Structure-Based Methods for Selecting Fault-Detection-Strengthened FF under Multi-cycle Test with Sequential Observation

FF-Control Point Insertion (FF-CPI) to Overcome the Degradation of Fault Detection under Multi-Cycle Test for POST

“…Finally, we show the experimental results on benchmark circuits to validate that the proposed methods can further reduce the number of scan-in patterns for achieving 90% stuck-at fault coverage compared to the SEQ-OB method presented in our previous paper [14], [15]. As a result, the proposed method is helpful to further shorten the TAT of POST.…”

“…However, observing all FFs will cause too large hardware overhead to practical use. In this paper, we conduct the partial observation technique presented in our previous papers [14]- [16] that only 20% of FFs of each circuit are selected for SEQ-OB to reduce the hardware overhead. The FFs used for SEQ-OB are selected by the FF selection algorithm presented in [14].…”

“…In [14], we have proposed a method for selecting the FFs for SEQ OB which can assist the fault coverage improvement by analyzing the circuit-structure w/o using simulation. In [15] and [16] we have proposed a DFT technique named Fault-Detection-Strengthened (FDS) method for strengthening the fault detection capability of multicycle test to enhance the effect of SEQ-OB technique.…”

“…In [15] and [16] we have proposed a DFT technique named Fault-Detection-Strengthened (FDS) method for strengthening the fault detection capability of multicycle test to enhance the effect of SEQ-OB technique. Also, we have developed the underlying technologies including the FDS flip-flop (FF) design and an original in-house tool named FVP-TPI (Fault-effects-Vanishing Point-TPI) to compute the most effective insertion point of FDS FFs for SEQ OB based on the FF selection algorithm proposed in [14].…”

“…Fault effects vanishing problem denotes that the fault effects excited at an intermediate capture cycle might disappear before it is propagated to the last capture cycle due to the expanded long propagation path under time-frame expansion combinational circuit. To address the fault effects vanishing problem, in [14]- [16], we have proposed the DFT techniques refers to SEQ-OB with FDS-FF design to directly observe and keep the faulty values propagated to FFs at multiple capture clocks so as to gather the faulty values before vanishing. Figure 2 shows the DFT for SEQ-OB and the design of FDS FF.…”