Enhanced Broadside Testing for Improved Transition Fault Coverage

The use of multiple scan chains was shown to improve the coverage of transition faults achieved by skewed-load tests. For broadside tests, the number of scan chains does not affect the transition fault coverage. We describe an enhanced broadside configuration under which increasing the number of scan chains helps increase the fault coverage. In the enhanced configuration, the first flip-flop of a scan chain operates in skewed-load mode while the other flip-flops operate in broadside mode. This provides flexibility in determining the value of the first flip-flop of every scan chain under the second pattern of a broadside test, thus increasing the transition fault coverage. We also describe a procedure that makes small modifications to a given scan chain configuration in order to improve the transition fault coverage.