Embedded PCs for the industrial marketplace-an analysis of the STD bus

The enormous popularity of the IBM PC and its derivatives has created a large hardware and software base and significantly impacted the industrial controls marketplace. The original PC hardware has significant shortcomings for the industrial marketplace, however. PCs just aren't designed for high shock, vibration, and extreme temperature environments. The cards are long and not well retained. Fans and filters are usually required for cooling, and filters become clogged in dusty and dirty environments. Frequently, the important circuitry is located on a large "motherboard" that is poorly cooled and difficult to replace in the event of a failure. Packaging cannot meet even the simplest of NEMA standards and screw terminal I/O is almost nonexistent. The need for computer systems that retain PC compatibility but work reliably in extremes of temperature, shock, vibration, and electrical noise has resulted in many alternate bus structures and form factors being used. These include VME, STD, PC-104, "industrialized" PCs, and proprietary designs.