Test Time Minimization in Reconfigurable Scan Networks

Modern devices often include several embedded instruments, such as BISTs, sensors, and other analog components. New standards, such as IEEE Std. 1687, provide vehicles to access these instruments. In approaches based on reconfigurable scan networks, instruments are coupled with scan registers, connected into chains and interleaved with reconfigurable multiplexers, permitting a selective access to different parts of the chain. A similar scenario is also supported by IEEE Std. 1149.1-2013, where a test data register can be constructed as a chain of multiple segments, some of which can be excluded or mutually selected. The test of permanent faults affecting a reconfigurable scan network requires to shift test patterns throughout a certain number of network configurations. This paper presents a method to select the list of configurations needed to apply the complete test set in the minimum amount of clock cycles. The method is based on a graph representation of the problem. Experimental results on some benchmark networks are provided, together with a comparison with other approaches based on heuristics. The provided results can be effectively used to evaluate the test time of sub-optimal approaches