LFSR-Reseeding Scheme Achieving Low-Power Dissipation During Test

This paper presents a new low-power test-data-compression scheme based on linear feedback shift register (LFSR) reseeding. A drawback of compression schemes based on LFSR reseeding is that the unspecified bits are filled with random values, which results in a large number of transitions during scan-in, thereby causing high-power dissipation. A new encoding scheme that can be used in conjunction with any LFSR-reseeding scheme to significantly reduce test power and even further reduce test storage is presented. The proposed encoding scheme acts as the second stage of compression after LFSR reseeding. It accomplishes two goals. First, it reduces the number of transitions in the scan chains (by filling the unspecified bits in a different manner). Second, it reduces the number of specified bits that need to be generated via LFSR reseeding. Experimental results indicate that the proposed method significantly reduces test power and in most cases provides greater test-data compression than LFSR reseeding alone