Maintaining proximity to functional operation conditions under enhanced-scan tests based on functional broadside tests

In a circuit with enhanced-scan, any two-pattern test can be applied to detect delay faults. However, the tests may deviate substantially from functional operation conditions, and result in overtesting. Functional broadside tests create functional operation conditions during their functional clock cycles by using reachable states as scan-in states. To maintain a proximity to functional operation conditions under enhanced-scan, the procedure described in this paper generates enhanced-scan tests that differ from functional broadside tests only in small numbers of values. Experimental results show that it is possible to achieve high transition fault coverage under this constraint.