Mitigating Observability Loss of Toggle-Based X-Masking via Scan Chain Partitioning

Sae Eun Kim, Jaeyong Chung, Joon Sung Yang

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


The Toggle-based X-masking method requires a single toggle at a given cycle, there is a chance that non-X values are also masked. Hence, the non-X value over-masking problem may cause a fault coverage degradation. In this paper, a scan chain partitioning scheme is described to alleviate non-X bit over-masking problem arising from Toggle-based X-Masking method. The scan chain partitioning method finds a scan chain combination that gives the least toggling conflicts. The experimental results show that the amount of over-masked bits is significantly reduced, and it is further reduced when the proposed method is incorporated with X-canceling method. However, as the number of scan chain partitions increases, the control data for decoder increases. To reduce a control data overhead, this paper exploits a Huffman coding based data compression. Assuming two partitions, the size of control bits is even smaller than the conventional X-toggling method that uses only one decoder. In addition, selection rules of X-bits delivered to X-Canceling MISR are also proposed. With the selection rules, a significant test time increase can be prevented.

Original languageEnglish
Pages (from-to)1184-1192
Number of pages9
JournalIEEE Transactions on Computers
Issue number8
Publication statusPublished - 2018 Aug 1

Bibliographical note

Funding Information:
This work was supported in part by the Basic Science Research Program through the National Research Foundation of Korea by the Ministry of Education under Grant NRF-2015R1D1A1A01058856, in part by the Korea Institute for Advancement of Technology (KIAT) by the Korean Government (Motie:Ministry of Trade, Industry Energy, HRD Program for Software-SoC Convergence) under Grant N0001883, in part by the MOTIE (Ministry of Trade, Industry Energy (10080594) and KSRC(Korea Semiconductor Research Consortium) support program for the development of the future semiconductor device.

Publisher Copyright:
© 1968-2012 IEEE.

All Science Journal Classification (ASJC) codes

  • Software
  • Theoretical Computer Science
  • Hardware and Architecture
  • Computational Theory and Mathematics


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