rtd cpuModules CME34BT, User Manual, Page: 46 / 110

38 CME34BT cpuModule BDM-610000088 Rev A
Serial Port 1 (CN7) and Serial Port 2 (CN8)
Serial Port 1 (COM1) is implemented on connector CN7 , and Serial Port 2 (COM2) 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 11 provides the standard I/O addresses and corresponding interrupts.
Serial Port UART
The serial ports are implemented with a 16550/16750-compatible UART (Universal Asynchronous
Receiver/ Transmitter). This UART is capable of baud rates up to 115.2 kbaud, and includes a 64-byte FIFO.
Refer to any standard PC-AT hardware reference for the register map of the UART.
It is possible to change the slew rate for the UARTs of the cpuModule to allow the serial ports to operate at
higher speeds than 115200 bps. For more information see Chapter 4 - “Non-Standard Serial Port Modes” .
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 12 provides the serial port connector pinout and shows
how to connect to an external DB-25 or DB-9 compatible serial connector.
Table 11 Serial Port Settings
I/O Address (hex) IRQ
03F8 IRQ4
02F8 IRQ3
03E8 IRQ4
02E8 IRQ3
Table 12 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 GND Signal Ground — 7 5
10 GND Signal Ground — — —