Synthesis of Testable Finite State Machine Through Decomposition

This paper reports an efficient state encoding scheme for synthesis of large FSMs with enhanced BIST quality. A metric, referred to as degree-of-freedom (DOF) (Roy et al., 2002) in FSM states has been employed to quantify the BIST quality. Analysis of DOF enables efficient encoding of FSM states and gives solution to the problem of handling unreachable/hard-to-exit/hard-to-reach state codes of an FSM. The synthesis of a large FSM is realized through decomposition. DOF analysis for the individual component sub-FSM states is done to reduce the complexity of synthesis. A scheme is proposed for encoding the sub-FSM states that significantly improves testability of the synthesized resultant FSM, displaying the terminal behavior as the original FSM