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Chapter 3
Pin # Pin #
DB9
11
1
(COM4)
12
6
13
2
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 table with RS232 first,
followed by RS485/RS422.
44
Signal
Description
DCD4* Data Carrier Detect 4 – Indicates external serial communications device
is detecting a carrier signal (i.e., a communication channel is currently
open). In direct connect environments, this input will be driven by DTR4
as part of the DTR/DSR handshake.
DSR4*
Data Set Ready 4 – Indicates external serial communications device is
powered, initialized, and ready. Used as hardware handshake with DTR4
for overall readiness to communicate.
RXD4
Receive Data 4 – Serial port 4 receive data in
RX4-
RX4- – If in RS485 or RS422 mode, this pin is Receive Data 4 -.
RTS4*
Request To Send 4 – Indicator to serial output port 4 is ready to transmit
data. Used as hardware handshake with CTS4 for low level flow control.
TX4+
TX4+ – If in RS485 or RS422 mode, this pin is Transmit Data 4 +.
TXD4
Transmit Data 4 – Serial port 4 transmit data out
TX4-
TX4- – If in RS485 or RS422 mode, this pin is Transmit Data 4 -.
CTS4*
Clear To Send 4 – Indicator to serial port 4 that external serial
communications device is ready to receive data. Used as hardware
handshake with RTS4 for low level flow control.
RX4+
RX4+ – If in RS485 or RS422 mode, this pin is Receive Data 4 +.
DTR4* Data Terminal Ready 4 – Indicates this Serial port is powered, initialized,
and ready. Used as hardware handshake with DSR4 for overall readiness
to communicate.
NC
Not connected (Ring Indicator 4)
GND
Ground
NC
Not connected
Reference Manual
Hardware
LittleBoard 800
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