Using the 10 MHz reference clock as a timing source for a timed loop

[Zog24]

Hi,

I'm having trouble getting to grips with a PCIe-6251 card. I know that the card has a built-in 10MHz reference clock (which uses an 80MHz timebase), which can be used to time analogue output signals, but according to the instruction manual should also be used to time digital output signals.

Is it possible to use the 10MHz reference clock, or any other timing source on the PCIe-6251 to control a timed loop? As far as I realize, you're meant to use the "DAQmx create timing source" VI, and connect that to the timing source input terminal of the timed loop, but which mode of the "DAQmx create timing source" VI should I use, to get it to work? I have tried using the NI Example finder, but none of the codes I've found seem to fulfil this specific task...

Thank you for any help provided.

[Zog24]

Just to clarify, my aim is to use the PCIe-6251 to time the timed loop, with a tick rate of 1MHz or more... so if there is an easier way to do that than using the 10MHz timebase, that would be even better.

[Coq_Rouge]

Is it possible to use the 10MHz reference clock, or any other timing source on the PCIe-6251 to control a timed loop? As far as I realize, you're meant to use the "DAQmx create timing source" VI, and connect that to the timing source input terminal of the timed loop, but which mode of the "DAQmx create timing source" VI should I use, to get it to work? I have tried using the NI Example finder, but none of the codes I've found seem to fulfil this specific task...

Thank you for any help provided.

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For a timed loop we have the following restrictions from the Labview help

Loop Timing Source—Specifies the type and name of the timing source for the Timed Loop. The Loop Timing Source settings include the following components: Source Type—Specifies an internal timing source to control the timed structure. In addition to the internal timing sources, this listbox includes any timing sources you configured on the system. 1 kHz Clock—Selects the 1 kHz clock of the operating system. Using the 1 kHz clock, a timed structure can execute an iteration once every 1 millisecond. All LabVIEW platforms that can run a timed structure support the 1 kHz timing source. 1 MHz Clock—Selects the 1 MHz clock supported on RT targets with Intel Pentium III or later-class processors. Using the 1 MHz clock, a timed structure can execute an iteration once every 1 microsecond.

It should also be noted that the software timer for standard Labview (non RT) is not very accurate. So for precise DAQ always use the internal clock on your DAQ board, and read/write buffered data in chunks. That will ensure accurate data sterams with no data glitches

[Zog24]

In the "configure timed loop" window there are two options: "use built-in timing source" (not suitable for my application as it is dependent on cpu load etc) and "use timing source terminal". My question is, how can I use the PCI-6251 to create a DAQmx timing source, that can be wired to the "use timing source terminal" input?

I have attached one of my failed attempts. When I run it, I get the following error message: Error -200452 occurred at DAQmx Create Timing Source (Control Loop From Task).vi:1

[Zog24]

Just noting, the version of Labview I use is Labview 2009, if that helps answering the question.