On the feasibility of combining on-line-test and self repair for logic circuits

Integrated circuits and systems implemented by using nano-technologies show a combination of known and new faults effects, which affect their reliability and their operational life time, specifically in safety-critical applications. Transient fault effects such as single and multiple event upsets (SEUs and MEUs) require fast error detection and compensation. Permanent faults may occur due to early life time failures on one side and stress-induced rapid aging on the other hand. They need to be compensated by repair technologies, preferably using “fresh” resources for the replacement of faulty functional units. As self repair is typically not a fast process and requires extra time while the system is off-line, on-line fault compensation must also catch and handle permanent faults that occur during “hot” operation. If on-line-test and error compensation on one side and repair technologies on the other hand are implemented independently, the resulting overhead in redundant circuitry becomes prohibitively high. In the following paper we therefore introduce a new concept of logic design which can meet the essential demands at reasonable cost using a flexible allocation of redundancy.