Table Of Contents

Timing Considerations for C Series Devices

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    Last Modified: November 16, 2017

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    Note  

    C Series devices do not support hardware-timed single-point sample mode or Wait for Next Sample Clock.

    Analog Input Timing Considerations for C Series Devices

    You can use multiple analog input devices of different types in the same task, and NI-DAQmx automatically synchronizes them.

    NI-DAQmx supports:

    • Only one analog input task at a time per NI cDAQ-9171, 9181, and 9191 chassis.
    • Up to three analog input tasks at a time per cDAQ-9132, 9133, 9134, 9135, 9136, 9137, 9138, 9139, 9174, 9178, 9179, 9184, 9185, 9188, 9188XT, and 9189 chassis.
    • Up to eight analog input tasks at a time per cRIO-9040, 9041, 9042, 9043, 9044, 9045, 9046, 9047, 9048, and 9049 chassis.

    Analog Output Timing Considerations for C Series Devices

    Only one hardware-timed analog output task per CompactDAQ chassis at a given time is supported, but the number of concurrent software-timed analog output tasks is limited only by the available channels. A single C Series analog output device cannot be used for hardware-timed and software-timed tasks at the same time.

    CompactRIO chassis can support more than one hardware-timed AO task per CompactRIO chassis. Refer to cRIO-904x Timing Engines.

    Digital Input/Output Timing Considerations for C Series Devices

    Only one hardware-timed digital input task and one hardware-timed digital output task per CompactDAQ chassis at a given time is supported, but the number of concurrent software-timed digital I/O tasks is limited only by the available lines.

    Refer to Digital I/O Considerations for C Series for more information about hardware-timed digital input/output.

    CompactRIO chassis can support more than one hardware-timed digital input task and one hardware-timed digital output task per CompactRIO chassis. Refer to cRIO-904x Timing Engines.

    Configurable Timing for C Series Devices

    On the NI 9207, NI 9208, NI 9209, NI 9212, NI 9213, NI USB-9213, NI WLS-9213, NI ENET-9213, NI 9214, NI 9216, NI 9217, NI 9219, NI WLS-9219, NI ENET-9219, NI 9224, NI 9226, NI 9228, and NI 9775, you can configure high-speed or high-resolution measurements using the AI.ADCTimingMode attribute/property.

    On the NI 9212, NI 9219, NI USB-9219, NI WLS-9219, and NI ENET-9219, you can also configure low-noise measurements using the AI.ADCTimingMode attribute/property.

    Default Settings for the AI.ADCTimingMode Attribute/Property

    For all modules in the cRIO-9040, 9041, 9042, 9043, 9044, 9045, 9046, 9047, 9048, and 9049 controller, the default value in hardware-timed mode is automatically determined based on Sample Clock Rate.

    For the NI 9207, NI 9208, NI 9209, NI 9212, NI 9213, NI USB-9213, NI WLS-9213, NI ENET-9213, NI 9214, NI 9216, NI 9217, NI 9219, NI WLS-9219, NI ENET-9219, and NI 9226 in CompactDAQ, the AI.ADCTimingMode attribute/property is set to High Resolution by default. To increase the conversion rate, set this attribute/property to High Speed.

    For the NI USB-9219, this attribute/property is set to High Resolution by default in on-demand mode, and the default value in hardware-timed mode is automatically determined based on Sample Clock Rate. To increase power line noise rejection on the NI 9212 and NI 9219, set this attribute/property to Best 60 Hz Rejection or Best 50 Hz Rejection.

    For the NI 9224 and NI 9228, this attribute/property is set by default to Automatic, which causes the module to sample with the highest resolution timing mode that is faster than the rate you specified.

    For the NI 9775, this attribute/property has a default timing mode of Automatic. The Automatic timing mode automatically configures the module to sample with the highest resolution timing mode that is compatible with the user-specified rate. If the AI.Lowpass.Enable attribute/property is set to false, the timing mode will remain in High Speed regardless of the user-specified sample rate.

    Slow sample modules are able to sample just fast enough to avoid returning repeated data. If the user-specified rate is above the maximum rate, the module will enter background convert and return repeated data. Slow sample modules on the cDAQ-9171 and cDAQ-9191 chassis have a default timing mode of Automatic.

    The AI.ADCTimingMode attribute/property affects both the maximum and default values for AIConv.Rate attribute/property in the DAQmx Timing property node. For instance, if the ADC timing mode corresponds to a conversion time of 200 ms, the maximum conversion rate is 5 Hz.

    Counter Input Timing Considerations for C Series Devices

    For the NI 9361, you can use multiple counter input devices in the same task, and NI-DAQmx automatically synchronizes them. A single NI 9361 cannot be used for hardware-timed and software-timed tasks at the same time. The cDAQ-9132, 9133, 9134, 9135, 9136, 9137, 9138, 9139, 9174, 9178, 9179, 9184, 9185, 9188, 9188XT, and 9189 chassis support up to four of the onboard chassis counters at a time.

    Implicit timing is not supported on the NI 9361.


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