Hi Preitano,
The tick count function simply takes a reading from a system clock. In this program, it looks like these functions are being used to compare the time between different iterations of the loop that is waiting to see if bytes are at the port. If the difference between the tick count inside the while loop and the tick count that executes before the loop begins exceeds the timeout input, then the loop will stop.
In order to see more of why this program is running more slowly than hyperterminal, you could use the VI Profile option if you have the Professional edition of LabVIEW. Simply go to Tools, then Advanced..., and then select VI Profile. This allows you to see how much time was spent in each part of your code. If you do not have the Pro edition, then you may be able to do a makeshift version of the same functionality by using the tick count function. You can place the tick count function different places in your code, and compare the times between certain steps. However, this might affect the speed of execution of the code, so it is not the best way to do this.
John M
Applications Engineer