P104-COM232-8 and 104I-COM232-8


  • High Performance Octal PCI UART
  • 16550 Compatible Register Set
  • Up to 460Kb/s Serial Data Rate
  • Global Interrupt Source Register
  • Data Transfer in Byte, Word, and Double-Word
  • 64-Byte Transmit and Receive FIFOs per each of eight UARTs
  • Transmit and Receive FIFO Level Counters
  • Programmable Trasmit and Receive FIFO Trigger Level
  • RoHS Available. Please contact us for ordering information
  • Designed, made, supported, and manufactured in the USA
Last updated on November 2, 2023, 6:26 pm


In Stock


PC/104-Plus and PCI-104 8-Port RS-232 Serial Communication

The P104-COM232-8 (PC/104-Plus) and 104I-COM232-8 (PCI-104) are PC/104-based eight channel RS-232 communication peripherals. Based on the XR17D158, the boards have eight enhanced 16550 UARTs, each with a set of modem signals (CTS, RTS, RI, DTR, DSR, CD). A 460Kb/s rate is guaranteed for all channels with up to 3K Ohm 1000pF loads. All interrupts may be monitored at a 32-bit status register. Each UART has both a 64 byte transmit and a 64 byte receive FIFO.The typical quiescent current draw from the user’s 5V supply is less than 60mA (with P1 and P2 disconnected). If every transmitter line is loaded with 3K Ohm, current draw should still be less than 150mA.

Linux drivers and sample programs are supplied with the card.


The provided Windows drivers are 100% compatible with the normal Microsoft-provided Serial Application Programming Interface. This means every program you’ve ever used with a standard serial port in Windows will also work with these ports, no problem. In addition, we provide several utility and sample programs to help you write your own code, if you’re not using something off-the-shelf.




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.


  • PCI Bus: Rev. 2.3
  • PC/104 Bus: Feedthrough only, no connection to the P104-COM232-8
  • I/O Space: Requires 4k

16550 Compatible

  • Data Size: 5, 6, 7 or 8 bits
  • Stop bit length: 1, 1.5 or 2 bits
  • Parity: Odd, even, none, forced to 1, or forced to 0
  • Break condition: On or off
  • Maximum Baud Rate: 460.8Kb/s (transceiver limit with full load)
  • Full Duplex Operation
  • Eight 64 Byte Transmit FIFO, 64 Byte Receive FIFO (16C550 FIFO = 16 Bytes)
  • S/W programmable FIFO trigger levels (16C550 trigger levels are fixed)
  • 12 standard registers for UART monitoring and control plus special registers
  • Loop-back mode
  • Scratch pad register

Transceiver I/O Characteristics

  • Receiver Input Resistance: 3K to 7K ohm
  • Receiver Input Sensitivity: ±3V
  • Receiver Input Voltage Range: ±15V
  • Driver Slew Rate: 30V/µS
  • Driver Load Impedance: 3K to 7K ohm
  • Driver Output Signal Level
    • Loaded ±5V
    • Unloaded ±15V
  • Transceiver ESD Characteristics
    • ±15KV Human Body Model
    • ±15KV Air Discharge
    • ±8KV Contact Discharge
  • Communications Interface: Eight channels split between two 40 pin male headers
  • Meets or exceeds the IEEE RS-232 standard


  • Operating Temperature Range:
    • Commercial: 0° to 70°C
    • Industrial: -40°C to +85°C
  • Humidity: 5% to 95%, non-condensing
  • Storage Temperature Range: -65°C to +125°C
  • Power Required: 50mA quiescent, 150mA maximum
  • Size: PC/104-Plus format, 3.5″ x 3.75″

CE testing & approval must be done at the system level, in the designed enclosure, and is not done on individual boards.

ModelDescriptionPrice (USD)

PC/104-Plus 8-Port RS-232 Serial Card


PCI-104 8-Port RS-232 Serial Card

Direct Connect
UTBK-40R 49 Screw terminal board, direct connect, removable, 40-pin
Cable Connect
C104-40F-D9M $25 Cable, Ribbon, 40-pin, Header F to 4 DB9M’s, 12″
C104-40F/D37F $19 Cable, Ribbon, 40-pin, Header F to DB37F
C104-DB37M/D9M $31 Cable, Round, DB37M to 4 DB9M, 3′
STB-40 $44 Screw terminal board, header connector, 40 pin
ADAP9 $19 Screw terminal board, DB9F to 9 terminals, single
ADAP9-2 $10 Screw terminal board, DB9F to 9 terminals, dual
PCI-P104-ADAP $129 PCI to PC/104-Plus adapter card.
Permits a PC/104-Plus board to be installed in a PCI slot
104-BP2 $99 Backplane with two side-by-side 16-bit PC/104 connectors
104-HDW-KIT(X) $10 Hardware kit for stacking boards:  Includes 4 screws, nuts and standoffs.
Specify Metric (M) or Standard (S).
MP104-DIN $19 DIN-rail mounting adapter
Model Options:
-T Extended operating temperature (-40°C to +85°C)