PCI-DIO-24D/H PCI 24-Bit Digital I/O Cards

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  • Universal PCI, PCI-X, 3.3V and 5V compatible
  • PCI Express versions available:
  • 24 bits of digital I/O
  • Four and eight bit ports independently selectable for I/O
  • All 24 I/O lines buffered by transceivers on the card
  • I/O buffers can be enabled/disabled under program control
  • Pull-ups on I/O lines
  • Resettable fused +5 VDC output available
  • PCI-DIO-24H compatible with industry standard I/O racks like Grayhill, Opto 22, Western Reserve Controls, Potter and Brumfield, etc.
  • Optional 10 MHz counters
  • Automatically detected under Windows
  • No base address or IRQ switches to set

Factory Options

  • RoHS compliant version
  • Support for Wind River VxWorks (call for ordering information)
Last updated on May 28, 2024, 5:03 pm


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These cards are 24-bit parallel, digital input/output cards designed for use in PCI-Bus computers. The difference between the models is that I/O connections to PCI-DIO24D are via a standard 37-pin D-sub connector while I/O connections to PCI-DIO24H are via a 50-pin connector. The cards are 4.80 inches long (122 mm) and may be installed in any 5V PCI-bus slot in IBM and compatible personal computers.

These cards contain a type 8255-5 Programmable Peripheral Interface (PPI) chip. They can be programmed to accept inputs or to provide outputs on three 8-bit ports: designated Ports A, B, and C. Port C can be further divided into two 4-bit nibbles.

Each I/O line is buffered by a type 74ABT245B tristate buffer transceiver capable of sourcing 32 mA or sinking 64mA. The buffers are configured under program control for input or output use according to direction control signals from the control register inside the PPI. Pull-ups (to +5 VDC) on the card assure that there are no erroneous outputs at power-up until the card is initialized by system software. Further, jumpers on the card provide a choice to either permanently enable the buffers or to tri-state them under program control.

Input/Output wiring connections for the PCI-DIO24D are via a 37-pin D-sub connector on the card mounting bracket. Either a 37-pin D-sub solder cup mating connector or an insulation-displacement ribbon cable can be used for I/O connections. Fused +5 VDC power is available at the I/O connector. A resettable on-board fuse is rated at 0.5A and can be reset by cycling computer power.

Input/Output wiring connections for PCI-DIO24H are via a 50-pin connector on the card mounting bracket. Insulation displacement ribbon cables can be used for I/O connections to termination panels such as ACCES’ model STA-50 Screw Terminal card. The pin connections are also compatible with ACCES A24A , Grayhill, OPTO22, Western Reserve Controls, Potter& Brumfield, etc opto-isolated module mounting racks. If needed for external circuits, fused +5VDC power is available at the I/O connector. The resettable 0.5A fuse can be reset by cycling computer power.


Optionally you can have one, two, or three 48-bit down counters configured as Event Counters (see the Block Diagram which shows one 48-bit counter) and can also be used as a Frequency source. To designate that you wish these counters, add -S01, -S02, and -S03 respectively to the model number. For example, a 24-bit digital input/output card with a 50-pin connector and one 48-bit counter is model PCI-DIO24H-S01.

The fused +5V output is available on all versions of the PCI-DIO-24D and H with the exception of the PCI-DIO-24D-S03. The -S03 on this card does not have +5V on the connector due to the limited number of pins on the DB37.




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 DAQ cards to VxWorks 7!

VxWorks 7 VxBus Gen 2 drivers, with easy-to-use API-libraries, are available for this product, including full source and sample code.

Designed to be compatible with our AIOWDM.dll Windows driver & API, this kernel module adds zero% CPU-cycle overhead to your VxWorks runtimes while allowing the lowest-latency hardware register access possible.

You can find more information about our VxWorks libraries and services on our Wind River Silver Partner page.

Digital Inputs (TTL Compatible)

  • Logic High: 2.0 to 5.0 VDC.
  • Logic Low: -0.5 to +0.8 VDC.
  • Input Load (Hi): 20 uA.
  • Input Load (Lo): -200 uA.

Digital Outputs

  • Logic High: 2.0 VDC min., source 32 mA.
  • Logic Low: 0.55 VDC max., sink 64 mA

Counter/Timers (Optional)

  • Type: 82C54 programmable interval counters (up to three)
  • Output Drive: Source 2.6 mA, Sink 24 mA
  • Input Gate: TTL/CMOS compatible
  • Clock: On-board, 1 MHz crystal-controlled oscillator
  • Active Count Edge: Negative edge (falling edge)
  • Minimum Clock Pulse Width: 30 nS high, 50 nS low
  • Timer Range: 48 bits
  • Power Output: Resettable 0.5A fused +5 VDC from computer bus


  • Operating Temperature Range: 0° to 50° C.
  • Storage Temperature Range: -40° to +65.6° C.
  • Humidity: Maximum 90% RH, without condensation.

Auxiliary Power Output

  • +5 VDC from the computer bus. Resettable fuse at 0.5A.

Power Required

  • Basic Unit: +5 VDC at 170 ma., if no current is drawn from the auxiliary fused +5 VDC output.
  • With One Counter: +5 VDC at 190 ma.
  • With Two Counters: +5 VDC at 210 ma.
  • With Three Counters: +5 VDC at 230 ma.

Regulatory Compliance

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

PCI, 24 Digitial I/O, DB37 Male


PCI, 24 Digitial I/O, DB37 Male, 1 counter


PCI, 24 Digitial I/O, DB37 Male, 2 counters


PCI, 24 Digitial I/O, DB37 Male, 3 counters


PCI, 24 Digitial I/O, 50-pin IDC Header, 1 counter


PCI, 24 Digitial I/O, 50-pin IDC Header, 1 counter


PCI, 24 Digitial I/O, 50-pin IDC Header, 2 counters


PCI, 24 Digitial I/O, 50-pin IDC Header, 3 counters

PCI-DIO-24H Accessories
Direct Connect Terminal Solution
UTBK-50 Direct connect 50-pin removable screw terminal board $49
Cable Connect Solutions
CAB50F-6 50 pin ribbon cable with female header connectors, 6 feet long $30
STB-50 DIN-rail mountable screw terminal board for 50-pin connector $39
STA-50 Configurable screw terminal board for 50-pin connector $79
Isolated and Relay Solutions
IIB-24 24 channel optical isolation board for each 50 pin header $149
ROB-24 24 channel electromechanical relay card for each 50 pin header
ROB-8A 8 channel electromechanical relay card for each 50 pin header
Accessory enclosure
T-BOX Steel enclosure with powder coated finish, use to mount STB-50 to panel $45


PCI-DIO-24D Accessories
Direct Connect Terminal Solution
ADAP37F-MINI Direct connect 37-pin removable screw terminal board
Cable Connect Solutions
CAB37-18 37-pin ribbon cable with female DB-37 connectors,  18″ long, other lengths available.
STB-37 DIN-rail mountable screw terminal board for 37-pin connector
STA-37 Configurable screw terminal board for 50-pin connector $79
Accessory enclosure
T-BOX Steel enclosure with powder coated finish, use to mount STB-50 to panel $45