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.
