Following repeated failure to establish communication between c1vac and the XGS600 controller via Perle IOLAN serial device server, I decided to monitor the signal voltage of the communication channels (pin#2, pin#3 and pin#5) using an oscilloscope. The result of this investigation is presented in the attached pdf document. In summary, it seems I have used a crossed wired RS232 serial cable instead of a normal RS232 serial cable, so the c1vac read request command is being relayed on the wrong comm channel (pin#2 instead of pin#3). I will swap out the cable to see if this resolves the problem.