An Efficient Design Methodology for Complex Sequential Asynchronous Digital Circuits

Abstract

Asynchronous digital logic as a design alternative offers a smaller circuit area and lower power consumption but suffers from increased complexity and difficulties related to logic hazards and elements synchronization. The presented work proposes a design methodology based on the speed-independent sequential logic theory, oriented toward asynchronous hardware implementation of complex multi-step algorithms. Targeting controller-centric devices that perform data-driven non-linear execution, the methodology offers a CSP language-based controller workflow description approach and the specification of a project implementation template supported by a two-stage design process. First, the CSP layer describes complex speed-independent controller behavior offering better scalability and maintainability than the STG model. Second, the component-oriented design template specifies functional elements\u27 structural organization and emphasizes the divide-and-conquer philosophy, streamlining large and complex devices\u27 design and maintenance. Finally, the implementation process is divided into two stages: a rapid development and functional verification stage and a synthesizable codebase stage. Additionally, a case study design of a split-transaction MESI cache coherency controller and its analysis are presented to validate the proposed methodology. The testing phase compares synthesized and routed gate-level asynchronous and synchronous implementations. For models synthesized to work with the same speed, the asynchronous circuit area is 20% smaller with lower power consumption at approximately 18% of the synchronous reference. The synchronous version synthesized for performance is 3.5 times faster, at the cost of a large increase in area and power usage. The results prove the methodology\u27s ability to deliver working complex asynchronous circuits competitive in the chip area and power characteristics

    Similar works