#include<reg51.h>
unsigned char temp[]={'1','2','3','a','b','c'};
unsigned char i;
void initial()
{
 TMOD=0x20;
 TH1=0xf3;
 TL1=0xf3;
 ET1=1;
 TR1=1;
 TR0=1;
 EA=1;
 SCON=0x50;
 ES=1; 
 }
void main()
{initial();
 while(1)
 {
  SBUF=temp[i];
   while(!TI);
   TI=0;
   i++;
   if(i==5){i=0;}
 }
}