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ISA Bus 8-Input A/D Converter and Counter/Timer Card


  • Eight A/D channels, 12-bit resolution
  • Programmable scan rate
  • Foreground/background operation
  • Seven bits digital I/O
  • Three 16-bit programmable counter/timers
  • Can assert interrupts
  • Event, period, pulse, and pulse-width counting
  • Designed, made, supported, and manufactured in the USA
AIO8 is an economical multifunction, moderate-speed, multiplexed analog-to-digital converter card with digital I/O and with counter/timers. It can be used with ISA-bus computers. The card is 7" long and requires one slot in the computer. All external connections are made through a standard 37-pin D-type connector at the rear of the computer. PC bus power (+5V, +12V, and -12V) is provided at the rear connector. This allows additional user-designed interfaces for input signal conditioning, expansion multiplexers, etc.


AIO8 accepts eight analog inputs. The full-scale input for all analog channels is ±5V (0.00244V resolution). Inputs are single-ended with a common ground and can withstand a continuous overload of ±30V and brief transients of several hundred volts. The A/D converter is a 12-bit successive-approximation type with sample and hold input. Conversion time is typically 25 microseconds (35 microseconds max.) and, depending on the software and the computer used, throughput rates up to 4,000 samples/second are attainable.


Seven bits of discrete digital I/O are provided; one 4-bit output port and one 3-bit input port. Each output can drive five standard TTL loads. The output port, if not used to select analog input expansion channels, may be used for general purpose applications.


The card supports up to eight AIM-16 or LVDT-8 analog input expansion cards (or mixtures). A 3-bit standard LSTTL logic output from AIO8 is used to select any one of the LVDT inputs at an LVDT-8 and a 4-bit LSTTL logic output from AIO8 is used to select one of 16 analog input channels at the AIM-16. The eight-input analog multiplexer on the AIO8 card is software addressable and an input expansion card can be connected to each input for a maximum of 128 analog data channels in the system. To accommodate more than 128 inputs, either a second AIO8 (and companion input expansion cards) can be used or you may wish to consider using the AD12-16.


A type 8254 counter/timer chip is included on the card. This chip contains three separate 16-bit down counters. One of the counters is connected to a submultiple of the system bus clock and all I/O functions of the other two counters are available to you at the I/O connector. The counters can be used to generate periodic interrupt requests, for event counting, pulse and waveform generation, frequency and period measurements, etc. Timed A/D conversions may be initiated by the counter/timer if a jumper is installed on the I/O connector. Also, software provided by ACCES includes means to use these counters to provide programmable gain commands to the instrumentation amplifier on board the AIM-16 expansion multiplexers.


Interrupts are supported from external inputs. Selection of input levels IRQ2 through IRQ7 is made by jumper on the card. Interrupts are software enabled and disabled. An interrupt request may be canceled by either:
    a) Computer reset signal, or
    b) Writing a command word to the card; i.e., by either updating the channel selection on the associated AIM-16 expansion card or on the AIO8 multiplexer.

Available Reference Manuals

Available Software Downloads

Drivers and Downloads

Full list of available Downloads: Software Packages, Drivers, Manuals, and other documents

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.


Analog Inputs

  • A/D Type: Successive approximation.
  • Resolution: 12-bit binary. Coding is offset binary.
  • Number of Channels: 8 single-ended inputs w/common ground.
  • Voltage Range: ±5 VDC.
  • Overvoltage Protection: ±30 VDC.
  • Input Impedance: 10 Megohm or 100 nA at 25°C.
  • Accuracy: 0.02% of reading ±1 LSB.
  • Linearity: ±1 LSB.
  • Temp. Coefficients: ±10 µV/°C zero stability. ±25 µV/°C gain stability.

Digital Inputs / Outputs

  • Logic Low: 0 to 0.4V at 8 mA sink.
  • Logic High: 2.4 to 5.0V at 0.4 mA source.
  • Logic Low: 0 to 0.4V at 8 mA sink.
  • Logic High: 2.4 to 5.0V at 0.4 mA source.


  • No. of Counters: Three 16-bit down counters. Clock input to one is ½ the PC system clock frequency; clock inputs to the others can come from external sources.
  • Input Voltage Levels:
    Low: 0 to 0.8V.
    High: 2.4 to 5.0V.
  • Output Voltage Levels:
    Low: 0 to 0.45V at up to 2.0 mA sink.
  • Clock Period: 125 nSec min.
  • Clock Rise and Fall Time: 25 nSec max.


  • Operating Temperature Range: 0° to 60°C.
  • Storage Temperature Range: -20° to +70°C.
  • Humidity: 0 to 90% RH, non-condensing.

Regulatory Compliance

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

Acquisition, Control, Communication: Engineering and Systems