Diagnosing faulty functional units in processors by using automatically generated test sets

Microprocessor technology is increasingly used for many applications; the large market volumes call for cost containment in the production phase. Process yield for processor production is, however, far from ideal. To increase it fault diagnosis is an important means, since it can allow both process characterization and product repair by the usage of backup resources. This paper presents a novel methodology to discriminate faulty modules, rather than gates, in a microprocessor based on the automatic construction of diagnostic software-based test sets. The approach exploits a post-production test set, designed for software-based self-test, and an infrastructure IP to perform the diagnosis. An initial diagnostic test set is built, and then iteratively refined resorting to an evolutionary method. Experimental results are reported in the paper showing the feasibility and effectiveness of the approach for an Intel i8051 processor core.