IIRO-8, Eight Isolated Digital Input and Eight Relay Output ISA Card

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  • Eight optically isolated, non-polarized digital inputs
  • Eight electromechanical relay outputs
  • 60V isolation
  • Can detect input state change and assert interrupt
  • Designed, made, supported, and manufactured in the USA
Last updated on February 15, 2024, 2:09 pm


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IIRO-8 is a low-cost, half-size card that provides isolated input and output interface for PC/XT/AT and compatible computers. The card provides eight optically-isolated inputs for AC or DC control signals and eight electromechanical relay outputs. Inputs are optically isolated from each other and from the computer. They can be driven by either AC or DC signals and are not polarity sensitive. Thus inputs can be driven from standard 12/24 VAC control transformers as well as by DC voltages. Input voltage range is 5 to 24 Volts (rms). External resistors connected in series can be used to extend this input range.

Each input circuit contains a switchable slow/fast filter that has a 10 millisecond time constant. The filter must be selected for AC inputs but may be switched out in order to obtain faster response for DC inputs. The filter is also useful for slowly-changing noisy DC inputs. A DIP switch on the card permits filter selection on a channel-by-channel basis. Alternatively, you can globally switch all filters in or out under software control.

Another feature of this card is the ability to detect if a state change occurs at any one or more of the inputs and, in turn, assert an interrupt. This is very useful when monitoring for contact closures/openings because it is not necessary to continuously poll the inputs. When the IIRO-8 detects a state change, the resulting interrupt request can be used to initiate a poll of the inputs to determine which line(s) changed. After the interrupt has been serviced, the interrupt latch can be cleared by a software write.

The electromechanical relay outputs are comprised of five Form C SPDT outputs and three Form A SPST (normally open) type. On/Off status of the relays can be read back. All relays are de-energized at power turn-on. IIRO-8 occupies four consecutive addresses in I/O space. The base address can be selected anywhere within the address range 000-3FF (hex). Read and write operations are done on an 8-bit byte-oriented basis. All input/output connections are via a single 37-pin D connector at the rear of the card.




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.

Digital Inputs

  • Number of inputs: 8
  • Type: Non-polarized, optically isolated from each other and from the computer. (not TTL/CMOS compatible)
  • Voltage Range: 5 to 24V DC or AC (50 to 1000 Hz)
  • Isolation: 60V channel-to-ground or channel-to-channel
  • Input Resistance: 470 ohms in series with two diodes and an LED
  • Response Time: 20 mSec w/filter, 10 uSec w/o filter

Relay Outputs

  • Number of outputs: 8
  • Contact Rating: 2A carry current, bifurcated, gold clad, silver palladium
  • Contact Arrangement: Channels 0-4 are SPDT Form C and channels 5-7 are SPST Form A
  • Contact Rating: Initial 100 milliohms maximum
  • Contact Life: mech’l: 5 million operations minimum; elect’l: 500,000 operations minimum at full load
  • Operating Time: 2 milliseconds maximum
  • Release Time: 1 milliseconds maximum


  • When enabled by software and by installation of level-select jumpers, interrupts are generated when digital inputs change state.

Power Required

  • +5VDC @ 1 A (all relays ON)


  • Ambient Temperature: Operating: 0 to +50 C
  • Storage: -20 to +70 C
  • Humidity: 0 to 90 percent (non-condensing)
  • Weight: Approx. 8 oz.
  • MOQ’s may be required.
ModelDescriptionPrice (USD)

Eight Isolated Digital Input and Eight Relay Output ISA Card