Table Of Contents

Creating a Timing Source for a Timed Loop

Last Modified: November 20, 2020

A timing source controls the execution of a Timed Loop.

  1. Open or create a VI that includes at least one Timed Loop on the diagram.
  2. Add Create Timing Source to the diagram. Configure the type and rate of the timing source using the pull-down menus that appear.
    Type Description

    A timing source that controls a Timed Loop using an internal clock. You can choose from the following built-in timing sources:

    • 1 kHz Clock—A clock that allows you to schedule a Timed Loop with millisecond resolution. By default, a Timed Loop uses the 1 kHz clock of the operating system as a timing source.
    • 1 MHz Clock—A clock that allows you to schedule a Timed Loop with microsecond resolution. If the controller does not support microsecond resolution due to processor or operating system limitations, the 1 MHz clock is not available.

    You can also select a built-in timing source by selecting the Timing Source border node on the Timed Loop and choosing a timing source in the Item tab.


    A timing source that triggers the start of a timed structure based on a software-defined event. You can use a software-triggered timing source for the following applications:

    • As a real-time-compatible event handler.
    • To notify a consumer Timed Loop when new data becomes available within a producer-consumer application.
    • For discrete event simulation.

    Use Fire Software-Triggered Timing Source to specify the number of ticks that elapse between each event.

  3. Wire timing source name of Create Timing Source to source in on the Timing Source border node of any Timed Loop that you want to control with the timing source you created.

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