Cyclic-CPRS : A Diagnosis Technique for BISTed Circuits for Nano-meter Technologies

A cyclic-CPRS (column parity row selection) technique is presented to diagnose built-in self tested (BISTed) circuits, even in the presence of many unknowns and transient errors. The novel cyclic scan chains retain the transient errors and unknowns in the CUT until they are fully diagnosed. Instead of masking the unknowns, Cyclic-CPRS directly diagnoses the unknowns as if they were errors. Direct diagnosis of unknowns not only eliminates the masking circuitry but also enhances the diagnosis resolution. Experimental results show that Cyclic-CPRS is very successful even in the presence of 10% errors and unknowns. The proposed technique is especially suitable for nanometer technologies, in which transient errors and systematic defects are becoming serious problems.