Eugenio Villar

Systematic embedded software generation from SystemC

The embedded software design cost represents an important percentage of the embedded-system development costs [1]. This paper presents a method for systematic embedded software generation that reduces the software generation cost in a platform-based HW/SW codesign methodology for embedded systems based on SystemC. The goal is that the same SystemC code allows system-level specification and verification, and, after SW/HW partition, SW/HW co-simulation and embedded software generation. The C++ code for the SW partition (processes and process communication including HW/SW interfaces) is systematically generated including the user-selected embedded OS (e.g.: the eCos open source OS).

A framework for heterogeneous specification and design of electronic embedded systems in SystemC

This work proposes a methodology which enables heterogeneous specification of complex, electronic systems in SystemC supporting the integration of components under different models of computation (MoCs). This feature is necessary in order to deal with the growing complexity, concurrency, and heterogeneity of electronic embedded systems. The specification methodology is based on the SystemC standard language. Nevertheless, the use of SystemC for heterogeneous system specification is not straightforward. The first problem to be addressed is the efficient and predictable mapping of untimed events required by abstract MoCs over the discrete-event MoC on which the SystemC simulation kernel is based. This mapping is essential in order to understand the simulation results provided by the SystemC model of those MoCs. The specification methodology proposes the set of rules and guidelines required by each specific MoC. Moreover, the methodology supports a smooth integration of several MoCs in the same system specification. A set of facilities is provided covering the deficiencies of the language. These facilities constitute the methodology-specific library called HetSC. The methodology and associated library have been demonstrated to be useful for the specification of complex, heterogeneous embedded systems supporting essential design tasks such as performance analysis and SW generation.

RTOS modeling in SystemC for real-time embedded SW simulation: A POSIX model

SystemC is committed to support the requirements for an integrated, HW/SW co-design flow, thus allowing the development of complex, multiprocessing, Systems-on Chip (MpSoC). To make this possible, efficient modeling and simulation methodologies for Real-Time, Embedded (RT/E) SW in SystemC have to be developed, so that the designer can verify and refine the application SW together with the rest of the elements of the platform. Accurate modeling of the application SW requires an accurate model of the RTOS. Nevertheless, low-level, dynamic timing characteristics of the RTOS such as time-slicing, priority-based preemptive scheduling, interrupts and exceptions do not have a direct implementation in SystemC.In this paper, techniques are proposed to accurately model the detailed RTOS functionality on top of the SystemC execution kernel. The model allows timed-simulation and refinement of the RT/E SW code in SystemC. The simulation technology has been applied to the development of a high-level, POSIX simulation library in SystemC. The library allows the designer a fast, sufficiently accurate, timed simulation of the application SW running on top of POSIX. As most current RTOSs support this standard, the library is portable to different development frameworks. The library provides the required infrastructure for a complete, multiprocessing, HW/SW co-simulation environment at different abstraction levels using SystemC.

System-level performance analysis in SystemC

As both the ITRS and the Medea+ DA Roadmaps have highlighted, early performance estimation is an essential step in any SoC design methodology based on International Technology Roadmap for Semiconductors (2001) and The MEDEA+ Design Automation Roadmap (2002). This paper presents a C++ library for timing estimation at system level. The library is based on a general and systematic methodology that takes as input the original SystemC source code without any modification and provides the estimation parameters by simply including the library within a usual simulation. As a consequence, the same models of computation used during system design are preserved and all simulation conditions are maintained. The method exploits the advantages of dynamic analysis, that is, easy management of unpredictable data-dependent conditions and computational efficiency compared with other alternatives (ISS or RT simulation, without the need for SW generation and compilation and HW synthesis). Results obtained on several examples show the accuracy of the method. In addition to the fundamental parameters needed for system-level design exploration, the proposed methodology allows the designer to include capture points at any place in the code. The user can process the corresponding captured events for unrestricted timing constraint verification.

MULTICUBE: Multi-objective Design Space Exploration of Multi-core Architectures

Technology trends enable the integration of many processor cores in a System-on-Chip (SoC). In these complex architectures, several architectural parameters can be tuned to find the best trade-off in terms of multiple metrics such as energy and delay. The main goal of the MULTICUBE project consists of the definition of an automatic Design Space Exploration framework to support the design of next generation many-core architectures.

A framework for embedded system specification under different models of computation in SystemC

This paper presents a heterogeneous specification methodology built on top of the standard SystemC kernel. The methodology enables abstract specification supporting heterogeneity, which in this context entails the ability to describe and connect parts of the system specification under different models of computation (MoCs). A main and distinguishing contribution of the methodology is that the support is provided while maintaining the standard kernel of SystemC unchanged, by means of a set of specification rules and a heterogeneous support library built on top of the SystemC standard library. This is possible thanks to an abstraction technique that can integrate any new MoC that can be abstracted over the underlying discrete-event simulation kernel. Primitives, guidelines and rules of the specification methodology, including those related to heterogeneous support, and the basis of the abstraction technique are described. Experimental results demonstrate the benefits of the methodology

POSIX modeling in SystemC

Early estimation of the execution time of real-time embedded SW is an essential task in complex, HW/SW embedded system design. Application SW execution time estimation requires taking into account the impact of the underlying RTOS. As a consequence, RTOS modeling is becoming an active research area. SystemC provides a framework for multiprocessing, HW/SW co-simulation at several abstraction levels. In this paper, a SystemC library for POSIX modeling and simulation is presented. By using the library, the SystemC specification using POSIX functions is converted automatically into a timed simulation estimating the execution time of the application SW running on the POSIX platform. The library works directly on the source code. Therefore, it provides an early and fast estimation of the performance of the system as a consequence of the architectural mapping decisions. Although accuracy is lower than when using lower-level techniques, it supports high-level design-space exploration as simulation time is significantly less than RT (ISS) simulation.

The COMPLEX methodology for UML/MARTE Modeling and design space exploration of embedded systems

The design of embedded systems is being challenged by their growing complexity and tight performance requirements. This paper presents the COMPLEX UML/MARTE Design Space Exploration methodology, an approach based on a novel combination of Model Driven Engineering (MDE), Electronic System Level (ESL) and design exploration technologies. The proposed framework enables capturing the set of possible design solutions, that is, the design space, in an abstract, standard and graphical way by relying on UML and the standard MARTE profile. From that UML/MARTE based model, the automated generation framework proposed produces an executable, configurable and fast performance model which includes functional code of the application components. This generated model integrates an XML-based interface for communication with the tool which steers the exploration. This way, the DSE loop iterations are efficiently performed, without user intervention, avoiding slow manual editions, or regeneration of the performance model. The novel DSE suited modelling features of the methodology are shown in detail. The paper also presents the performance model generation framework, including the enhancements with regard the previous simulation and estimation technology, and the exploration technology. The paper uses an EFR vocoder system example for showing the methodology and for demonstrative results.

The COMPLEX reference framework for HW/SW co-design and power management supporting platform-based design-space exploration

The consideration of an embedded devices power consumption and its management is increasingly important nowadays. Currently, it is not easily possible to integrate power information already during the platform exploration phase. In this paper, we discuss the design challenges of todays heterogeneous HW/SW systems regarding power and complexity, both for platform vendors as well as system integrators. As a result, we propose a reference framework and design flow concept that combines system-level power optimization techniques with platform-based rapid prototyping. Virtual executable prototypes are generated from MARTE/UML and functional C/C++ descriptions, which then allows to study different platforms, mapping alternatives, and power management strategies. Our proposed flow combines system-level timing and power estimation techniques available in commercial tools with platform-based rapid prototyping. We propose an efficient code annotation technique for timing and power properties enabling fast host execution as well as adaptive collection of power traces. Combined with a flexible design-space exploration (DSE) approach our flow allows a trade-off analysis between different platforms, mapping alternatives, and optimization techniques, based on domain-specific workload scenarios. The proposed framework and design flow has been implemented in the COMPLEX FP7 European integrated project.

AADL Simulation and Performance Analysis in SystemC

Due to the increasing complexity of embedded systems, new design methodologies have to be adopted, since traditional techniques are no longer efficient. Model-based engineering enables the designer to confront these concerns using the architecture description of the system as the main axis during the design cycle. Defining the architecture of the system before its implementation enables the analysis of constraints imposed on the system from the beginning of the design cycle until the final implementation. AADL has been proposed for designing and analyzing SW and HW architectures for real-time mission-critical embedded systems. Although the Behavioral Annex improves its simulation semantics, AADL is a language for analyzing architectures and not for simulating them. In this paper, AADS, an AADL simulation tool is presented. AADS supports the performance analysis of the AADL specification throughout the refinement process from the initial system architecture until the complete, detailed application and execution platform are developed. In this way, AADS enables the verification of the initial timing constraints during the complete design process.