I would like to setup 3 digital ports on PXI - 6512 card using Daqmx write function. what is the best option I can choose for writting? If I choose to write as "single channel single input U32" would it work. The question I have is U32 has 32 bits where as 3 ports contains only 24 lines.
Your initial question appears to indicate that you want to write to "output" ports, but the vi you reference is an "input" one. As to using a U32 when you only have 24 output pins, only the lower 24 bits would be used, so you should be ok.
Putnam Certified LabVIEW Developer
Senior Test Engineer North Shore Technology, Inc. Currently using LV 2012-LabVIEW 2018, RT8.5