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18th International Conference on VLSI Design held jointly with 4th International Conference on Embedded Systems Design (VLSID'05)
Distance Restricted Scan Chain Reordering to Enhance Delay Fault Coverage
Kolkata, India
January 03-January 07
ISBN: 0-7695-2264-5
Wei Li, University of Iowa
Seongmoon Wang, NEC Research Labs
Srimat T. Chakradhar, NEC Research Labs
Sudhakar M. Reddy, University of Iowa
This paper presents a new technique to improve the delay fault coverage by re-ordering flip-flops in a scan chain. Unlike prior techniques where scan flip-flops can be reordered arbitrarily to form a new scan chain order, we restrict the distance by which a scan flip-flop can be moved to create the new scan chain order. The distance restriction makes it practical to make post-synthesis, local layout modifications to accommodate the new scan chain order. It also minimizes the routing overhead required for the new scan chain order. Given a post-synthesis scan chain order, we re-order flip-flops to minimize the number of undetectable faults due to test pattern dependency. Although the distance restriction limits the number of possible new scan chain orders, the fault coverage achieved by using our new local scan chain re-ordering method is comparable or even higher than prior methods. Moreover the scan order obtained with our method also improves the coverage of stuck-open faults. Experimental results show that the proposed method can improve delay fault coverage by up to 21.8% for ISCAS 89 circuits.
Citation:
Wei Li, Seongmoon Wang, Srimat T. Chakradhar, Sudhakar M. Reddy, "Distance Restricted Scan Chain Reordering to Enhance Delay Fault Coverage," vlsid, pp.471-478, 18th International Conference on VLSI Design held jointly with 4th International Conference on Embedded Systems Design (VLSID'05), 2005
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