Generation of Functional Broadside Tests for Transition Faults

摘要

Scan design allows a circuit to be tested using states that the circuit cannot enter during functional operation. It was observed that nonfunctional operation during testing may cause excessive currents that can cause a good chip to fail the test because of voltage droops caused by the excessive current demand. A good chip may also fail due to the propagation of signal transitions along nonfunctional long paths, especially during at-speed testing. This problem is studied in this paper in the context of tests for transition faults. A method for determining transition faults that are untestable under functional operation-conditions is described. Two procedures for generating transition-fault tests that use only functional operation conditions are also described. The first procedure accepts as input a broadside test set for transition faults. The second procedure accepts as input a test sequence for the nonscan circuit. Although such a test sequence is more complex to generate and simulate, it results in higher numbers of faults detected under functional operation conditions.