Specifications

Chapter 3 Hardware
24 Reference Manual LittleBoard 735
Note: The shaded area denotes power or ground. Signals are listed in the table with RS232 first, followed
by RS422/RS485. The signals marked with * = Negative true logic.
16 8 CTS2*
RX2+
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+ – If in RS485 or RS422 mode, this pin is Receive Data 2 -.
17 4 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.
18 9 RI2* Ring Indicator 2 – Indicates external serial communications device is
detecting a ring condition. Used by software to initiate operations to
answer and open the communications channel.
19 5
GND Ground
20 NC NC Not connected
Table 3-6. Serial B Interface Pin Signals (J12)
Pin # Pin #
DB9
Signal Description
11
(COM3)
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.
2 6 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.
32RXD3
RX3-
Receive Data 3 – Serial port 3 receive data in
RX3- – If in RS485 or RS422 mode, this pin is Receive Data 3 -.
47RTS3*
TX3+
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 +.
5 3 TXD3
TX3-
Transmit Data 3 – Serial port 3 transmit data out
TX3- – If in RS485 or RS422 mode, this pin is Transmit Data 3 -.
68CTS3*
RX3+
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+ – If in RS485 or RS422 mode, this pin is Receive Data 3 -.
7 4 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.
8 9 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.
95
GND Ground
10 NC KEY Not Connected
Table 3-5. Serial A Interface Pin Signals (J11) (Continued)