LABVIEW HANDOUT 8
CHAPTER 8: THE SEQUENCE STRUCTURE
Build an event timer to compare the performance of For Loops and While Loops. Open a Blank
VI and name it Loop Timer (Sequence). The Front Panel is as follows:
Change the data-type representation of the Number of Elements Control and the For Loop
Array and While Loop Array Indicators to I32. Format the For Loop Time (ms) and While
Loop Time (ms) Indicators to U32. Place a Flat Sequence Structure on the Block Diagram:
Functions>>Programming>>Structures>>Flat Sequence Structure
Additional panes can be created by right-clicking on the border and clicking on Add Frame
After. Create the following VI:
Set the value of Number of Elements to 5 and use the Highlight Execution button to show the
data dependency of the program execution. Turn off the Highlight Execution function and set
the value of Number of Elements to that shown below and run the program:
Write the following event timer that uses artificial data dependency to control the order of
execution. Make a copy of the Loop Timer (Sequence) VI and name it Loop Timer (Data
Dependency). Eliminate the Flat Sequence Structure by right-clicking on the border and
selecting Remove Sequence. Construct the following VI, but do not change the Front Panel:
Set the Number of Elements to 10 and use the Highlight Execution function to demonstrate the
behavior of the program. Instead of using a Sequence Structure enclosing each loop, this
program uses artificial data dependency to control the order of execution. In the artificial data
dependency scheme, the mere arrival of data, with no regard to its actual value, triggers the
execution of a node. For instance, the While Loop cannot start until both inputs arrive. Also, the
Tick Count (ms) function does not engage until the data from the For Loop Start arrives at the
Sequence Structure. Turn off the Highlight Execution function and reset the value of Number
of Elements to that from the previous VI and run the program. The results should be the
approximately the same.