Serial Port Pin-Out Diagram
Pin
RS-232
RS-422/485
1
NC
RX+
2
RX
3
TX
4
DTR
TX-
5
GND
GND
6
DSR
7
RTS
TX+
8
CTS
9
NC
RX-
LED Indicators for Serial Ports 1 & 2
There are two (2) sets of LEDs, one set for each serial port. Each set consists of two (2) red LEDs that
indicate activity on the pins.
When using RS-232 communications, the two LEDs indicate activity on the TX and RX pins.
When using RS-422/485 communications, the LEDs indicate activity on the corresponding TX+, TX-,
RX+, and RX- pins.
RS-422 Operation:
When using RS-422 operation the RX+ and RX- should have a 120 Ohm resistor across the two pins.
Also, RS-422 operation must be selected in the setup page in order for it to properly work.
RS-485 Operation:
When using the RS-485 operation the RX+ and TX+ should be tied together as well as the RX- and TX-.
There should be a 120 Ohm termination resistor across the two pins. Also, RS-485 operation must be
selected in the setup page in order for it to properly work.