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Chapter 3
Pin # Pin #
DB9
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.
Table 3-15. Serial B Interface Pin/Signal Descriptions (J12)
Pin # Pin #
DB9
1
1
(COM3)
2
6
3
2
4
7
5
3
6
8
7
4
8
9
9
5
10
NC
LittleBoard 800
Signal
Description
CTS2*
Clear To Send 2 – Indicates 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 – Indicates Serial port 1 is powered, initialized,
and ready. Used as hardware handshake with DSR2 for overall readiness
to communicate.
NC
Not Connected (Ring Indicator 2)
GND
Ground
NC
Not connected
Signal
Description
DCD3* Data Carrier Detect 3 – 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 DTR3
as part of the DTR/DSR handshake.
DSR3*
Data Set Ready 3 – Indicates external serial communications device is
powered, initialized, and ready. Used as hardware handshake with DTR3
for overall readiness to communicate.
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 – Indicates Serial port 3 is ready to transmit data.
Used as hardware handshake with CTS3 for low level flow control.
TX3+ – If in RS485 or RS422 mode, this pin is Transmit Data 3 +.
TX3+
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 – Indicates 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 -.
DTR3* Data Terminal Ready 3 – Indicates this Serial port is powered, initialized,
and ready. Used as hardware handshake with DSR3 for overall readiness
to communicate.
RI3*
Ring Indicator 3 – Indicates external serial communications device is
detecting a ring condition. Used by software to initiate operations to
answer and open the communications channel.
GND
Ground
KEY
Not Connected
Reference Manual
Hardware
43
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