PCI-COM-2S and PCI-422/485-2

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  • Universal PCI, PCI-X, 3.3V and 5V compatible (Call for PCI-Express availability)
  • Dual-port serial communications card for PCI bus
  • Supports RS-232(PCI-COM2S only), RS-422, and RS-485 protocols
  • Automatic control of RS-485 driver under Windows systems
  • Includes type 16550 UART with 16-byte FIFO buffers
  • Baud rates up to 460,800 baud
  • Detected as standard COM ports under Windows 95/98/98se/NT4/NT2000/XP -> 10, both 32 & 64 bit etc
  • No base address or IRQ switches to set
  • Support for Wind River VxWorks (call for ordering information)
  • Designed, made, supported, and manufactured in the USA
Last updated on November 2, 2023, 6:26 pm


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PCI Dual-Port Serial Interface Cards

The PCI-COM2S and PCI-422/485-2 are dual-port, asynchronous serial communications cards designed for use in PCI-Bus computers. They are 6.5 inches (165 mm) long and may be installed in any 3.3V or 5V PCI or PCI-X slot. Each independent port supports RS-422 and RS-485 balanced-mode transmission/reception, and on the PCI-COM2S, RS-232 single-ended transmission/reception as well. Each port of the PCI-COM2S and PCI-422/485-2 has the capability to add bias voltage. (RS-485 communication requires that one transmitter in the network must supply a bias voltage to ensure a known “zero” state when all transmitters are OFF). Also, receiver inputs at each end of the network should be terminated to eliminate ringing. The PCI-COM2S and PCI-422/485-2 support these options by means of jumpers on the card.
Type 16550 UARTs are used as the asynchronous communication elements. These include a 16-byte transmit/receive FIFO buffer to protect against lost data in multitasking systems while maintaining 100 percent compatibility with the original IBM serial port. A crystal oscillator is located on the card and permits precise baud rate capability up to 115,200. Higher baud rates, up to 460,800 baud, are achieved by changing a jumper on the card. The driver/receivers used, type 75ALS180, are capable of driving extremely long communication lines at high baud rates. They can drive up to ±60 mA on balanced lines and receive inputs as low as 200 mV differential signal superimposed on common mode noise of +12V to -7V. In case of communication conflict, the driver/receivers feature thermal shutdown.

When the card is first installed your operating system should automatically detect and configure the two COM ports for immediate use.


In RS-485 communications the driver must be enabled when needed and then disabled to permit all cards on the network to share a two-wire or four-wire cable. The PCI-COM2S and PCI-422/485-2 cards have two methods to control the driver: automatic (AUTO) and request-to-send (RTS) control. Under automatic control, the driver is enabled (and the receiver disabled) when data are ready to be transmitted. When transmission is complete, the driver remains enabled for the transmission time of one additional character and then is disabled. The card automatically adjusts its timing to the baud rate of the data. (NOTE: For use in half-duplex mode under Windows, PCI-COM2S must be operated in the AUTO mode.) In the RTS mode, application software must set a bit to enable the driver and reset that bit to disable the driver.




Drivers and Downloads

Full list of available Downloads: Software Packages, Drivers, Manuals, and other documents

Information about our Free Software packages:

ACCES is proud to provide a full suite of software support with every Data Acquisition product. We are committed to supporting the most popular operating systems and platforms for our customers. Currently we are actively supporting XP -> 10, both 32 & 64 bit, including “Server 2008,” “Embedded,” and “Compact” flavors for all plug-and-play products including PCI, PCI Express, USB, and more. Many products continue to ship with support for additional operating systems such as DOS, Windows 95, 98, Me, NT4, and 2000.


Among the software we deliver with our products are sample programs in a wide variety of programming languages. These samples are used to demonstrate the software interfaces to our products — and many can be used as-is in your production environments, or to test functionality of the devices out-of-the-box. We’re currently actively supporting sample programs in Microsoft Visual C#, Visual Basic, Delphi, and Visual C/C++, with many devices including samples in Borland C/C++ 3.1 for DOS. Additionally we provide National Instruments LabVIEW compatible DLLs and many demonstration VIs for our devices.


Drivers for various operating systems are also provided, including active support for Windows XP -> 10 — all in both 32-bit and 64-bit flavors, and including consumer, server, and embedded varieties — as well as the 2.6 and newer Linux kernels and recent OSX / macOS versions. Many products continue to ship with driver support for Windows 95, 98, Me, NT4, and Windows 2000, but support for these operating systems is considered deprecated.

Setup Programs and Utilites

Our Data Acquisition devices also include a graphical setup utility that walks you through the process of configuring any option jumpers or switches on the device, as well as explaining a little about the various connectors present.

Many devices also include utility programs – little tools to make your use of the device easier, such as EWriter, a program that allows you to read and write data in the user-accessible EEPROM locations on all our USB data acquisitition products; or WinRISC, a “Really Incredibly Simple Communications” terminal program that lets you get started instantly with serial devices.

“Register Level” Documentation

Besides all this software in all these languages and operating systems ACCES has a policy of open and transparent development: none of our lowest-level “register” interfaces are hidden from you — we document every register in every bus card, every command in every serial board, and every usb control transfer in every USB Data Acquisition board. These lowest-level interfaces allow you to develop for our products in ANY operating system or language, regardless of our actively supporting it or having a driver for it. We have customers actively developing in ADA, Android, Python, Java, MATLAB, Solaris, and more, just by referring to our complete low-level interface documentation! And we provide the full source code to all of our drivers, regardless of operating system, to give you an even bigger head start in your own development tasks.

No Fees or Royalties

All of this software is provided at no additional charge, and is licensed under any of a variety of flexible — and royalty free — options. Check out our software license explanation if you’d like more information.

Custom Software

ACCES also offers Custom Software Services for our products. Our prices are unbelievably low, often as inexpensive as free! If you need something tweaked to support your needs, or an entire enterprise application developed from scratch, it is definitely worth your time to inquire with us, first.

Further information about available ACCES Software:

Redistributing Windows Drivers
A list of ACCES drivers and the files that compose them under different versions of Windows, so you can easily redistribute ACCES cards and drivers.


ACCES has successfully partnered with Wind River to bring our entire line of PCI and PCI Express Serial Communication cards to VxWorks 7! All ACCES plug-and-play serial cards are now supported with our VxWorks driver, including RS232, RS422, RS485 (2- and 4-wire) and baud rates up to 10Mbps.

Designed as an update to the existing vxbPciNs16550Sio.c driver, we’ve added support for ×8 baud rates, proper handling of the unique register location of the 4th port in the Pericom PI7C9X7954 UART, and configuring the serial protocol from your application software.

With this driver suite all ACCES PCI, PCI Express, PCI Express Mini Card, M.2, PCI-104, PCIe/104, and all related “PCI Style” plug-and-play serial cards will detect and install as standard VxWorks SIO ports.

Communications Interface

  • I/O Connection: 9-pin male D-sub connectors.
  • Serial Ports: Two shielded male D-sub 9-pin IBM AT style connectors compatible with RS-232(PCI-COM2S only), RS-422 and RS-485 specifications.
  • Character length: 5, 6, 7, or 8 bits.
  • Parity: Even, odd or none.
  • Stop Interval: 1, 1.5, or 2 bits.
  • Serial Data Rates: Up to 115,200 baud, Asynchronous, Asynchronous. A faster range of rates, up to 460,800 baud, is achieved by jumper selection on the card. Type 16550 buffered UART.

Caution: The OUT2 bit of the UART must be set low for proper interrupt driven communication. This bit enables or disables the interrupts and the card will not communicate if the bit is pulled high.

RS-232 Drivers(PCI-COM2S Only)

  • Device: 75C185 Quad Line Transceivers
  • Output Voltage: ± 6VDC minimum, current limited to 10 mA.
  • Receiver threshold: 1.5V high, 0.75 low, Maximum input ±30VDC

RS-422/RS-485 Differential Communication Mode

  • Multipoint: Compatible with RS-422 and RS-485 specifications. Up to 32 drivers and receivers allowed on line. Serial communications ACE used is type 16550. Driver/Receivers used are type 75ALS180.
  • Receiver Input Sensitivity: ±200 mV, differential input.
  • Common Mode Rejection: +12V to -7V
  • Transmitter Output Drive Capability: 60 mA, with thermal shutdown.


  • Operating Temperature Range: 0° to +60° C
  • Humidity: 5% to 90%, non-condensing.
  • Storage Temperature Range: -50° to +120° C
  • Power Required: +5VDC at 125 mA typical, -12VDC at 5 mA typical, +12VDC at 5 mA typical, 750 mW total power consumption.
  • Size: 6 1/2″ long (165 mm) by 3 7/8″ (99 mm)

Regulatory Compliance

  • This product is in full compliance with CE requirements.
ModelDescriptionPrice (USD)

PCI Dual Port RS-422/485 Serial Card


PCI Dual port RS-232/422/485 Serial Card