Selecting a Time Reference

The selected time reference is used by NI-Sync to drive time on a device; in other words, NI-Sync matches the device's time to that of the device's selected time reference. Each device can have a maximum of one selected time reference. Complete the following steps to set a selected time reference:

Selecting a Time Reference for a PXI Module

  1. Place niSync Initialize.
  2. Select a PXI timing and synchronization module as the resource name for niSync Initialize.
  3. Place niSync Set Time Reference.
  4. Select an instance of niSync Set Time Reference. You can select GPS, IRIG, PPS, or 1588 Ordinary Clock using niSync Set Time Reference. You can also put the device in Free Running mode.

The time reference you chose with niSync Set Time Reference becomes the selected time reference for the device specified in resource name.

Tip Tip  For a more detailed example of selecting time reference for a PXI module in LabVIEW, refer to the Set Time Reference example, found in the Example Finder under Hardware Input and Output»Timing and Synchronization»Time-based»Set Time Reference.vi.
Note Note  You can set IRIG-B as the selected time reference only if you have an external device capable of generating an IRIG signal physically connected to the PXI chassis.

Selecting a Time Reference for a Linux RT Target

Unlike selecting a time reference for a PXI module, you cannot manually select a time reference on a Linux RT target. Instead, the most accurate time reference is automatically determined and selected for the user. However, you can manually enable or disable time references on a Linux RT target, allowing you to determine which time references are eligible to be selected. Only an enabled time reference can be the selected time reference.

Complete the following steps to enable and/or disable time references on a Linux RT target:

  1. Place niSync Initialize.
  2. Select a Linux RT device as the resource name for niSync Initialize.
  3. Place niSync Get Time References to retrieve a list of time references installed on the device.
  4. Place an niSync Property Node and select Active Item as the first property.
  5. Specify the time reference to enable or disable by wiring it from the output of niSync Get Time References to Active Item.
  6. Expand the niSync Property Node and select Time Reference Enabled (niSync»Timing»Time Reference»Time Reference Enabled) as the second property.
  7. Right-click the Time Reference Enabled property and select Change to Write.
  8. Enable or disable the time reference:

The time reference connected to Active Item is either enabled or disabled. An enabled time reference is eligible to be chosen as the selected time reference.


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