Comtrol Cable - Manual (Page 6)

6 [Documentation number: 2000430 Rev B] Getting Started
DTE versus DCE
DTE versus DCE
Most devices, except modems, are Data Terminal Equipment (DTE) devices.
Modems are Data Communication Equipment (DCE) devices. Comtrol 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 DeviceMaster 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) - Connect TxD to RxD and RxD to TxD.
RS-232 DTE to DCE This topic describes how to build a straight-through cable. Use a straight-through
cable to connect to a DCE device.
Straight-Through
Cables The following figure shows the most common types of DTE to DCE cables. This
cable configuration works with most modems and is generally called a modem
cable.
Note: If you have a DTE to DCE interface but are uncertain as to which signals
are required, you can use a full 25-wire cable. The 25-wire cable is
constructed as shown in the following cable example, but the remaining
pins are not used.
RS-232 DTE to DTE This topic describes how to build a null-modem cable for connecting to a DTE
device.
Null-Modem Cables If you need RTS-CTS/DTR-DSR hardware flow control, you can use the pinouts
provided in the following example.
Note: If the wiring on the peripheral device differs from the one shown below,
adjust the pinouts accordingly. Refer to the manufacturer’s installation
document if you need help with connector pinouts or cabling for the
peripheral device.
RocketPort Connector
Signal
TxD
RxD
RTS
CTS
DSR
GND
DCD
DTR
Name
DB25
2
3
4
5
6
7
8
20
Signal
TxD
RxD
RTS
CTS
DSR
GND
DCD
DTR
Name Pins
DB9
3
2
7
8
6
5
1
4
Pins
DB25
2
3
4
5
6
7
8
20
Pins
Customer DCE Connector
RJ45
4
5
1
8
7
3
6
2
Pins
RJ11 DB9
3 3
4 2
N/A 7
N/A 8
N/A 6
2 5
5 1
1 4
Pins Pins
RocketPort Connector
Signal
TxD
RxD
RTS
CTS
DSR
GND
DCD
DTR
Name
DB25
2
3
4
5
6
7
8
20
Signal
RxD
TxD
CTS
RTS
DTR
GND
DCD
DSR
Name Pins
DB9
2
3
8
7
4
5
1
6
Pins
DB25
3
2
5
4
20
7
8
6
Pins
Customer DTE Connector
RJ45
4
5
1
8
7
3
6
2
Pins
RJ11 DB9
3 3
4 2
N/A 7
N/A 8
N/A 6
2 5
5 1
1 4
Pins Pins