Measurement Computing's CIO-DIO48H provides 48 lines of digital I/O. The I/O is organized into two 24-line groups based on an 82C55 mode 0 emulation. Each 24-line group is divided into three eight-line ports labeled An, Bn and Cn, where n is either "1" for FIRSTPORT or "2" for SECONDPORT. Port C can be split into two four-bit nibbles Ñ Port C-HI and Port C-LO. Each of these ports may be individually programmed as input or output.
All digital inputs are LSTTL. The output signals are buffered high output drive TTL. The digital output drivers are 74S244 chips that can sink 64 mA and source 15 mA. The input buffers are 74LS373 chips and have standard high input impedance of the 74LS series devices.
On power up and reset, all I/O bits are set to input mode. 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.
All signals pass through a 50-pin connector.
