Reliable Real-time Systems Research Articles

Exception handling in RT-CDL

RT-CDL, a real-time design language, has been proposed for the design of reliable reactive systems. In this paper, we discuss the interesting features of RT-CDL from the point of view of real-time exceptions. We show how exceptions can be detected the handled in RT-CDL. Through illustrative examples, we are able to show how to (a) achieve various termination levels and propagate exceptions, (b) introduce intermediate checkpoints in a natural way, and (c) handle exceptions in a coordinated fashion, without introducing any extra language mechanisms. The language is amenable for compositional reasoning and can be used for the specification and handling of various real-time exceptions—thus, leading to the design of reliable real-time systems.

Real-Time Euclid: A language for reliable real-time systems

Real-Time Euclid, a language designed specifically to address reliability and guaranteed schedulability issues in real-time systems, is introduced. Real-Time Euclid uses exception handlers and import/export lists to provide comprehensive error detection, isolation, and recovery. The philosophy of the language is that every exception detectable by the hardware or the software must have an exception-handler clause associated with it. Moreover, the language definition forces every construct in the language to be time- and space-bounded. Consequently, Real-Time Euclid programs can always be analyzed for guaranteed schedulability of their processes. Thus, it is felt that Real-Time Euclid is well-suited for writing reliable real-time software.

The Control System for the Dedicated Synchrotron Radiation Storage Ring Bessy

BESSY is a 800 MeV electron-storage ring dedicated to research with synchrotron radiation in the VUV and soft X-ray region. The storage ring is fed by a 800 MeV separated function synchrotron with a clasical 20 MeV microtron as preinjector. The machines are remotely controlled by four minicomputers which are linked by a local network. The computers are connected to a commercially available electronic interface system. The general philosophy for the system design was determined by boundary conditions such as reliable processor hardware, reliable and powerful multi-user multi-programming real-time operating systems, well developed software tools, a ready-to-use distributed network with high throughput, compatibility of the electronic interface system, locally available service shops, and, if possible, the avoidance of assembly coding. This paper describes in detail the system which ultimately met these criteria and was subsequently implemented at BESSY.

Maintenance of reliable real time systems: Hardware versus software tradeoffs

The maintenance features in a high reliability real time control system form an important component in the total system. It is essential that software and hardware maintenance features function in an effective manner to ensure a high level of reliability in real time systems. Hardware maintenance features include redundant processors, self-checking circuits, diagnostic microcode etc., while software maintenance features include fault recovery programmes, audits, diagnostics etc. In this paper, we examine briefly the relationship of maintenance software to hardware in current high reliability real time systems, and how this relationship is likely to change in the future. Discussion in the paper centres around issues such as: factors that contribute to effective maintenance design; hardware characteristics that affect software; partitioning of maintenance functions between software, firmware and hardware; and current trends in maintenance of real time systems.

Program Fall Back Method in Real Time Systems

This paper presents a program fall-back method for improving reliability of real time systems. It presents a software structuring scheme for fall-back strategy and fall-back mechanisms which detecJt program errors, determine erroneous data, terminate the current task execution, restore erroneous data to nominal values, and continue task executions. The mechanisms are very simple, easy to implement and effective. This facility was applied to the test phase of a train traffic control system.

Program fall-back method in real time systems

This paper presents a program fall-back method for improving reliability of real time systems. It presents a software structuring scheme for fall-back strategy and fall-back mechanisms which detect program errors, determine erroneous data, terminate the current task execution, restore erroneous data to nominal values, and continue task executions. The mechanisms are very simple, easy to implement and effective. This facility was applied to the test phase of a train traffic control system.

Boiling-sodium tests with the BOR-60 reactor

These first experiments on the BOR-60 reactor have shown that in principle it is possible to detect the boiling of sodium from the acoustic and neutron fluctuations; useful information has been obtained on the character of the signals and the scope for using various processing methods. However, further measurements and calculations are needed before we can design a reliable real-time system for monitoring for sodium boiling in the core of a fast reactor.