A diagnostic test generation system

Abstract

A diagnostic automatic test pattern generation (DATPG) system is constructed by adding new algorithmic capabilities to conventional ATPG and fault simulation programs. The DATPG aim to generate tests to distinguish fault pairs, i.e., two faults must have different output responses. Given a fault pair, by modifying circuit netlist a new single fault is modeled. Then we use a conventional ATPG to target that fault. If a test is generated it distinguishes the given fault pair. A fast diagnostic fault simulation algorithm is implemented to find undistinguished fault pairs from a fault list for a given test vector set. We use a proposed diagnostic coverage (DC) metric, defined as the ratio of the number of fault groups to the number of total faults. The diagnostic ATPG system starts by first generating conventional fault coverage vectors. Those vectors are then simulated to determine the DC, followed by repeated applications of diagnostic test generation and simulation. We observe improved DC in all benchmark circuits.