Built-in sequential fault self-testing of array multipliers

Microprocessor datapath architectures operate on signed numbers usually represented in two´s-complement or sign-magnitude formats. The multiplication operation is performed by optimized array multipliers of various architectures which are often produced by automatic module generators. Array multipliers have either a standard, nonrecoded signed (or unsigned) architecture or a recoded (modified Booth´s algorithm) architecture. High-quality testing of array multipliers based on a comprehensive sequential fault model and not affecting their well-optimized structure has not been proposed in the past. In this paper, we present a built-in self-testing (BIST) architecture for signed and unsigned array multipliers with respect to a comprehensive sequential fault model. The BIST architecture does not alter the well-optimized multiplier structure. The proposed test sets can be applied externally but their regular nature makes them very suitable for embedded, self-test application by simple specialized hardware which imposes small overheads. Two different implementations of the BIST architecture are proposed. The first implementation focuses on the test invalidation problem and targets robust sequential fault testing, while the second one focuses on test cost reduction (test time and hardware overhead).