Covering undetected transition fault sites with optimistic unspecified transition faults under multicycle tests

Abstract

Transition faults require scan tests with two functional clock cycles between a scan-in and a scan-out operation to activate the faults and propagate their effects to observable outputs. Multicycle tests, with two or more functional clock cycles between scan operations, provide the following advantages. (1) They potentially increase the defect coverage by exercising the circuit at-speed for several functional clock cycles. (2) They allow test compaction to be achieved. (3) Multicycle tests can address features such as multiple clock domains and partial scan. (4) They create closer-to-functional operation conditions that are important for avoiding overtesting of delay faults.