I have to get to the office and see if I have that schematic. I should.
The original software was designed that the 2 axis did not have DNC capability. The 3 axis did. At version 5, the same disk was used to load both 2 and 3 axis so I believe that both styles should DNC. You would have to read the manual though because my memory is of these doing DNC from the floppy or DOM (disk on a module). I believe the serial port was for program transfer and not for DNC.
George
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)