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40 - Connecting Serial Devices DeviceMaster PNIO | UP User Guide : 2000639 Rev. A
Connecting Serial Devices
DB9 Loopback Plugs Loopback connectors are DB9 female serial port plugs with pins wired together
that are used in conjunction with application software to test serial ports. The
DeviceMaster UP is shipped with a a single loopback plug (RS-232/422).
Wire the following pins together to build additional plugs or replace a missing RS-
232 loopback plug:
• Pins 1 to 4 to 6
• Pins 2 to 3
• Pins 7 to 8 to 9
Wire the following pins together for an RS-422 loopback plug:
• Pins 2 to 3
• Pins 7 to 8
Connecting DB9
Serial Devices You can use this information to connect serial devices to DB9 connectors.
1. Connect your serial devices to the appropriate serial port on the DeviceMaster
UP using the appropriate cable.
Note: Refer to the hardware manufacturer’s installation documentation if you
need help with connector pinouts or cabling for the peripheral device.
2. DeviceMaster UP 4-port: verify that the devices are communicating properly.
Note: DeviceMaster UP 1-port, 2-port models,
and the 4-port DIN models do not have
TX/RX LEDs.
The RX (yellow) and TX (green) LEDs function
accordingly when the cable is attached properly to a serial device.
• After power cycling the DeviceMaster UP (appropriate models), the RX/TX
LEDs are off.
• The LEDs do not function as described until the port has been opened by
an application.
3. You can refer to Network and Device LEDs on Page 159 for information about
the remaining LEDs.
Pin 1
Pin 5
Pin 6
Pin 9
RS-232 Only
(Back View)
The RS-232 loopback plug
also works for RS-422.
Pin 1
Pin 5
Pin 6
Pin 9
RS-422 Only
(Back View)