With our CYDO 48H high-current digital output-only boards you can economically control 48 digital I/O lines from a single slot in your PC. This high-current board uses discrete logic in place of the Intel® 8255 chip to porvide a glitch-free high current sink (64mA). It is ideal for applications such as switching solid-state relays, lighting LEDs, and numerous other higher-current tasks which are beyond the capabilities of simple circuits such as the 8255. (8255 chips can source or sink 2.5mA per I/O line--1 TTL load; plenty of power for activating other chips, but not enough for LEDs or relays).
Dedicated control applications are better served by the CYDO 48H. I/O boards with 8255s on them must be set up in software, and they always initialize in input (high-impedance) mode. Also, 8255-based boards are subject to being reset by transient voltages on the output lines, such as when controlling an electromechanical relay switching an inductive load. Because the CYDO 48H board is fixed in an output state at all times, no programming is required to initialize the output registers. The output registers hold the state of the 8 bits most recently written to that port. The board maintains compatibility with the 8255 in software.