Specifications

Chapter 4 Hardware Reference
38 Users Guide ReadyBox
Serial Interface
The ReadyBox supports 4 serial ports, Serial 1 (COM1), Serial 2 (COM2), Serial 3 (COM3), and Serial
4 (COM4). The ReadyBoard provides two of four standard D-shell 9-pin (DB9) connectors on the board
for Serial 1 (COM1) and Serial 2, (COM2). The ReadyBox provides the other two standard DB9
connectors for Serial 3 (COM3) and Serial 4 (COM4) with cables connecting at the ReadyBoard Serial B
header for Serial 3 (COM3) and Serial 4 (COM4) ports.
• The ReadyBox supports two of the four standard D-shell 9-pin (DB9) connectors
♦ Serial Port 3 (COM3) supports RS232/RS485/RS422
♦ Serial Port 4 (COM4) supports RS232/RS485/RS422
Refer to the specific ReadyBoard Reference Manual for more information
NOTE The RS232 and RS485/RS422 modes must be selected in the ReadyBoard
BIOS Setup Utility. Generally, the RS232 mode is the default selection
(Standard) for any serial port.
To implement the RS485 mode on Serial port 3 or 4 (COM3 or COM4), you must tie the correct pins
together for each port. For example; on Serial port 3, tie pin 2 (RX3-) to 3 (TX3-) and pin 7 (TX3+) to 8
(RX3+) at the DB9 serial connector for Serial port 3 or 4 as shown in Figure 3-1. The RS422 mode uses
a four-wire interface and does not need any pins tied together, but you must select RS485 in BIOS Setup.
54321
9876
Standard DB9 Serial
Port Connector (Female)
Rear View
RdyBxRS485Con
Figure 4-1. RS485 Serial Port Implementation
Tables 4-3 and 4-4 give the pins and corresponding signals for Serial Ports 3 (COM3) and 4 (COM4).
Table 4-3. Serial 3 Port Connector Pin/Signal Descriptions
Pin # Signal Description
1 DCD3 Data Carrier Detect 3 – 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.
2RX3
RX3-
Receive Data 3 – Serial port 3 receive data in
RX3- – If in RS485 or RS422 mode, this pin is Receive Data 3 -.
3TX3
TX3-
Transmit Data 3 – Serial port 3 transmit data out
TX3- – If in RS485 or RS422 mode, this pin is Transmit Data 3 -.
4 DTR3 Data Terminal Ready 3 – Serial port 1 indicator that port is powered,
initialized, and ready. Used as hardware handshake with DSR1 for overall
readiness to communicate.
5 GND Ground
6DSR3
Data Set Ready 3 – Indicator to serial port 1 that external serial
communications device is powered, initialized, and ready. Used as hardware
handshake with DTR3 for overall readiness to communicate.