It uses VISA functions. The inputs are clusters to define the modbus command, starting address, # of registers, and values and booleans to write. The output is a cluster that contains either the values or the booleans read (depending on which function you choose.)
You can't test it because you need a real device on the other end that knows the protocol. The alternative is to use something like the slave demon running on another PC and connect to the two with a null modem serial cable.
