A design for testability technique for test pattern generation with LFSRs

Test sets for built-in self-test (BIST) test pattern generation (TPG) are normally pseudorandom or truncated pseudoexhaustive. In this work, the authors propose a pseudorandom TPG scheme which is based on the idea of ordering appropriately the cells of a linear feedback shift register (LFSR) in order to control the percentage of linear dependencies in the generated patterns. The LFSR cell ordering is done prior to the circuit´s layout phase, in accordance with the design for testability principles. The proposed pseudorandom scheme compares favorably with the use of truncated pseudoexhaustive test sets with or without cell reordering