Soonhoi Ha - Handbook of Hardware/Software Codesign

Springer Science+Business Media Dordrecht 2017

Soonhoi Ha 1

Abstract

Hardware/Software Codesign (HSCD) is an integral part of modern Electronic System Level (ESL) design flows. This chapter will review important aspects of hardware/software codesign flows, summarize the historical evolution of codesign techniques, and subsequently summarize each of its major branches of research and achievements that later will be presented in detail by different parts of this Handbook of Hardware/Software Codesign.

Acronyms

As the name implies, Hardware/Software Codesign (HSCD) denotes design methodologies for electronic systems that exploit the trade-offs and the synergy of Hardware (HW) and Software (SW). Typically, the application functionality is partitioned into software components that are running on the processor cores and hardware components that are used to accelerate some parts of the application or to provide interfaces to the environment. In the traditional design practice for such systems, software is usually designed after the hardware architecture is fixed as illustrated in Fig..

The design starts with a set of specifications and requirements on the functional and nonfunctional properties of the target system. The first step is to determine the appropriate algorithm to meet the functional specification if it is not given. Afterward, system architects typically determine a hardware architecture that would satisfy the functional requirements while optimizing the design objectives such as cost minimization and/or energy minimization. The decision is usually made based on the profiling information of the algorithms to be implemented and their computational complexity as well as resource requirements and constraints. It is typically influenced by past design experience of similar systems. How to partition the functionality into software and hardware components is also determined manually in this step.

After this HW/SW partitioning for the determined hardware architecture, two groups of engineers work independently to design and implement the hardware components and software components. The software group waits to finalize the design until a hardware prototype is made by the hardware group since the software usually contains hardware-dependent components. After the hardware prototype is built, the entire software that consists of the system software and the application software is ported. After porting is completed, the system undergoes testing and verification that checks whether the system satisfies the functional and nonfunctional requirements. It rarely happens that testing and verification succeeds at the first attempt. If a test fails, the causes of the failure need to be found, which is a difficult and tiresome task for all engineers involved in the design. If it turns out that the hardware architecture and HW/SW partitioning decisions need to be changed, it is required to go back to the starting point of the design loop to iterate the design process.

As the system complexity increases, the above traditional design flow faces several challenges. It is evident that the critical path in the design process becomes prohibitively long and costly in case multiple iterations of the sequential flow are performed from HW and SW development, software porting, and testing. And the design quality mostly depends on the expertise of the architect since the target architecture and HW/SW partitioning are decided manually.