Test Sequences with Reduced and Increased Switching Activity

Abstract

A functional test sequence for a synchronous sequential circuit is applied to the circuit in its functional mode of operation, and the switching activity during the application of the sequence is guaranteed not to exceed that possible during functional operation. It is thus possible to explore functional test sequences with increased switching activity as a way to enhance defect detection. Functional test sequences with decreased switching activity are also important for applications where power dissipation during test application must be limited. We describe a procedure that uses subsequences of a given test sequence to produce two test sequences, one with decreased and one with increased switching activity compared to the given test sequence. Both test sequences achieve the same fault coverage as the given test sequence. We also discuss a static test compaction process based on switching activity that preserves the switching activity of a test sequence.