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Running DAQmx Tasks Simultaneously

Updated Jun 5, 2019

Reported In

Hardware

  • Multifunction I/O Device

Software

  • LabVIEW
  • Measurement & Automation Explorer (MAX)

Driver

  • NI-DAQmx

Issue Details

  • I have a PXI/PXIe DAQ, PCI/PCIe DAQ card or an USB DAQ device (63XX, 62XX, 61XX and 60XX Series devices). How many DAQmx tasks of each kind can I run simultaneously on the same device?

Solution

In a multifunction DAQ device, the total number of possible concurrent tasks typically depends on whether you are running tasks that use hardware timing or software (on demand) timing.
 

Hardware-Timed Tasks

Hardware-timed tasks require timing information from the System Timing Controller to use for sample clocks, reference clocks, triggers, etc. The following table illustrates the number of hardware-timed tasks available to the user.

 

Hardware-Timed Tasks
# of Tasks per Device
Analog Input1
Analog Output1
Counter InputN††
Counter OutputN††
Digital Input1
Digital Output1
 

Software-Timed Tasks

Most software-timed tasks do not require a signal from a System Timing Controller in order to run. Software-timed means the host computer is controlling how often a sample is read from or written to the module.

 
Software-Timed (On Demand) Tasks# of Tasks per Device
Analog Input1
Analog Output1 Task for each AO channel†††
Counter InputN††
Counter OutputN††
Digital Input1 Task for each digital line capable of Digital Input
Digital Output1 Task for each digital line capable of Digital Output


It is possible to have Hardware and Software tasks running simultaneously, considering the maximum number of tasks for each timing mode.

††The number of counter tasks is always limited by the number of counters you have. Depending on whether you are using a counter task that uses multiple counters (like measuring frequency using the two counter method), you may be restricted to less counter tasks. To determine if you need one or two counters for your counter task, refer to How Many Counters Does Each Type of Counter Task Require?

†††67xx Cards have one DAC for every four channels, so for these cards you only have one task for every 4 AO channels. In LabVIEW, you will sum them up in a style like Dev1/ao0:3, Dev1/ao4:7, ... For other languages you use a similar syntax.

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