Hi Praveen,
Can you please tell me how exactly you are
testing the timer ? Also, note that timer
mode 1 is incremental. So if you set TH1 = 0xFF
and TL1 = 0xFF then it will overflow in the next
machine cycle once it is started. So, you might
not notice the delay at all. The timer tutorial
on this site is very nice and useful and clearly
tells you how these timers work.

http://www.8052.com/tuttimer.phtml

regards
Ashish