Configure Next Iteration Dialog Box

LabVIEW 2016 Help

Edition Date: June 2016

Part Number: 371361N-01

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Requires: Base Development System (Windows)

Double-click the Right Data node of a Timed Loop or the Right Data node of the last frame of a Timed Loop with frames to display this dialog box. You also can right-click the Right Data node and select Configure Input Node from the shortcut menu to display this dialog box.

Use this dialog box to configure how a Timed Loop executes during the next iteration. You can specify a new period, priority, and other advanced options for the next iteration.

This dialog box includes the following components:

  • Period—Specifies the period for the next iteration of the Timed Loop. The default is -1, which means that the period is unchanged from the previous iteration. The period value specifies the amount of time that elapses between two subsequent iterations of the Timed Loop. The unit of the period changes depending on the timing source of the structure.
    Note: Do not set the period of a Timed Loop to 0. National Instruments does not support applications that contain Timed Loops with periods of 0 because these periods cause undefined application behavior. If you need a loop that runs as fast as possible combined with the priority execution features of a Timed Loop, use a While Loop inside a Timed Sequence structure instead.
  • Priority—Specifies the priority of the next iteration of the Timed Loop relative to other timed structures that are ready to execute. The higher the number you enter, the higher the priority of the Timed Loop over other timed structures. The value for Priority can be -1 or a positive integer between 1 and 65,535. The default is -1, which means that the priority is unchanged from the previous iteration.
    Note  These priorities are different from VI priorities. LabVIEW executes the timed structures at a priority level below the time-critical priority and above the high priority. The LabVIEW execution system is preemptive, so a higher priority timed structure that is ready to execute preempts all lower priority structures also ready to execute and other LabVIEW code not running at time-critical priority.
  • Advanced Timing—Specifies advanced timing options. The Advanced Timing settings include the following components:
    • Deadline—Specifies a time boundary for the completion of the next iteration of the Timed Loop. If the iteration does not complete before the specified Deadline, the Finished Late? [i-1] output on the Left Data node returns TRUE in the iteration that follows.
    • Offset / Phase—Specifies the starting time or phase for the next iteration of the Timed Loop. You can use this option to synchronize structures or align their phases. For example, you can configure two Timed Loops to use the same timing source instance by specifying the same name for Source name in the Loop Timing Source section of the Configure Timed Loop dialog box. In one Timed Loop, you can enter a value of 0 in Offset / Phase and in the other Timed Loop enter a value of 100. The Timed Loops execute at their respective periods, but 100 timing units separate their execution.
    • Timeout—Specifies the maximum amount of time, in milliseconds, the next iteration of the Timed Loop can wait for a trigger event from the structure timing source. If the next iteration does not begin to execute before the timeout value, the Timed Loop executes the iteration untimed and returns Timeout in the Wakeup Reason output on the Left Data node in the following iteration. The default is 0, which means that the timeout is unchanged from the previous iteration. Setting the timeout to -1 means the next iteration can wait indefinitely for a trigger event from the structure timing source.
  • Processor Assignment—Specifies the processor assigned to handle the next iteration. The Processor Assignment settings include the following components:
    • Mode—Specifies how to assign available processors to handle execution. The default is Automatic, meaning LabVIEW automatically assigns a processor to handle execution. You can select from the following options:
      • Automatic—LabVIEW automatically assigns a processor to handle execution. LabVIEW disables the Processor control and sets it to -2 when you select this option.
      • No Change—LabVIEW automatically assigns this frame to the processor that handled the previous frame execution. LabVIEW disables the Processor control and sets it to -1.
      • Manual—Allows you to manually select a processor to handle execution. You must enter a value between 0 and 255 in the Processor control to specify the processor you want to handle execution.
    • Processor—Specifies the processor you want to handle execution. The default is -2, which means LabVIEW automatically assigns a processor. To manually assign a processor, enter a number between 0 and 255, where 0 represents the first processor. If you enter a number that exceeds the number of available processors, you generate a run-time error and the timed structure does not execute.
  • Action on Late Iterations—Specifies the late iteration mode for the next iteration of the Timed Loop.
    • No Change—Configures a new action on late iterations for the next iteration of the Timed Loop if you remove the checkmark from this checkbox.
      • Discard missed periods—Ignores the data of the Timed Loop iterations for each missed schedule. Otherwise, the Timed Loop processes the data from the iterations that missed the specified schedule.
      • Maintain original phase—Adjusts a Timed Loop that executes late to the originally configured schedule. Otherwise, the Timed Loop defines a new schedule that starts at the current time.

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