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Digital Input/Output Card


  • 64 channels of digital I/O
  • Eight 8-bit ports of directly addressable bi-directional I/O
  • Bit-by-bit programmable for input or output
  • I/O buffers can be enabled/disabled under program control
  • Compatible with industry standard I/O racks from Opto-22, Western Reserve Controls, DuTec, Gordos, Potter & Brumfield, etc
  • User selectable to occupy any eight consecutive I/O addresses.
  • Control and I/O ports separately addressable to allow I/O ports for multiple cards to occupy consecutive addresses
  • Four inputs may be directed to hardware interrupts

Model IOD-64 accepts up to 64 bits of Digital I/O and the card is organized into eight 8-bit ports. Input voltages can range up to 30 VDC. This card is particularly useful for interface between an ISA-Bus computer and industry-standard, optically-isolated, solid-state I/O module mounting racks. Up to four 16-position I/O racks can be controlled and each point is directly addressable by the host computer.

Variable I/O-mapped addressing allows you to select eight consecutive addresses plus a separate control port from any I/O addresses between 200 hex and 3FF hex. In addition, you can drive four of the host's interrupts from inputs applied to IOD-64. Read/Write Select Logic manages all data transmission between the computer and the I/O ports. There are five inputs to the select logic:

  • Reset: When this line goes high, either on power-up or during a low-line voltage loss, it clears the Output Control Latch disabling all output ports. This assures that there will be no spurious outputs.
  • Address Enable (AEN): When this line is driven low, it enables the PC I/O channel. The Read/Write Select Logic then checks the value on the address bus by comparing that address to the I/O Port and Control Addresses.
  • I/O Write Command (IOW): When this line is low and the address comparison is true, the IOD-64 card reads data from the data bus.
  • I/O Read Command (IOR): When this line is low and the address comparison is true, the IOD-64 card writes data to the data bus.
  • Address (ADDR): These ten lines are used to address the Control Port and I/O Ports.

When the Data Bus Buffer is enabled by the Read/Write Select Logic, it permits data transfer between the host computer and the IOD-64. The Output Control Latch disables any or all of the eight 8-bit I/O ports. Inputs to the Output Control Latch are:

  • Data from the host computer data bus.
  • When the PC-Reset line is high, it automatically clears the Output Control Latch which, in turn, disables all outputs as previously described.
  • When the Output Control Latch is enabled by the Read/Write Select Logic, it will disable individual ports as required by programming.

The IRQ Control, when enabled by the Read/Write Select Logic, routes external inputs received from any or all of the last four inputs of PORT 7 to IRQ4 through IRQ7 of the host computer.


Four 50-pin headers are provided; one for each group of 16 bits. Sixteen bi-directional data lines are alternated with 16 ground lines on each connector. Also, 5 VDC power is available and digital ground.


Digital Inputs

  • Logic High: 2.0 to 30 VDC
  • Logic Low: -0.5 to 0.8 VDC
  • Input Load (Hi): 20 uA
  • Input Load (Lo): -200 uA

Digital Outputs

  • Logic High: 2.5 VDC min. to 30.0 VDC (w/ external pull-ups), source 15 mA
  • Logic Low: 0.5 VDC max., sink up to 40 mA

Power Output

  • 5 VDC from computer bus (external 1A fast-blow fuse recommended)


  • Power Required: 5 VDC at 450 mA typical
  • Size: 13.1 inches long
  • Operating Temperature Range: 0o to 60 oC
  • Storage Temperature Range: -50o to 120 oC
  • Humidity: 0 to 90% RH, non-condensing

Regulatory Compliance

  • This product is in full compliance with CE requirements.

Part NumberPrice(USD)
View / Download Manual (in .pdf format)
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