You can use the VISA Write to output data to one serial port and like
Mads suggested, have a loopback cable to another serial port to do a
read from. The actual format of the data is what might get tricky.
There is no kind of standard describing what the data from a serial
instrument should look like but if you have that information from the
manufacturer you can probably be able to code up a simple simulator.
It's doing the full functionality of the instrument in sofware that
will be the real time sink.
