Fault Diagnosis for RAMs Using Walsh Spectrum

In this paper, we show a method to locate a single stuckat fault of a random access memory (RAM). From the fail-bitmaps of the RAM, we obtain their Walsh spectrum. For a single stuck-at fault, we show that the fault can be identified and located by using only the 0-th and 1-st coefficients of the spectrum. We also show a circuit to compute these coefficients. The computation time is O(2n), where n is the number of bits in the address of the RAM. The computation time is much shorter than one that uses a logic minimization method. key words: memory test, diagnosis, BIST, fail-bitmap, Walsh spectrum