Online BIST for Embedded Systems

0740-7475/98/$10.00 © 1998 IEEE 17 EMBEDDED SYSTEMS are computers incorporated in consumer products or other devices to perform application-specific functions. The product user is usually not even aware of the existence of these systems. From toys to medical devices, from ovens to automobiles, the range of products incorporating microprocessor-based, softwarecontrolled systems has expanded rapidly since the introduction of the microprocessor in 1971. The lure of embedded systems is clear: They promise previously impossible functions that enhance the performance of people or machines. As these systems gain sophistication, manufacturers are using them in increasingly critical applications— products that can result in injury, economic loss, or unacceptable inconvenience when they do not perform as required. Embedded systems can contain a variety of computing devices, such as microcontrollers, application-specific integrated circuits, and digital signal processors. A key requirement is that these computing devices continuously respond to external events in real time. Makers of embedded systems take many measures to ensure safety and reliability throughout the lifetime of products incorporating the systems. Here, we consider techniques for identifying faults during normal operation of the product—that is, online-testing techniques. We evaluate them on the basis of error coverage, error latency, space redundancy, and time redundancy.