Getting Started
[Documentation number: 2000430 Rev B] 7
Data-Only Null-Modem Cables
Data-Only Null-
Modem Cables
If no hardware flow is required, use the pinouts in the following figure. If you are
using a 3-wire cable and you need control, use software flow control.
Control Loopback
Cables
Some equipment may not require hardware handshaking. However, they may
require that certain control signals are active before sending data.
RS-422 to DTE
Cables
Most RS-422 communication links do not use hardware handshaking or signal ground lines.
The following figure shows twisted-pair transmission lines.
Shielded vs. Unshielded
If the Comtrol device falls within the limits for a Class A computing device
established by the FCC, the serial cables used to connect the Comtrol device to the
external devices must be shielded. The cable shield must connected to the chassis
ground at both ends to reduce EMI. If the cable shield is not connected to the
chassis ground at both ends, the EMI radiation from your system may exceed the
limits allowed for FCC class A equipment. You can use an isolation device if you
experience problems with ground loops.
Refer to the statement on electromagnetic compliance in the Comtrol hardware
document to determine the FCC class for your Comtrol product.
RocketPort Connector
Signal
TxD
RxD
GND
Name
DB25
2
3
7
Signal
RxD
TxD
GND
Name
Pins
DB9
2
3
5
Pins
DB25
3
2
7
Pins
Customer DTE Connector
RJ45
4
5
3
Pins
RJ11 DB9
3 3
4 2
2 5
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
RTS
CTS
DSR
GND
DCD
DTR
Name
Pins
DB9
2
3
7
8
6
5
1
4
Pins
DB25
3
2
4
5
6
7
8
20
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
RocketPort Connector
TxD+
RxD+
Name
DB25
19
15
Signal
RxD+
TxD+
Name
Pins
Customer DTE
TxD-
25
RxD-
17
Signal
RxD-
TxD-
GND 7 GND
Connector
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