Increasing fault coverage during functional test in the operational phase

A key issue in many safety-critical applications is the test of the ICs to be performed during the operational phase: regulations and standards often explicitly describe fault coverage figures to be achieved. Functional test (i.e., a test exploiting only functional inputs and outputs, without resorting to any Design for Testability) is often the only viable solution, unless a strict cooperation exists between the system company and the device provider. However, purely functional test often shows several limitations due to the limited accessibility that it can gain on some input/output signals. This paper proposes a hybrid approach, in which a suitable hardware module is added outside a microcontroller to increase its functional testability during the operational phase. Experimental results gathered on a couple of cases-of-study are reported, showing the feasibility of the method.