Structured Text Execution

Hi,
I am developing software for a new plant we are working on, hardware that we are using is APAX-5520KW PAC from Advantech. Up until now I only programmed using ladder/FBD and occasionally writing C scripts for customized functions. This particular project requires bit of a complicated control scheme with some motion control as well, which makes ST a preferable choice. This is also the first time I am using PAC (soft PLC) instead of regular PLC's
Now my questions regarding ST are

1. What determines the scan time of a program written in ST?
2. When a function is called in ST, does execution of parent function stops until the called function returns?
3. My hardware becomes unresponsive if I use a timer inside a WHILE loop, does this mean that the CPU stops execution of rest of program once it enters a WHILE loop?

Any other tips regarding ST, and links that provide examples will be greatly appreciated.
Thanks in advance,
Anas
C&M Engineering
www.pakplc.com

This may or may not apply to you, but i used this PDF which is for Allen Bradley controllers. Go through the FOR, WHILE loop instructions, it explains how they executed in the scan.

http://literature.rockwellautomation.com/idc/groups/literature/documents/pm/1756-pm007_-en-p.pdf

1 the number of instructions
2 yes but that is with all languages the same a processor can do only one thing at a time.
3 as long as the while is true yes.

get yourself a txt version of www.oscat.de

@ shooter, the link you provided is in german, english version?

it looks german but the files are in english just go to download manager.

im downloaded the OSCATBasic DOc. ENglish version 3.33, looks like their is a wealth of info in their, thanks shooter.