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Chapter 3
Table 3-14. Serial A Interface Pin/Signal Descriptions (J11)
Pin # Pin #
DB9
1
1
(COM1)
2
6
3
2
4
7
5
3
6
8
7
4
8
9
9
5
10
NC
11
1
(COM2)
12
6
13
2
LittleBoard 700
Signal
Description
DCD1* Data Carrier Detect 1 – Indicator to serial port 1 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 DTR1
as part of the DTR/DSR handshake. Designed for direct input from
external RS232 receiver.
DSR1*
Data Set Ready 1 – Indicator to serial port 1 that external serial
communications device is powered, initialized, and ready. Used as
hardware handshake with DTR1 for overall readiness to communicate.
Designed for direct input from external RS232 receiver.
RXD1
Receive Data 1 – Serial port 1 receive data in.
RX1-
RX1- – If in RS485 or RS422 mode, this pin is Receive Data 1 -.
RTS1*
Request To Send 1 – Indicator to serial output port 1 is ready to transmit
data. Used as hardware handshake with CTS1 for low level flow control.
TX1+
TX1+ – If in RS485 or RS422 mode, this pin is Transmit Data 1 +.
TXD1
Transmit Data 1 – Serial port 1 transmit data out.
TX1-
TX1- – If in RS485 or RS422 mode, this pin is Transmit Data 1 -.
CTS1*
Request To Send 1 – Indicator to serial output port 1 is ready to transmit
data. Used as hardware handshake with CTS1 for low level flow control.
RX1+
RX1+ – If in RS485 or RS422 mode, this pin is Receive Data 1 -.
DTR1*
Data Terminal Ready 1 – Serial port 1 indicator that port is powered,
initialized, and ready. Used as hardware handshake with DSR1 for
overall readiness to communicate. Designed for direct input to external
RS232 driver.
RI1*
Ring Indicator 1 – Indicator to serial port 1 that external modem is
detecting a ring condition. Used by software to initiate operations to
answer and open the communications channel. Designed for direct input
from external RS232 receiver (whose input is typically not connected in
direct connect environments)
GND
Digital Ground
KEY/
Key
NC
Not connected
DCD2* Data Carrier Detect 2 – Indicator to serial port 2 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 DTR1
as part of the DTR/DSR handshake.
DSR2*
Data Set Ready 2 – Indicator to serial port 2 that external serial
communications device is powered, initialized, and ready. Used as
hardware handshake with DTR1 for overall readiness to communicate.
RXD2
Receive Data 2 – Serial port 2 receive data in
RX2-
RX1- – If in RS485 or RS422 mode, this pin is Receive Data 1 -.
Reference Manual
Hardware
41
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