In this paper we propose a novel method to reduce power consumption during scan testing caused by test responses at scan-out operation for logic BIST. The proposed method overwrites some flip-flops (FFs) values before starting scan-shift so as to reduce the switching activity at scan-out operation. In order to relax the fault coverage loss caused by filling new FF values before observing the capture values at the FFs, the method employs multi-cycle scan test with partial observation. For deriving larger scan-out power reduction with less fault coverage loss and preventing hardware overhead increase, the FFs to be filled are selected in a predetermined ratio. For overwriting values, we prepare three value filling methods so as to achieve larger scan-out power reduction. Experiment for ITC99 benchmark circuits shows the effectiveness of the methods. Nearly 51% reduction of scan-out power and 57% reduction of peak scan-out power are achieved with little fault coverage loss for 20% FFs selection, while hardware overhead is little that only 0.05%.

In this paper, we propose a method to diagnose a bridging fault between a clock line and a gate signal line. Assuming that scan based flush tests are applied, we perform fault simulation to deduce candidate faults. By analyzing fault behavior, it is revealed that faulty clock waveforms depend on the timing of the signal transition on a gate signal line which is bridged. In the fault simulation, a backward sensitized path tracing approach is introduced to calculate the timing of signal transitions. Experimental results show that the proposed method deduces candidate faults more accurately than our previous method.

Memory-based Programmable Logic Device (MPLD) is a new type of reconfigurable device constructed using a general SRAM array in a unique interconnect configuration. This research aims to propose approaches to guarantee the long-term reliability of MPLDs, including a test method to identify interconnect defects in the SRAM array during the production phase and a delay monitoring technique to detect aging-caused failures. The proposed test method configures pre-generated test configuration data into SRAMs to create fault propagation paths, applies an external walking-zero/one vector to excite faults, and identifies faults at the external output ports. The proposed delay monitoring method configures a novel ring oscillator logic design into MPLD to measure delay variations when the device is in practical use. The logic simulation results with fault injection confirm the effectiveness of the proposed methods.

Multi-cycle Test looks promising a way to reduce the test application time of POST (Power-on Self-Test) for achieving a targeted high fault coverage specified by ISO26262 for testing automotive devices. In this paper, we first analyze the mechanism of Stuck-at Fault Detection Degradation problem in multi-cycle test. Based on the result of our analysis we propose a novel solution named FF-Control Point Insertion technique (FF-CPI) to achieve the reduction of scan-in patterns by multi-cycle test. The FF-CPI technique modifies the captured values of scan Flip-Flops (FFs) during capture operation by directly reversing the value of partial FFs or loading random vectors. The FF-CPI technique enhances the number of detectable stuck-at faults under the capture patterns. The experimental results of ISCAS89 and ITC99 benchmarks validated the effectiveness of FF-CPI technique in scan-in pattern reduction for POST.