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Chapter 3
Pin # Pin #
DB9
14
7
15
3
16
8
17
4
18
9
19
5
20
NC
Notes: The shaded area denotes power or ground. Signals are listed in the following order RS232 and
RS485/RS422.
Table 3-15. Serial B Interface Pin/Signal Descriptions (J13)
Pin #
Pin #
DB9
1
1
(COM3)
2
6
3
2
4
7
5
3
6
8
42
Signal
Description
RTS2*
Request To Send 2 – Indicator to serial output port 2 is ready to transmit
data. Used as hardware handshake with CTS2 for low level flow control.
TX2+
TX2+ – If in RS485 or RS422 mode, this pin is Transmit Data 2 +.
TXD2
Transmit Data 2 – Serial port 2 transmit data out
TX2-
TX2- – If in RS485 or RS422 mode, this pin is Transmit Data 2 -.
CTS2*
Clear To Send 2 – Indicator to serial port 2 that external serial
communications device is ready to receive data. Used as hardware
handshake with RTS2 for low level flow control.
RX2+
RX2+ – If in RS485 or RS422 mode, this pin is Receive Data 2 -.
DTR2*
Data Terminal Ready 2 – Serial port 2 indicator that port is powered,
initialized, and ready. Used as hardware handshake with DSR2 for
overall readiness to communicate.
NC
Not Connected
GND
Digital Ground
NC
Not connected
Signal
Description
DCD3* Data Carrier Detect 3 – Indicator to serial port 3 that external modem is
detecting a carrier signal (i.e., a communication channel is currently
open). In direct connect environments, this input will be driven by
DTR3 as part of the DTR/DSR handshake. Designed for direct input
from external RS232 receiver.
DSR3*
Data Set Ready 3 – Indicator to serial port 3 that external serial
communications device is powered, initialized, and ready. Used as
hardware handshake with DTR3 for overall readiness to communicate.
Designed for direct input from external RS232 receiver.
RXD3
Receive Data 3 – Serial port 3 receive data in
RX3-
RX3- – If in RS485 or RS422 mode, this pin is Receive Data 3 -.
RTS3*
Request To Send 3 – Indicator to serial output port 3 is ready to transmit
data. Used as hardware handshake with CTS3 for low level flow
control.
TX3+
TX3+ – If in RS485 or RS422 mode, this pin is Transmit Data 3 +.
TXD3
Transmit Data 3 – Serial port 3 transmit data out
TX3-
TX3- – If in RS485 or RS422 mode, this pin is Transmit Data 3 -.
CTS3*
Clear To Send 3 – Indicator to serial port 3 that external serial
communications device is ready to receive data. Used as hardware
handshake with RTS3 for low level flow control.
RX3+
RX3+ – If in RS485 or RS422 mode, this pin is Receive Data 3 -.
Reference Manual
Hardware
LittleBoard 700
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