GX3903 Series - 3 Port RS-232 or RS-422or RS-485 Interface cPCI Cards

3 Port RS-232/RS-422/RS-485 Interface

3 Port RS232/422/485, Isolated, DB-9 I/F
  • (3) 16550-based asynchronous communication ports
  • Each port can be configured for RS232, RS422 or RS485 operation
  • 9-pin micro-D subminiature connectors for each port
  • Supports data rates up to 115 K baud
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The GX3903 is a 3-port, cPCI asynchronous communications interface board supporting RS232 and RS422 levels. Optionally, the board can support RS485 signaling. Each port is configured at the time of order for RS232, RS422 or RS485 signaling. The default configuration is RS232. For RS232 mode, each port supports RTS, CTS, TXD, RXD, DCD, DRC, DSR, and RI signaling. The RS422 mode supports TXD, RXD, CTS, and RTS with each line operating differentially with a uni-directional drive.

In RS485 mode, the card supports both 2-wire and 4-wire configurations. In 2-wire mode, a single differential RS-422 pair operates in half-duplex mode. For 4-wire mode, the TXD is driven on an additional RS422 uni-directional output. Control of the Tx/Rx direction is performed via the RTS control signal from the 16550 UART.


The differential RS422 / RX485 ports are terminated with 150 Ω parallel terminations. Alternate terminations can be specified at time of order. Interfacing to the 3 ports is provided via (3) front panel mounted Micro D9 connectors.

Support for each port is provided by a 16550 UART which operates at data rates up to 115 K baud. Mapping of interrupts, INTA/INTB/INTC/INTD from the PCI bus to each UART is done via switches located on the board, supporting both shared and dedicated interrupt requests.


Standard Windows COM drivers can be used with the GX3903.


Automatic Test Equipment (ATE)
Control of computer peripherals
Computer to computer interfacing
Control of industrial equipment




GX3903 3 Port RS232/422/485, DB-9 I/F
GX3903-I 3 Port RS232/422/485, Isolated, DB-9 I/F




Async Communication Channels
Supported Protocols RS232, RS422, RS485
Factory configurable. Default configuration is RS232.
Number of Ports 3
Connector 9-pin, Micro D-subminiature, male
Supported RS232 Signals RTS, CTS, TXD, RXD, DCD, DTR, DSR, RI
Supported RS422 Signals TXD, RXD, CTS, RTS; differential levels, unidirectional drive
Supported RS485 Signals 2-wire mode: TXD / RXD (half duplex), CTS, RTS
4-wire mode: TXD, TXD / RXD (half duplex), CTS, RTS
Differential levels
UART 16550, one per port. Configurable interrupts, shared or dedicated. Configurable via on-board DIP switches
Maximum Baud Rate 115 K
RS433 / RS485 Termination 150 Ω, optional
Operating Temperature +5 °C to +50 °C
Storage Temperature -20 °C to +60 °C
5% to 90% @ +40 °C
Size 3U cPCI
Weight 200 g


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