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Chapter 3 Hardware
44 Reference Manual LittleBoard 550
Table 3-14. Serial A Interface Pin/Signal Descriptions (J11)
Pin # Pin #
DB9
Signal Description
11
(COM1)
DCD1* Data Carrier Detect 1 – 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 DTR1
as part of the DTR/DSR handshake.
2 6 DSR1* Data Set Ready 1 – Indicates external serial communications device is
powered, initialized, and ready. Used as hardware handshake with DTR1
for overall readiness to communicate.
32RXD1
RX1-
Receive Data 1 – Serial port 1 receive data in.
RX1- – If in RS485 or RS422 mode, this pin is Receive Data 1 -.
47RTS1*
TX1+
Request To Send 1 – Indicates Serial port 1 is ready to transmit data.
Used as hardware handshake with CTS1 for low level flow control..
TX1+ – If in RS485 or RS422 mode, this pin is Transmit Data 1 +.
53TXD1
TX1-
Transmit Data 1 – Serial port 1 transmit data out.
TX1- – If in RS485 or RS422 mode, this pin is Transmit Data 1 -.
68CTS1*
RX1+
Clear To Send 1 – Indicates external serial communications device is
ready to receive data. Used as hardware handshake with RTS1 for low
level flow control.
RX1+ – If in RS485 or RS422 mode, this pin is Receive Data 1 -.
74DTR1*
Data Terminal Ready 1 – Indicates Serial port 1 is powered, initialized,
and ready. Used as hardware handshake with DSR1 for overall readiness
to communicate.
89RI1*
Ring Indicator 1 – Indicates external serial communications device is
detecting a ring condition. Used by software to initiate operations to
answer and open the communications channel.
9 5 GND Ground
10 NC KEY/
NC
Key
Not connected
11 1
(COM2)
DCD2* Data Carrier Detect 2 – 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 DTR2
as part of the DTR/DSR handshake.
12 6 DSR2* Data Set Ready 2 – Indicates external serial communications device is
powered, initialized, and ready. Used as hardware handshake with DTR2
for overall readiness to communicate.
13 2 RXD2
RX2-
Receive Data 2 – Serial port 2 receive data in
RX1- – If in RS485 or RS422 mode, this pin is Receive Data 2 -.
14 7 RTS2*
TX2+
Request To Send 2 – Indicates Serial port 2 is ready to transmit data.
Used as hardware handshake with CTS2 for low level flow control.
TX2+ – If in RS485 or RS422 mode, this pin is Transmit Data 2 +.
15 3 TXD2
TX2-
Transmit Data 2 – Serial port 2 transmit data out
TX2- – If in RS485 or RS422 mode, this pin is Transmit Data 2 -.