GENERATION OF VECTOR PATTTERNS THROUGH RESEEDING OF MUETIPLE-POLYNOMIAL LINEAR FEEDBACK SHIFT REGIST

Abstract
In this paper we perform a comparative anal- ysis of the encoding efficiency of BIST schemes based on reseeding of single polynomial LFSR's as well as LFSR's with fully programmable polynomials. Full programma- bility gives much better encoding efficiency. For a test- cube with s carebits we need only s+4 bits in contrast to s+19 bits for reseeding of single polynomials, but since it involves solving systems of nonlinear equations it is not applicable to realistic cases. We propose a new BIST scheme where the generator can operate according to a number of primitive polynomials. The testcubes are en- coded as the polynomial identifier and a seed. We present models of the encoding efficiency of this scheme and de- monstrate, both theoretically and through extensive simu- lations, that such a scheme with 16 polynomials ap- proaches the efficiency of the scheme based on full poly- nomial programmability, essentially preserving the com- putational simplicity of single reseeding.

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