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C Series Multidevice Tasks

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    Last Modified: November 16, 2017

    When you include channels from multiple C Series modules in a task, NI-DAQmx automatically synchronizes the modules. A task can include channels from multiple C Series modules, given the following conditions:

    • All channels in the task must be of the same I/O type. Multiple counter I/O channels are only allowed for Devices That Support Multi-Counter Tasks.
    • If the task includes channels from a mixture of C Series Delta-Sigma devices, you must account for filter delay differences between the devices. This delay is also known as the input delay. Refer to your device specifications for the value.
    • The modules must all be in the same NI CompactDAQ chassis or meet the conditions for multichassis device tasks.
    spd-note-
    ni__notes  
    • AI tasks containing only 16-bit or lower resolution AI modules use half the USB bandwidth of tasks with 24-bit AI modules.
    • The format of raw data returned by a C Series AI task varies depending on if any 24-bit AI modules are in the task and might not correspond to the order of the channels in the task. Scaled or unscaled data is preferable to raw data with the NI CompactDAQ chassis.
    • The acquisition mode of the NI 9775 will vary depending on the other modules in the task. If the task uses only NI 9775 modules, all the modules can operate in Record Mode. If the task uses an NI 9775 module and other types of modules, the NI 9775 operates in Continuous Mode.

    C Series Multichassis Device Tasks

    A task can include channels from multiple C Series modules in separate CompactDAQ chassis, given the following conditions:

    • Network-synchronized chassis[1] must be part of the same time-synchronized network. Refer to the device specifications for supported synchronization protocols and topologies.
    • Chassis that are not network-synchronized must be connected through a NI 9469.
    • If a task has a network-synchronized chassis and connections through the NI 9469 to chassis that are not synchronized, the first channel in the task must be in the network-synchronized chassis along with the NI 9469 connection to other chassis that are not synchronized.
    • When using signal-based synchronization using the NI 9469, the first channel in the channel list must be on a module in the master chassis. The master chassis is determined by the physical configuration of the chassis connections, and it should be able to output signals to the slave chassis.
    • If an Analog Input task contains Delta-Sigma modules, a channel on a Delta-Sigma module in the master chassis needs to be first on the channel list.
    • If an Analog Input task contains a device with a reference clock, a channel from a reference-clocked device needs to be first on the channel list.
    • Multichassis device tasks are not supported in the cRIO-9040, 9041, 9042, 9043, 9044, 9045, 9046, 9047, 9048, and 9049.

    Exceptions

    • The NI 9361 does not support multichassis device tasks.
    • The NI 9260 must drive the idle output to zero. If you don't, you will receive an error.
    • The NI 9775 does not support multichassis device tasks.
    • 1 Network-synchronized devices include the cDAQ-9185 and 9189.

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