RS900 Family Installation Guide
4 Serial Ports
Serial ports can be either DB9 Serial ports, RJ45 serial ports or Fiber Serial ports

4.1 DB9 Serial Port

The DB9 port is selectable via software to be RS232, RS485 or RS422.
Figure 15: DB9 Female DCE Port pin-out
Pin RS232 Mode RS485 Mode RS422 Mode
1 DCD - -
2 TX TX/RX+ TX+
3 RX - RX+
4 DTR - -
5 Common (Isolated Ground)
6 DSR - RX-
7 CTS TX/RX - TX-
8 RTS - -
9 RI (No Connection) - -
Shield Chassis Ground
Table 9: DB9 Female DCE Port pin-out
NOTES:
1. No internal termination is provided.
2. Pins 1, 4, and 6 are connected internally. Pins 7 and 8 are connected internally. The pins are
permanently asserted to 5V so that DTE devices that require DCD, DTR, or CTS signals will
operate. However, hardware flow control via RTS is not recognized.
3. The Common terminals are optically isolated; however, there is transient voltage protection
circuitry between the Common terminals and chassis ground.
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