CME34M Hardware Manual - RTD Embedded Technologies, Inc.

Serial Port 1 (CN7) and Serial Port 2 (CN8)
Serial Port 1 (COM1) is implemented on connector CN7, and Serial Port 2 is implemented on connector CN8.
The serial ports are normally configured as PC compatible full-duplex RS-232 ports, but you may use the BIOS
Setup program to reconfigure these ports as half-duplex RS-422 or full-duplex RS-422 or RS-485. If you
reconfigure the ports, you must also select the I/O address and corresponding interrupt using Setup. Table 13
provides the standard I/O addresses and corresponding interrupts.
Table 13
Serial Port Settings
I/O Address (hex)
03F8
02F8
03E8
02E8
IRQ
IRQ4
IRQ3
IRQ4
IRQ3
Serial Port UART
The serial ports are implemented with a 16550-compatible UART (Universal Asynchronous Receiver/
Transmitter). This UART is capable of baud rates up to 115.2 kbaud in 16450 and 16550A compatible mode, and
includes a 16-byte FIFO. Refer to any standard PC-AT hardware reference for the register map of the UART. For
more information about programming UARTs, refer to Appendix D.
RS-232 Serial Port (Default)
The default serial port mode is full-duplex RS-232. With this mode enabled, the serial port connectors must be
connected to RS-232 compatible devices. Table 14 provides the serial port connector pinout and shows how to
connect to an external DB-25 or DB-9 compatible serial connector.
Table 14
Serial Port in RS-232 Mode
Pin Signal Function In/Out DB-25 DB-9
1 DCD Data Carrier Detect in 8 1
2 DSR Data Set Ready in 6 6
3 RXD Receive Data in 3 2
4 RTS Request To Send out 4 7
5 TXD Transmit Data out 2 3
6 CTS Clear To Send in 5 8
7 DTR Data Terminal Ready out 20 4
8 RI Ring Indicate in 22 9
9,10 GND Signal Ground — 7 5
32 CME34M cpuModule BDM-610000076 Rev A