Does the 49days return-to-zero problem of Timer() function exist in CVI7.1 ?

[captainst]

Hello Everyone,

I have read here in forum problems concerning the reset of Time() function after 49 days of continous program running from the first time when the Timer() function is called.

I am using CVI 7.1 in my project, and this is very critical to the whole project. Does anybody know if this problem exists also on CVI 7.1 ?

Thanks!

[RobertoBozzolo]

As you can see in this thread, the problem existed in the past and NI tells now it should not exist in standard UI timers and in Timer () function; my experience is that it does exist in asyncronous timers.

Luis has started a test to see if it has effectively been corrected at least in standard UI timers and in Timer () function (I am confident it actually is 😞 we'll see if it is but I'm afraid results will arrive not before 40-45 days...

[captainst]

Ciao Roberto

Thanks for the reply. However, as can be seen from here:

http://digital.ni.com/public.nsf/allkb/2f80bef68dc8b1e2862563530068f0ca

or NI Document ID: 0MND339A

It says "In order to not to lose precision, CVI's function does not correct for this wraparound". Moreover, I noticed that this document has been updated 2004-12-07, that is after CVI 7.1 has been released I suppose. I doubt if NI indend to make correction on this.

I will submit an engineering support request to see what happens

[RobertoBozzolo]

Good shot captainst! I hadn't read this document before: according to it even UI timers are based on multimedia timers as async timers are...

I was always told that UI timers are NOT based on multimedia timers, as Luis itself seems to state in his replies in the thread I linked. Now... I really don't know what to say! Let's hope Luis explains us something more about this subject. Even though, timer rollover if sure and known is not so difficult to handle, at the price of a little care in every place we are using it in our programs...

Keep us informed about the results of your support request

Ciao

[LuisG]

The document that you cite is not relevant for recent versions of CVI. Notice that it list the software version as 4.0, which is very old. The rollover problem in UI timer controls and in the Timer function was eliminated back in version 5.0 or 5.5. I started a test the other day to confirm this.

Roberto, the Timer function (and the UI timer controls) internally use the Windows performance counter (if you're curious, look up QueryPerformanceCounter). The asynchronous timers, on the other hand, do use the Windows multimedia timer. You can actually find out exactly how the asynchronous timers are implemented (see toolslib\toolbox\asynctmr.c). Asynchronous timers might very well have a rollover problem still today.

Luis