Scan chain based at-speed diagnosis in the presence of scan output compaction schemes

The use of scan chains in diagnosis operations turns to be an important yield enhancement factor in nanotechnologies. However, scan chain output compaction schemes drastically reduce the ability to effectively diagnose (locate) faults in a defective circuit. In addition, scan chains are not friendly to at-speed diagnosis, where timing faults must be located. A new at-speed scan chain diagnosis technique is presented, which guarantees the maximum diagnostic resolution independently of the presence of any scan chain output compaction schemes.