Comtrol RocketPort 485 Series, Hardware Installation Card, Page: 4 / 8

RocketPort® 485 Hardware Installation Card 4 of 8
• Interface box
DB25 Interfaces
Use the following subsections for DB25 interface
connectors. The Quad- and Octacable DB25 fanouts use
DB25 male connectors.
Note: Although the RocketPort 485 card supports eight
ports, if you have a quadcable connected, you will
only have four ports available for use.
DB25 Pinouts
The following table and figure illustrates the DB25
connectors:
Depending on jumper configuration, the pins carry the
following values:
* Ports 1 and 2 can be either RS-232 or RS-485, while
Ports 3 through 8 are RS-232 only. All RS-232 modem
control signals are present in RS-485 mode, but not
used.
** Ports 3 - 8 can be configured to carry +5V on Pin 22.
Do not use the +5V power option with the Quad/
Octacable. Using this feature with interfaces
other than the DB9 box may result in
unacceptable voltage loss.
Building DB25 Female Loopback Plugs or Cables
To perform loopback
testing of DB25 ports in
RS-232 mode, obtain or
create a female DB25
connector with the
following pins wired
together:
• Pins 2 to 3
• Pins 4 to 5 to 22
• Pins 6 to 8 to 20
Note: (The connector illustrated is the standard DB25F
supplied by Comtrol for use with RS-232/422
interfaces.)
To test DB25 ports in RS-485 mode, obtain two female
DB25 connectors and create the cable shown below:
Pin RS-232 Signal RS-485 Signal
1 Not used Not used
2 TxD TRX+
3 RxD TRX-
4 RTS Not used*
5 CTS Not used*
6 DSR Not used*
7 Signal ground Signal ground
8 DCD Not used*
9-19 Not used Not used
20 DTR Not used*
21 Not used Not used
22 ** **
23-25 Not used Not used
Pin 14 Pin 25
Pin 1 Pin 13
Caution
Pin 13 Pin 1
RS-232 Only (Back View)
Pin 25 Pin 14
Pin 13 Pin 1
Pin 14 Pin 25
RS-485 (Back View)
Pin 13 Pin 1
Pin 14 Pin 25
Pin 2 (TRX+)
Pin 3 (TRX-)