A unified approach to the decomposition and re-decomposition of sequential machines

Abstract

A unified framework and associated algorithms are presented. This framework allows for a uniform treatment of arbitrary decomposition topologies operating at the state transition graph (STG) level, while targeting a cost function that is close to the eventual logic implementation. Previous work has targeted specific decomposition topologies via the formulation of decomposition as implicant covering with associated constraints. It is shown that this formulation can be used to target arbitrary desired topologies merely by customizing the constraints during implicant covering. It is also shown how this work relates to preserved partitions and covers traditionally used in parallel and cascade decompositions, and how this formulation establishes the relationship between state assignment and a finite state machine decomposition. Memory and CPU-time-efficient re-decomposition algorithms that operate on distributed-style specifications and which are more global than those presented in the past have been developed. These algorithms are implemented in the sequential logic synthesis system, FLAMES, that is being developed at UCB/MIT.<>