Recbyte);
EA=1;
}