Marco:
The past several times that I ran your code through the Pinnacle simulator I had to make some minor changes in order for the program to run successfully. I had thought that the differences were because of different assemblers, editors, etc. One change I had to make was your statement SET TR1 which I am assuming (I know - very dangerous word!!) you are using to start Timer 1. In Pinnacle SET is not a command but a DIRECTIVE that assigns a value to a symbol. It may very well be the same for your assembler. According to my MCS-51 Users Manual you should be using the form SETB TR1 (Set Bit TR1). I'm wondering if your ommision of the 'B' might be the cause of your problem in that Timer 1 never starts.
When I try to compile your program with SET TR1 I get a syntax error msg.

Hang in there...

Hal