Real-time systems

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Integrated Real-time Systems

Integrated Real-time Systems

Abstract Integrated Real-time Systems are systems in which applications with different levels of criticality, co- exist. These systems must support strong partitioning concept, temporal and spatial both, at its core design. Scheduling applications in such systems requires two level hierarchical scheduling to satisfy tem- poral constraints and a secure memory management technique to satisfy spatial constraints. Two such systems, Open System Architecture and Strongly Partitioned Integrated Real-time Systems, are dis- cussed. Algorithms to schedule soft aperiodic tasks without affecting scheduling of hard real-time tasks are overviewed. A minimal second generation kernel is required on top of which, different operating systems can run efficiently for different applications. Microkernels which have spatial partitioning and protected communication mechanism, such as SPIRIT microkernel, L4 and fiasco are described in detail.
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Real Time Systems pdf

Real Time Systems pdf

limitations of different techniques. There are a number of small examples in the text to illustrate the theory and each chapter ends with a set of exercises. The idea for the book came originally from material used for the M.Sc. module on real-time systems at the University of Warwick. This module has now been taught by several of the authors over the last three years and has been attended by both students and visiting participants. However, it was planned that the book would contain a more comprehensive treatment of the material than might be used in a single course. This al- lows teachers to draw selectively on the material, leaving some parts out and others as further reading for students. Some possible course selections are outlined in Chapter 1 but many more are possible and the choice will be governed by the nature of the course and the interests and preparation of the students. Part of the material has been taught by the authors in advanced undergraduate courses in computer science, computer engineer- ing and related disciplines; selections have also been used in several different postgrad- uate courses and in short courses for industrial groups. So the material has been used successfully for many different audiences.
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A framework for scheduling real-time systems

A framework for scheduling real-time systems

VII. C ONCLUSION In this paper, based on satisfiability modulo theories (SMT), we provide a framework to design scheduling for real- time systems. In the framework, the problem of scheduling is treated as a satisfiability problem. After using first-order language to formalize the satisfiability problem, a SMT solver is employed to solver such a problem. An optimal schedule can be generated based on a solution model returned by the SMT solver. To demonstrate the practicality of the framework, we give design guidelines for real-time systems with multi- processor. Through the demonstration, the framework is found flexible and sufficiently general to apply to different kinds of real-time systems. By giving the practical design guidelines, we believe that our framework can benefit system designers to efficiently design scheduling.
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Scheduling for Embedded Real-Time Systems

Scheduling for Embedded Real-Time Systems

which time is almost irrelevant. “Real time” is slightly more specific than “reactive” because it generally identifies a sys- tem composed of several distinct, often cooperating, tasks. In addition, real-time systems are usually assumed to be nonterminating; the duration for which they operate is usu- ally long enough that it is effectively infinite. Scheduling in this domain consists of finding an execution order for a set of mutually exclusive, sometimes suspendable tasks. These tasks are characterized by various parameters such as ex- pected activation times (maybe periodic, maybe not), max- imum required execution times, and deadlines by which they must be completed after activation. Since the programs are nonterminating, issues such as memory usage and dead- lock avoidance also become very important. For example, a task might produce data at a faster rate than it is consumed, or circular dependencies might arise in which each task is waiting for another to finish, resulting in early program ter- mination—an error in most cases.
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Software engineering for real-time systems

Software engineering for real-time systems

SOFTWARE ENGINEERING for REAL-TIME SYSTEMS (© J.E.Cooling 2003) Introduction to real-time systems - slide 29 LED driver DAC (2) Stepper motor control I 2 C serial interface Sound genera[r]

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Designing Fluctronic Real-Time Systems

Designing Fluctronic Real-Time Systems

8. Conclusions In summary, this paper presents a feedback control real-time scheduling (FCS) framework for adaptive real-time systems. An advantage of the FCS framework is its use of feedback control theory (rather than ad hoc solutions) as a scientific underpinning. We apply a control theory based design methodology to systematically design FCS algorithms to satisfy desired transient and steady state performance specifications of real-time systems. In particular, we establish an analytical model and analyses of FCS algorithms, which are major challenges and key steps for the design of adaptive real-time systems. Based on our model, we identify different types of real-time applications where each FCS algorithm can be applied. Performance evaluation results demonstrate that our analytically tuned FCS algorithms provide robust steady and transient state performance guarantees for periodic and aperiodic tasks even when the task execution time varied by as much as 100% from the estimation.
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Adaptive multiprocessor real-time systems

Adaptive multiprocessor real-time systems

CHAPTER 1 INTRODUCTION The goal of this dissertation is to extend research on multiprocessor real-time systems in order to enable such systems to adapt tasks’ processor shares—a process called reweighting —in re- sponse to both external and internal stimuli. The particular focus of this work is on adaptive systems that are deployed in environments in which tasks may frequently require significant share changes. Such environments are commonplace in computationally-intensive multimedia applications. Prior to the research in this dissertation, no multiprocessor reweighting algo- rithms had been proposed that could change task shares with bounded overhead. In this dissertation, we extend prior work on uniprocessor and multiprocessor systems to construct reweighting algorithms with minimal overhead for several different types of multiprocessor systems. Furthermore, we examine how feedback and optimization techniques can be use to determine, at run time, which reweighting events are needed. Finally, we evaluate the pro- posed adaptive scheduling algorithms by using two multimedia applications developed at The University of North Carolina at Chapel Hill: the Whisper human tracking system (Vallidis, 2002) and the Virtual Exposure Camera (VEC) night vision system (Bennett and McMillan, 2005).
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Optimal composition of real-time systems

Optimal composition of real-time systems

Abstract Real-time systems are designed for environments in which the utility of actions is strongly time-dependent. Recent work by Dean, Horvitz and others has shown that anytime algorithms are a useful tool for real-time system design, since they allow com- putation time to be traded for decision quality. In order to construct complex systems, however, we need to be able to compose larger systems from smaller, reusable anytime modules. This paper addresses two basic problems associated with composition: how to ensure the interruptibility of the composed system; and how to allocate computation time optimally among the components. The first problem is solved by a simple and general construction that incurs only a small, constant penalty. The second is solved by an off-line compilation process. We show that the general compilation problem is NP-complete. However, efficient local compilation techniques, working on a single program structure at a time, yield globally optimal allocations for a large class of programs. We illustrate these results with two simple applications.
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Model Checking Real-Time Systems

Model Checking Real-Time Systems

regions together, which is often relevant in practical situations. We explain in Sect. 7 how properties of timed automata can be verified in practice. Finally, we conclude this chapter with two powerful extensions of timed automata: first, weighted timed automata allow for modeling quantitative constraints beyond time; since resource (e.g., energy) consumption is usually tightly bound to time elapsing, timed automata provide a convenient frame- work for modeling such quantitative aspects of systems. Unlike hybrid systems (see Chap. 28hybrid), weighted timed automata still enjoy some nice decidabil- ity properties (in restricted settings though), as we explain in Sect. 8. Then in Sect. 9 we present timed games, which are very powerful and convenient for dealing with the controller synthesis problem (see Chap. 25gamesynth) in a timed framework. Timed games also provide an interesting way of model- ing uncertainty in real-time systems, assuming worst-case resolution of the uncertainty while still trying to benefit from non-worst-case situations.
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Real Time Systems - 7th Sem - ECE - VTU - Unit 1 - Introduction to Real Time Systems - ramisuniverse

Real Time Systems - 7th Sem - ECE - VTU - Unit 1 - Introduction to Real Time Systems - ramisuniverse

RTS definition (Cooling – 1991): Real-time systems are those which must produce correct responses within a Real-time systems are those which must produce correct responses within a definite time limit. Should computer responses exceed these time bounds then definite time limit. Should computer responses exceed these time bounds then performance degradation and/or malfunction results

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A Review of Priority Assignment in Real-Time Systems

A Review of Priority Assignment in Real-Time Systems

3 University of Modena, Italy. rob.davis@york.ac.uk, liliana.cucu@inria.fr, marko.bertogna@unimore.it, alan.burns@york.ac.uk Abstract - It is over 40 years since the first seminal work on priority assignment for real-time systems using fixed priority scheduling. Since then, huge progress has been made in the field of real-time scheduling with more complex models and schedulability analysis techniques developed to better represent and analyse real systems. This tutorial style review provides an in-depth assessment of priority assignment techniques for hard real-time systems scheduled using fixed priorities. It examines the role and importance of priority in fixed priority scheduling in all of its guises, including: pre- emptive and non-pre-emptive scheduling; covering single- and multi-processor systems, and networks. A categorisation of optimal priority assignment techniques is given, along with the conditions on their applicability. We examine the extension of these techniques via sensitivity analysis to form robust priority assignment policies that can be used even when there is only partial information available about the system. The review covers priority assignment in a wide variety of settings including: mixed-criticality systems, systems with deferred pre-emption, and probabilistic real-time systems with worst- case execution times described by random variables. It concludes with a discussion of open problems in the area of priority assignment.
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Chapter 19: Real-Time Systems. Overview of Real-Time Systems. Objectives. System Characteristics. Features of Real-Time Systems

Chapter 19: Real-Time Systems. Overview of Real-Time Systems. Objectives. System Characteristics. Features of Real-Time Systems

19.13 Silberschatz, Galvin and Gagne ©2005 Operating System Concepts – 7 th Edition, Jan 1, 2005. Interrupt Latency[r]

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Probabilistic Real-Time Systems

Probabilistic Real-Time Systems

Ø   Identify the existing probabilistic techniques for multi-core. Ø   Ensure the requirements of the PROARTIS single-core[r]

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DISTRIBUTED REAL-TIME SYSTEMS

DISTRIBUTED REAL-TIME SYSTEMS

If two or more devices try to send at the same time, a collision occurs and the frames are discarded. Each device then waits a random amount of time and retries until successful in getting its transmission sent. Ethernet is inherently stochastic. It cannot provide a known upper bound on transmission time.

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Real Time Systems Exam

Real Time Systems Exam

Part 3 – Design Questions We are planning to design a new light-voice controlling system. The voices will basically coordinate the crossing of a road by blind people. Suppose the crossing will be operated by two coordinated systems: a light system and a voice system. The light controlling system is an ordinary set of traffic lights intended for vehicles, but with the amber light flashing before the lights change over to green. These lights operate in cycles and display the colors in the order:

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Failures In Real Time Systems

Failures In Real Time Systems

This paper is going to focus on a few significant major failures in applied real time operating systems both old and new. To start with let us take a look at how the software in the Mars Pathfinder failed in its objective, and then look at how the Boeing 737MAX failed and then a transition to how these issues were solved or could have been prevented.

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Real-Time Systems / Real-Time Operating Systems EE445M/EE380L.12, Spring 2018

Real-Time Systems / Real-Time Operating Systems EE445M/EE380L.12, Spring 2018

as shown below. Sketch (only) the modifications/extensions of basic OS routines as needed. c) Assuming your priority-scheduled system is running a sporadic/aperiodic foreground task T i with execution time E i at each priority level 0 ≤ i < N, what is the maximum jitter experienced by a periodic foreground task T m at priority m? Assume that there are no background threads.

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REAL TIME SYSTEMS. Piotr MALECKI

REAL TIME SYSTEMS. Piotr MALECKI

When using msync, one should use pages within the same address and length as specified in the call to the mmap function to ensure that the entire mapped region is synchronized. (Similar[r]

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OPC and Real-Time Systems in LabVIEW

OPC and Real-Time Systems in LabVIEW

Download your NI LabVIEW application onto the embedded real-time controller for stand-alone data logging, monitoring, and advanced control. Plus, connect to virtually any sensor type with the wide variety of I/O modules, such as thermocouples, resistance temperature detectors (RTDs), strain gages, 4-20 mA sensors, and a variety of digital signals from 5-30 VDC and 0-250 VAC. The Compact FieldPoint I/O modules filter, calibrate, and scale raw sensor signals to engineering units and perform self-diagnostics to look for problems, such as an open thermocouple.

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Linux for Embedded and Real-Time Systems

Linux for Embedded and Real-Time Systems

available to support the production of Linux software for embedded systems; they range from use-case tools like ArgoUml, Poseidon, etc; to debugging tools like gdb (with remote debugg[r]

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