Problems with serial port interface

[lionelgreenstreet at gmail.com]

Ok, 
thanks for your reply.
But i have another problem: i hadn't always the hardware needed for the tests. Before i've used a terminal and com0com to simulate a serial input: if i want to simulate a transmission every 5ms how can i do? I need a program or a code that i'm sure about its correctness. Another question: may i have some problems (for example timings) to simulate with the same pc a serial transmission? Any suggestion?
Thanks