Shafi,

First of all, you should give more details on your board here - most notably, what is the derivative you are using, what is your hardware (if you are using a proper RS232 level converter), what C-compiler are you using; and most importantly what is the frequency of crystal you are using.

Also, please read http://www.8052.com/faqs.phtml?FAQ=120199 and http://www.8052.com/users/jonled/noob.pdf on how to post code here properly.

Now for the errors.

I highlighted two lines which are more than suspicious...

Jan Waclawek

while(1) {
  for(i=0;i<27;i++) {
    SBUF=ch;
    if(TI==0) { }
    ch=ch+1;
    T1=0;
  }
  ch=0x41;
}