Luciano Lavagno

Scheduling for embedded real-time systems

The authors review several approaches to control-oriented and dataflow-oriented software scheduling to determine whether a given technique can satisfy deadlines, throughput, and other constraints for embedded real-time systems.

Algorithms for synthesis of hazard-free asynchronous circuits

A teclinique for the synthesis of asynchronous sequential circuits from a Signal Transition Graph (STG) specificatmion is described. We give algorithms for synthesis and hazard removal, able to produce hazard-free circuits with the bounded wire-delay model, requiring the STG to be live, safe and to have the unique state coding property. A proof tliat, contrary to previous beliefs, STG persistency is not necessary for hazard-free implementation is given.

Guidelines for a graduate curriculum on embedded software and systems

The design of embedded real-time systems requires skills from multiple specific disciplines, including, but not limited to, control, computer science, and electronics. This often involves experts from differing backgrounds, who do not recognize that they address similar, if not identical, issues from complementary angles. Design methodologies are lacking in rigor and discipline so that demonstrating correctness of an embedded design, if at all possible, is a very expensive proposition that may delay significantly the introduction of a critical product. While the economic importance of embedded systems is widely acknowledged, academia has not paid enough attention to the education of a community of high-quality embedded system designers, an obvious difficulty being the need of interdisciplinarity in a period where specialization has been the target of most education systems. This paper presents the reflections that took place in the European Network of Excellence Artist leading us to propose principles and structured contents for building curricula on embedded software and systems.

Solving the state assignment problem for signal transition graphs

The authors propose a novel framework to solve the state assignment problem arising from the signal transition graph (STG) representation of an asynchronous circuit. They first solve the STG state assignment problem by minimizing the number of states in the corresponding finite-state machine (FSM) and by using a critical race-free state assignment technique. State signal transitions may be added to the original STG. A lower bound on the number of signals necessary to implement the STG is given. The technique significantly increases the applicability of STGs for specifying asynchronous circuits.<<ETX>>

Modeling micro-controller peripherals for high-level co-simulation and synthesis

Mapping the behavior on an embedded system involves hardware-software partitioning and assignment of software and hardware tasks to different components. In particular, software tasks in embedded controllers are mostly assigned to a micro-controller. However, some micro-controller peripherals are implemented with partly programmable components that can be regarded as very simple co-processors with limited instruction sets and capabilities. Embedded system designers are used for mapping some simple software tasks onto these simple co-processors, obtaining overall performances that can be orders of magnitude superior to the ones obtained mapping all software tasks to the microcontroller itself. We propose a methodology to specify, simulate, and partition tasks that can be implemented on programmable micro-controller peripherals such as timing processing units (TPUs). Following our general philosophy, we let the designer propose a partition, and we provide an environment: to efficiently simulate and evaluate a particular implementation choice; and to automate downstream synthesis for software, hardware, as well as peripheral programming routines.

A unified signal transition graph model for asynchronous control circuit synthesis

Both low-level (analysis-oriented) and high-level (specification-oriented) models for asynchronous circuits and the environment where they operate, together with strong equivalence results between the properties at the low levels, are described. One interesting side result is the precise characterization of classical static and dynamic hazards in terms of the model. Consequently the designer can check the specification and directly decide if the behavior of any implementation will depend, e.g., on the delays of the signals described by such specification.<<ETX>>

Baseband analog front-end and digital back-end for reconfigurable multi-standard terminals

Multimedia applications are driving wireless network operators to add high-speed data services such as EDGE (E-GPRS), WCDMA (UMTS) and WLAN (IEEE 802.11a,b,g) to the existing network. This creates the need for multi-mode cellular handsets that support a wide range of communication standards, each with a different RF frequency, signal bandwidth, modulation scheme, etc. This in turn generates several design challenges for the analog and digital building blocks of the physical layer. In addition to the above mentioned protocols, mobile devices often include Bluetooth, GPS, FM-radio and TV services that can work concurrently with data and voice communication. Multi-mode, multi-band, and multi-standard mobile terminals must satisfy all these different requirements. Sharing and/or switching transceiver building blocks in these handsets is mandatory in order to extend battery life and/or to reduce cost. Only adaptive circuits that are able to reconfigure themselves within the handover time can meet the design requirements of a single receiver or transmitter covering all the different standards while ensuring seamless inter-operability. This paper presents analog and digital base-band circuits that are able to support GSM (with EDGE), WCDMA (UMTS), WLAN and Bluetooth using reconfigurable building blocks. The blocks can trade off power consumption for performance on the fly, depending on the standard to be supported and the required QoS (Quality of Service) level.

Constraints specification at higher levels of abstraction

We are proposing a formalism to express performance constraints at a high level of abstraction. The formalism allows specifying design performance constraints even before all low level details necessary to evaluate them are known. It is based on a solid mathematical foundation, to remove any ambiguity in its interpretation, and yet it allows quite simple and natural specification of many typical constraints. Once the design details are known, the satisfaction of constraints can be checked either by simulation, or by formal techniques like theorem proving, and, in some cases, by automatic model checking.

MIS-MV: optimization of multi-level logic with multiple-values inputs

Techniques are presented for the optimization of multi-level logic with multiple-valued input variables. The motivation for this is to tackle the input encoding problem in logic synthesis, where binary codes need to be found for the different values of a symbolic input variable. Multi-level multiple-valued optimization is used to generate constraints that are used to determine the codes. The state assignment problem in sequential logic synthesis can be approximated as an input encoding problem by ignoring the next state field, which is reasonable when the primary output logic, dominates the next state logic. A novel technique is presented for extracting common factors with multiple-valued variables, and it is shown how other multi-level optimization techniques are easily extended with multiple-valued variables. These ideas have been implemented as algorithms in the MIS-MV program. Practical issues are also presented regarding implementation. Experimental results are also given.<<ETX>>

Symbolic minimization of multilevel logic and the input encoding problem

Techniques for the optimization of multilevel logic with multiple-valued input variable is presented. The motivation for this is to tackle the input encoding problem in logic synthesis, where binary codes must be found for the different values that a symbolic input variable can take. It is shown how the other multilevel optimization techniques are easily extended with multiple-valued variables. These ideas have been implemented as algorithms in the program MIS-MV. The practical issues involved in the implementation of these ideas are discussed, and results of using MIS-MV for input encoding on benchmark examples presented. >