Connecting Serial Devices; Dte Versus Dce; Db9 Serial Cables And Loopback Plugs - Comtrol RocketPort INFINITY User Manual

DTE Versus DCE

DB9 Serial Cables and Loopback Plugs

RocketPort INFINITY User Guide: 2000465 Rev. G

Connecting Serial Devices

This section provides information about the RocketPort INFINITY connectors, in
the event that you need to build cables or loopback plugs.
• DB9 Serial Cables and Loopback Plugs
• DB25 Serial Cables and Loopback Plugs
• RJ45 Serial Cables and Loopback Plugs
• RJ11 Serial Cables and Loopback Plugs
A loopback plug is a serial port plug with pins wired together that you can use
with an application (for example, the diagnostic, Test Terminal, or minicom) to
test serial ports. See Before Calling Technical Support
about using the test application shipped with the RocketPort INFINITY.
Most devices, except modems, are Data Terminal Equipment (DTE) devices.
Modems are Data Communication Equipment (DCE) devices. RocketPort
INFINITY ports are configured as DTE.
How you build a cable depends on which device your are connecting to (DTE or
DCE). For example, you need a null-modem cable to connect the COM ports
(COM1 or COM2) on the computer or the RocketPort INFINITY ports to printers,
terminals, bar code readers or DNC equipment. If you are connecting a DTE
device to a DCE device you need a straight-through modem cable.
• Straight-through cable (DTE to DCE) - connects TxD to TxD and RxD to RxD.
• Null-modem cable (DTE to DTE) - connects TxD to RxD and RxD to TxD.
The following figures and table illustrate the signals present on DB9 connectors if
you need to build your own null-modem or straight-through DB9 serial cables.
Quadcable, octacable, and the interface boxes use DB9 male connectors.
• DB9 Signals on Page 12
• DB9 Null-Modem Cables (RS-232)
• DB9 Null-Modem Cables (RS-422 or RS-485 Full-Duplex)
• DB9 Straight-Through Cables (RS-232 or RS-485 Half-Duplex)
• DB9 Loopback Plugs
on Page 11
on Page 14
on Page 17
on Page 19
on Page 12
on Page 13
on Page 25 for information
on Page 12
on Page 13
Connecting Serial Devices - 11