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Digital Subsystem Channels

Digital subsystems transfer digital or logical values in bits via digital lines. You can perform clocked and non-clocked digital operations using the DataAcquisition interface in the Data Acquisition Toolbox™.

Add lines of the digital subsystem as channels to your DataAcquisition using addinput, addoutput, or addbidirectional. Digital channels can be:

  • InputOnly: Allows you to read digital data.

  • OutputOnly: Allows you to write digital data.

  • Bidirectional: Allows you to change the direction of the channel to read or write data. You can set the direction to Input or Output. By default the direction is Input.

Digital Clocked Operations

With clocked operations, you can acquire or generate clocked signals at a specified scan rate for a specified duration or number of scans. These operations use hardware timing to acquire or generate at specific times. The operation is controlled by events tied to subsystem clocks. In a clocked acquisition, data is transferred from the device to your system memory and displays when the event calls for the data. In signal generation, data generated from the device is stored in memory until the configured event occurs. When an event occurs, data is sent via the digital channels to the specified devices.

Digital systems do not inherently have a clock. You can synchronize data by adding a clock in one of these ways:

Access Digital Subsystem Information

This example shows how to access the device digital subsystem information and find line and port information using daqlist.

Find devices connected to your system and find the NI model USB-6509 device.

dev = daqlist("ni")
dev =

  2×4 table

    DeviceID                Description                  Model             DeviceInfo       
    ________    ___________________________________    __________    _______________________

     "Dev2"     "National Instruments(TM) USB-6509"    "USB-6509"    [1×1 daq.ni.DeviceInfo]
     "Dev3"     "National Instruments(TM) USB-6211"    "USB-6211"    [1×1 daq.ni.DeviceInfo]

View the subsystem information in the DeviceInfo for Dev2 using index 1.

DevInf = dev.DeviceInfo(1)
DevInf = 

ni: National Instruments(TM) USB-6509 (Device ID: 'Dev2')
   Digital IO supports:
      96 channels ('port0/line0' - 'port9/line7')
      'InputOnly','OutputOnly','Bidirectional' measurement types

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