thanks Hal, I am so confuse, I think I am clearing TI or RI by software not by hardware, when I use SCON I am telling. I read that 8051's family have all the structure to handle TI and RI, we just send information to SBUF and it can handle so easy. At this moment I am so confuse then. Can sent my program by e-mail ? you could run at your simulator, this program can send to ASCII characters to SBUF. After swith Vcc & ground at P3.1 pin at simulator the program begin to send information to the SBUF that's works, I will do again in the EPROM a see what happens