Checking if an Asynchronously Called VI is Currently Running

Issue Details

• I have dynamically called a VI using the Start Asynchronous Call node. How can I check if this VI is still running?

• I am trying to check if an asynchronously called VI has finished by checking the Execution:State property of the dynamically called VI, but this always returns "Running".

Solution

After starting an asynchronous call to another VI using the Start Asynchronous Call node, you can pass the reference out of this to a Wait on Asynchronous Call function. This function will run until the called VI has finished. When using this function, you must set the "options" input to 0x100 (Hexadecimal) when the reference to the VI is first opened. An example of this is shown below:

If you require a non-blocking method for determining if an another VI is still running, you can:

• Use the Wait on Asynchronous Call function in a parallel operation to your main code.
• When the Wait on Asynchronous Call function returns, set a Boolean flag to True. This can be achieved through a Functional Global Variable (FGV).
• You main code can continuously read the Boolean flag in the FGV to determine when the Wait on Asynchronous Call function has returned without blocking your code execution.

The Execution:State property gives the current state of a VI. Querying this will only work if the VI is opened as a non-typed reference (when the type specifier VI Refnum input is unwired).

Additional Information