Good day,
I am writing a test executive where it needs to scan the bus for support of older (HP/Agilent 856x series) and newer (Agilent 440x and 444x series) spectrum analyzers. *NOTE* I originally posted this question in my NI Community blog. I apologize for redundancy but someone recommended I re-post here.
The first frame looks for the newer analyzers with *IDN? then if that fails sets the boolean in the error cluster to TRUE. The next frame then uses the error cluster's boolean to decide whether an older HP analzer is connected instead using ID? query. Disclaimer: the second frame is a clone of the ID query of the 856x Initialize VI. I just want to use what already worked - no reinventing the same wheel? 
But, lo and behold, it doesn't work as expected. If I have the frames in this order and connect a HP8563E the GPIB time's out error. This code works with the newer 4407 or 4440 since the *IDN? query passes and the second frame is not executed.
Now, when I move the second frame to become the first frame and run it with HP8563E the query works but will have a GPIB timeout if I have the 4407 or 4440 connected.
Long story short, how do I support both older GPIB ID? and newer IDN? in my code?
I have attached the query VI created with LV 2012.
Many thanks!
Aldrin