i've maked this post because Erik said in a reply:

"i've concerned master/slave. the idea is to connect more or less 1 master and 6 slaves then this is a bad title"

i'm trying to be clear, maybe using the first subject "serial communication betwwen 2 at89c52" and adding 5 more at89c52 make it confusing.

about the:

You still don't get it. You must wait until the first char is completely sent out of the UART before you send a new one. You must wait for TI to become 1.

you said too:

That's because you haven't paid attention to my comment. Using

  SBUF = x;
  while (TI==1);
  SBUF = y;
  while (TI==1);

Is virtually the same as

  SBUF = x;
  SBUF = y;

Especially as you clear TI in the interrupt!

so the true is i don't understand you what is going wrong. can you tell me more cleary, please be patience i'm new in this.

thanks,

Ruben Porras