Column parity and row selection (CPRS): a BIST diagnosis technique for multiple errors in multiple scan chains

A BIST diagnosis technique is presented to diagnose multiple errors in multiple scan chains. An LFSR randomly selects outputs of multiple scan chains every scan cycle. The column parity and row parity of the selected scan outputs are observed every scan cycle and every scan unload, respectively. Compared with other techniques, which diagnose no more than 15% errors, CPRS correctly diagnoses all errors in the presence of 1% unknowns. The cost of this technique is area overhead and one additional output observed every scan cycle.