just cable nothing in between
PLC5/11use channel 0 connected to 1761-net-eni by one cable ( d-sub 25 pin connector to d-sub 9pin to eni)
on plc chan 0 configure as rs232 system point to point, baud rate 9600, bit per char 8, stop bit 1, parity none, error detect crc, and control line no hand shaking
chan 1A--data highway plus