3.4.2. Serial Ports
A pair of asynchronous serial ports may be present on the router.
Figure 4. Serial ports
Serial port 1 operates in RS-232 mode. Serial port 2 is configurable to operate in either RS-232 or RS-485 mode.
The pin numbering of the serial port connector, when viewed from the front of the unit, is shown below.
1
8
Figure 5. Pin numbering of serial port
RS-232 ports
When you configure a serial port to operate as an RS-232 interface, it supports the following signals:
• Transmit Data
• Receive Data
• CTS
• RTS
• DSR
• DTR
The pin numbering of the RJ45 socket, when viewed from the front of the unit, is as shown below. The RS-232
interface is wired as a DCE and the pinout is shown below.
Illustration
Pin no.
Signal
Direction
Description
1
8
1
DSR
Out
Data Set Ready
2
DCD
Out
Data Carrier Detect
3
DTR
In
Data Terminal Ready
4
SG
-
Signal Ground, not chassis ground
5
RD
Out
Receive Data
6
TD
In
Transmit Data
7
CTS
Out
Clear To Send
8
RTS
In
Request To Send
Table 4. RS-232 connection
RS-485 ports
When you configure a serial port to operate as an RS-485 interface, it supports both two-wire (half-duplex) and
four-wire (full-duplex) modes. Configuration between two-wire and four-wire RS-485 modes is under software
control. The pin-numbering of the RJ45 connector in RS-485 mode, when viewed from the front of the unit, is
shown below.
Merlin 4400 Series
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