A method of LFSR seed generation for hierarchical BIST

Abstract

In built-in self-test (BIST), pseudo-random patterns generated by a linear feedback shift register (LFSR) are applied to a circuit under test as test patterns. Since random pattern resistant faults (RPRFs) exist, reseeding is used to detect them. In general, seeds that when expanded by the LFSR will produce test patterns for detecting RPRFs are used for reseeding. So far, we have proposed a one-pass seed generation method for generating such seeds for scan-based BIST. In this paper, we introduce the concept of the one-pass method into seed generation for hierarchical BIST utilizing register-transfer level (RTL) information. The proposed method can identify untestable faults under the BIST environment and guarantees to generate seeds for detectable faults. In our experiments for several RTL benchmark circuits, we show that seeds generated by the proposed method can reduce test application time for RPRFs of the circuits.