COHRA: hardware-software co-synthesis of hierarchical distributed embedded system architectures

Hardware-software co-synthesis of an embedded system architecture entails partitioning of its specification into hardware and software modules such that its real-time and other constraints are met. Embedded systems are generally specified in terms of a set of acyclic task graphs. For medium-to-large scale embedded systems, the task graphs are usually hierarchical in nature. The embedded system architecture, which is the output of the co-synthesis system, may itself be non-hierarchical or hierarchical. Traditional non-hierarchical architectures create communication and processing bottlenecks, and are impractical for large embedded systems. Such systems require a large number of processing elements and communication links connected in a hierarchical manner, thus forming a hierarchical distributed architecture, to meet performance and cost objectives. In this paper, we address the problem of hardware-software co-synthesis of hierarchical distributed embedded system architectures from hierarchical or non-hierarchical task graphs. We show how our co-synthesis algorithm can be easily extended to consider fault tolerance or low power objectives or both. Although hierarchical architectures have been proposed before, to the best of our knowledge, this is the first time the notion of hierarchical task graphs and hierarchical architectures has been supported in a co-synthesis algorithm