On output response compression in the presence of unknown output values
Irith Pomeranz, Sandip Kumar Kundu, Sudhakar M. Reddy · Proceedings - ACM IEEE Design Automation Conference · 2002
A circuit may produce unknown output values during simulation of an input sequence due to an unknown initial state or due to the existence of tri-state elements. For circuits tested using BIST, unknown output values make it impossible to determine a single unique signature for the fault free circuit. To accommodate unknown output values in a BIST scheme, we describe a procedure for synthesizing a minimal logic block that replaces unknown output values by a known constant. The proposed procedure ensures that the BIST scheme will be able to detect all the faults detectable by the input sequence applied to the circuit while allowing a single unique signature to be obtained.