A mixed mode BIST scheme based on reseeding of folding counters

In this paper a new scheme for deterministic and mixed mode scan-based BIST is presented. It relies on a new type of test pattern generator which rese mbles a programmable Johnson counter and is called folding counter. Both th e theoretical background and practical algorithms are presented to characte rize a set of deterministic test cubes by a reasonably small number of seed s for a folding counter. Combined with classical approaches for test width compression and with pseudo-random pattern generation these new techniques provide an efficient and flexible solution for scan-based BIST. Experimenta l results show that the proposed scheme outperforms previously published ap proaches based on the reseeding of LFSRs or Johnson counters.