What ACR Global Variables should I use in HMI Applications?

For HMI applications that use binary data transfers, like our Powerstation and Interact products, it is best to use 32-bit data types. 

All binary transfers to and from the ACR controllers are 32-bit transfers.  Avoid using the 64-bit floating point variables (P0 through P4095) as their accuracy is not guaranteed when tranferred via 32-bit transfers.  It is better to use the global 32-bit integer and float user variables (P38912-P39423) that are outlined in our "User Variables" section of the DirectVARS application note.

http://divapps.parker.com/divapps/emn/download/SupportSamples/ACR96xx/AN_DirectVARS.pdf

Alternately, it is possible to scale the floating point numbers on each end of the transfer such that they will be integer numbers when transferred.  This will ensure translation errors do not occurs.