Log In

Celebrating 45 Years

Follow us on Facebook for all the latest news, updates and promotions


Credit Cards Accepted


Aurora Probability in Northern Canada

Auroral forecast from AuroraWatch.ca


North America Aurora Map from
NOAA Space Weather Prediction Center

Aurora Map - NOAA




104-DIO-48S and 104-DIO-24S

acces i/o logo 
  US Pricelist
CND Pricelist
Privacy and Security Policy 

Change-Of-State Detecting Digital I/O Cards


  • 48 or 24 parallel lines of 82C55 digital I/O with tristate buffers prevent unintended control of external equipment
  • IRQ on input change of state (COS) eliminates the need for constant polling
  • High sink/source current 64mA/32mA
  • I/O pulled up to 5V for contact monitoring
  • Compatible with Opto-22 and other industry standard I/O racks
  • Factory Options: (call for pricing and availability)
    • 82C54 with three 16-bit counter/timers for event counting, frequency output, pulse width and frequency measurement
    • 0 to 70°C and -40 to 85°C versions available
    • Economy version without COS feature
    • Pull-down resistors on I/O lines

Digital I/O

The circuits use an 82C55A PPI with mode 0 supported. Ports A, B, C High, and C Low are buffered with 74ABT245 transceivers and pulled up to 5V.

COS Detection

Change of State Detection allows the card to generate an interrupt, port by port. Either direction will set the change of state interrupt. Your application can run much smoother by using this feature as processor overhead is greatly reduced, polling is not required.


The optional 82C54 has three-sixteen bit counters within one chip. These counters are useful for making frequency outputs, measuring frequency of square waves, pulse width outputs, pulse width measurements etc.


The 104-DIO-48S is supported in most operating systems and include a free DOS, Linux and Windows 95/98/Me/NT/2000/XP/2003 compatible software package. This includes sample programs and source code in "C" and Pascal for DOS, and Visual Basic, Delphi, C Builder, and Visual C for Windows. Also included is a graphical setup program in Windows.


Digital I/O

  • Programmable Peripheral Int.: 82C55A
  • Channels: 24 or 48, pulled up to 5V via 10K
  • Buffered Channels: 24 or 48 bits (ports A, B, C-High and C-Low)
  • Sink & Source Current: 64mA & 32mA
  • Modes supported: Mode 0
  • Change of State Detection: 48 Inputs (both 8255 groups, all 8 ports)
  • Throughput: Up to 1 MByte/sec
  • Power Output: Resettable fused 5V @ 500mA per 50 pin connector


  • Peripheral Interface Timer: Type 82C54
  • Counters: 3 x 16-Bit down counters
  • Clock Frequency: 1 MHz Time Base, available to the user
  • Software Support: Event Counter, Frequency Output, Frequency and Pulse Measurement
  • Max Input Frequency: 10MHz
  • Signal Type: TTL


  • Power Required: 5V @50mA Typical
  • Operating temperature: 0°C to 70°C, optionally -40°C to 85°C available
  • Storage temperature: -50° to 120°C
  • Interrupt Requests: Eleven channels, IRQ 3-7, 9-12, 14, 15
  • Interrupt Status Registers: Two; One 8bit for COS, One single bit for C/T

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

Acquisition Control Communications Engineering / Systems
USA Office

Address: 1480 Gulf Road, Suite 837,
PO Box 1364
Point Roberts, WA 98281

Western Canada - Vancouver BC

Tel:1.800.663.6001 or 1.604.925.6150
Address: 2454 Haywood Ave
West Vancouver, BC V7V 1Y1

Eastern Canada - Markham, Ontario

Tel:1.800.465.0164 or 1.905.513.7027