PC/104 48-ch. DIO with 3 Counters/Timers

  • Description
  • Specifications
  • Ordering Guide

Extensive software control of features is the highlight of this digital I/O module featuring 48 digital I/O lines, 3 16-bit counter/timers, and 3 independent PC bus interrupt inputs.

The 48 digital I/O lines on OMM are based on 2 82C55 ICs. They can be programmed for input or output in groups of 8 lines. Direct as well as strobed (latched) I/O modes are supported, and all I/O lines are connected to 10K Ohm pull-up resistors.

The 3 16-bit counter/timers are based on an 82C54 IC. They are controlled through a configuration register on OMM (in addition to the standard 82C54 configuration register). The counter inputs can be switched between external signals, the on-board 4MHz clock oscillator, or counter outputs, all under software control. By using one counter’s output as another counter’s input, you can cascade counters in software to create a 32-bit or 48-bit counter.

OMM also features programmable interrupt operations. A second software-controlled register on board configures up to 3 interrupt lines on the PC bus. Interrupts can be generated by the counter/timer outputs, digital I/O lines, or an external input line. This allows you to use a counter to generate bus interrupts at a programmed periodic rate, generate hardware interrupts under software control, or generate interrupts in response to an external event.

Chip 82C54-2
Counter/Timers 3, 16 bits wide
Maximum Input frequency. 10MHz
On-board Osc. 4MHz ±.01%
Signal Type TTL
Input Voltage Low: -0.5V min, 0.8V max
High: 2.0V min, 5.5V max
Input Current -200µA max (low), 2µA max (high)
Output Voltage Low: 0.0V min, 0.4V max
3.0V min, Vcc -0.4V max
Output Current ±2.5mA max, each line
Pullup Resistors 10KO all input lines
Digital I/O 2x 82C55A
Number of I/O Lines 48, TTL/CMOS Compatible
Direction All lines programmable for input in groups of 4 and 8
Output Current ±2.5mA max, each line
Pullup Resistors 10Kohms all input lines
Number of Interrupts 3
Pull-down Resistor 1KOhms resistor selectable via jumper on each interrupt
Interrupt Level 2-7
Interrupt Sources Counter/timer outputs, Interrupt input, or DIO lines CO (programmable)
Power Supply +5V ±5% @ 120mA typical all outputs open
Operating Temperature -40 to +85°C
Model Description
OMM-XT PC/104 48-ch. DIO with 3 Counters/Timers