Nonlinear compression block codes: Exact and random search strategy

The nonlinear block codes have significantly better testing abilities than the linear ones used in Built-In Self Test Equipment or test pattern decompressors. Unfortunately, no sufficiently effective deterministic code creation strategy has been discovered till now. This paper deals with a deterministic nonlinear code search strategy and a strategy based on extending linear compression codes by nonlinear check bits that improve the usability of decompressed patterns for testing circuits with more inputs. The earlier works used a purely or partially random search of the nonlinear check-bits truth tables to construct the first nonlinear structures. Here, we derive deterministic rules that can be used for the iterative process of code generation with no necessity of any random search for codes with the number of specified bits equal to three. We compare the code parameters of codes based on linear code extension, direct deterministic code search methods, and previously published results. The most extensive codes still need to be constructed with a partial random search strategy, but keeping the restrictions introduced in the paper causes the search to be substantially more efficient.