Synchronization

Synchronization is important to minimize skew between channels and to eliminate clock drift between modules in long-duration operations.

Some applications require tight synchronization between input and output operations on multiple modules. Synchronization is important to minimize skew between channels and to eliminate clock drift between modules in long-duration operations. You can synchronize the analog input operations on two or more PXIe-4309 modules to extend the channel count for your measurements.
Note the PXIe-4309 can also synchronize with 62XX and 63XX devices/modules, such as the PXI-6289 and PXIe-6363, respectively.

Reference Clock Synchronization

With reference clock synchronization modules generate their ADC sample clock from the shared 100 MHz reference clock on the PXIe backplane (PXIe_CLK100). The backplane supplies an identical copy of this clock to each peripheral slot. In addition, multiple chassis can be synchronized by using a timing and synchronization board to lock the 100 MHz clock across chassis.

When acquiring data from multiple modules within the same NI-DAQmx task, NI-DAQmx automatically handles all of the Reference Clock Synchronization details required to synchronize the modules within the task. This is known as a multi-device task.

To perform reference clock synchronization when using multiple NI-DAQmx tasks that are acquiring at the same rate, complete the following steps to synchronize the hardware.
  1. Specify PXIe_CLK100 as the reference clock source for all modules to force all the modules to lock to the reference clock on the PXIe chassis.
  2. Choose one module to provide the start trigger.
  3. Configure the rest of the modules in your system to receive their start trigger from the start trigger module. This ensures that all modules will begin returning data on the same sample.
  4. Set the synchronization type of the modules receiving the Start Trigger at DAQmx Trigger»Advanced»Synchronization»Synchronization Type to Slave and the module providing the start trigger to Master.
  5. Start all of the modules using the start trigger. This sets them up to expect the master start trigger.
  6. Start the master start trigger module task. You can now acquire data.
Note Consider using a multi-device task when synchronizing multiple devices at the same rate.
Note You can find example VIs in the NI Example Finder. Select Help»Find Examples to launch the NI Example Finder.