Measurement Computing's CIO-DIO24/CTR3 has 24 digital I/O lines, one 82C55 parallel-interface chip. A 82C54 counter chip provides three 16-bit down counters.
Each 82C55 chip controls 24 CMOS/TTL-compatible digital I/O pins. The 82C55 is configured as two 8-line ports and two 4-line ports. Each port is programmable for input or output.
All I/O bits are set to input mode (high impedance) on power up and reset. If you are using the board to control items that must be OFF on reset, install pull-down resistors. The board is equipped with open locations where you can install SIP resistor networks for either pull-up or pull-down.
You can configure the counter 0 input to be clocked from an internal 10 MS/s crystal oscillator or from an external clock source.
All signals pass through a 37-pin connector.
