Difference between time waiting functions

[Dejun]

Hello,

I am wondering what's the difference between 'wait (ms)' and 'Wait Until Next ms Multiple' functions, especially what's the difference when they are used in loops for delay. According to function helps, looks like the latter function has more advanced function, but I still have no idea what's the exact difference between them, especially in  selecting which one for which situation...

Thanks for advise.
 

Message Edited by Dejun on 10-03-2007 11:15 AM

[Kevin_Price]

Let me illustrate with a hypothetical example.  Let's suppose you have a loop containing code that takes anywhere from 7 msec to execute.  Let's further suppose that you use 10 msec delays with the two different functions, and that you enter your loop at t=2 msec.

Scenario A.  Sequencing is used to make sure code execution occurs first, then the delay will start.

1. With "Wait (msec)", the timing will look like:

Iteration i: 0,  1,  2

Code ends:   9, 26, 43

Wait ends:  19, 36, 53

2. With "Wait Until Next msec Multiple", the timing will look like:

Iteration i: 0,  1,  2

Code ends:   9, 19, 29

Wait ends:  10, 20, 30

Scenario B.  Delays are decoupled from code and execute in parallel

1. With "Wait (msec)", the timing will look like:

Iteration i: 0,  1,  2

Code ends:   9, 19, 29

Wait ends:  12, 22, 32

2. With "Wait Until Next msec Multiple", the timing will look like:

Iteration i: 0,  1,  2

Code ends:   9, 17, 27

Wait ends:  10, 20, 30

You are correct that proper selection depends on the situation.  Very generally, 'wait (msec)' is just a simple delay while 'ms multiple' helps you to sync to a metronome-like beat.  However, if you just barely miss a particular multiple, you get stuck waiting until the next one.

-Kevin P.

[Dejun]

Kevin, thank you soooooooooooo much for your so clear explanation !!!
-Dejun

[Kevin_Price]

Too late to edit, so here's a correction:

For Scenario A, part 2, the "Code Ends:" row should be 9, 17, 27 rather than 9, 19, 29.

-Kevin P.