Wait on Digital Trigger Option for LabVIEW FPGA

Updated Mar 28, 2023

Reported In


  • NI-9469
  • NI-9401
  • CompactRIO Controller
  • CompactRIO Chassis


  • LabVIEW FPGA Module
  • LabVIEW Real-Time Module
  • LabVIEW

Issue Details

  • I use NI 9469 Synchronization module. How can I synchronize between 2 chassis using any trigger option in LabVIEW FPGA?
  • I use NI 9401 digital module with other anolog module. If I wanted to synchronize these modules with NI 9401 trigger source in each different loop, how can I do? 
  • What is 'Wait On Rising Edge' in FPGA I/O Method Node? 


NI Digital module support 'wait on digital trigger' in LabVIEW FPGA I/O Method Node. Generally, This method uses for synchronization of seperated other I/O or module, or especially chassis. To use this, follow below things. 
  1. Create FPGA I/O Method Node from LabVIEW FPGA function palette. 
  2. Rigth click and Select Item»FPGA Target»Which digital Module I/O channel you configured.
  3. Then, you can choose several options for method like below figure. This options depend on what signal characteristics you observe. 

Used Primarily to synchronize two modules with different sampling rates. For examples, when synchronization between analog modules and digital modules is required, the analog module can configure the edge of the digital signal to wait if it cannot be read from a single FPGA I/O node. This example is below. 

This is an example that does the following: When rising edge of digital signal generated in channel0 of Mod1, 1V is output in Channel0 of Mod3, and when falling edge, 0V is output.

Additional Information

There are examples this similar usage of this method node, Even though it not a dedicated module for Digital I/O. In chassis to chassis synchronization using NI 9469, you can refer to LabVIEW basic example, '9469 synchronization.lvproj'.

This FPGA I/O method sends and waits trigger signals to synchronize measurements or generations between Master and slave devices.