WHy not try a transmitt loop like the one below. And in any case pay heed to Steve's suggestion. Simulating Timer interrupts on Simulator needs lots of innovation!
If all is well the code below will transmitt 55 repeatedly at 1200 Baud with a 16Mhz crystal.

org 00h
jmp SLCHK

SLCHK: mov scon, #40H
      mov tmod, #20H
      mov th1, #0DDH
      mov tcon, #40H
      clr TI
LUP:  mov sbuf, #55h
      jnb TI, $
      clr TI
      jmp LUP

      End

Good luck

Raghu