On-the-Fly Reseeding: A New Reseeding Technique for Test-Per-Clock BIST

In this paper we present a new reseeding technique for test-per-clock test pattern generation suitable for at-speed testing of circuits with random-pattern resistant faults. Our technique eliminates the need of a ROM for storing the seeds since the reseeding is performed on-the-fly by inverting the logic value of some of the bits of the next state of the Test Pattern Generator (TPG). The proposed reseeding technique is generic and can be applied to TPGs based on both Linear Feedback Shift Registers (LFSRs) and accumulators. An efficient algorithm for selecting reseeding points is also presented, which targets complete fault coverage and allows to well exploiting the trade-off between hardware overhead and test length. Using experimental results we show that the proposed method compares favorably to the other already known techniques with respect to test length and the hardware implementation cost.