Any Suggestion for communication between three 90-70 GMR PLCs (15 - pin. RS-485 programming port) to SCADA PC . PC is not having serial port.
Distance between PLCs and PC is around 150 Meter.
I suggest that you get an RS-485 to USB adapter for your PC and connect them per the 90-70 Multi-Drop serial communications directions found in the manual.
For the correct manual for this Communications you should contact CEMTEC who are the current owners of the 90-70 PLC.
Or search the GE Knowledge site.