The real-time system is a software system the correct functioning of the system depends on the results produced by the system the time at which these results are produced. Many of the popular design "methodologies" were developed as design techniques for applications programs, operating systems, and related programs (compilers, editors, loaders, etc).
This method support constructs such as hierarchical decomposition, modularity, information hiding, and data abstraction. These design concepts are important for real-time and distributed systems but do not explicitly incorporate methods to deal with performance characteristics or problems of network configuration and Communication protocols. Problems encountered in designing real-time and distributed systems.
According to Franta, a distributed system consists of a collection of nearly autonomous processors but communicate to achieve a coherent computer system. Each processor possesses private memory, and processors communicate through an interconnection network. Major issues to be addressed in designing a distributed system includes specifying the technology of the communication network, establishing foods for accessing the shared communication channel, allocating application processing function to processing nodes the network and aestivation goals for crossing communication and synchronization.
The design of a distributed system is further complicated by the need to allocate network functionality between hardware and software components of the network. For example, trade-offs of costs and complexity between hardware and software components of network interconnection devices are not obvious. Traffic between nodes must be analyzed to establish the necessary communication rates.
Reliability issues such as coping with the loss of your communication link or Loss of a processing node must be considered. Mechanisms for message flow control, error control in response to file use of redundancy checks in arriving messages, systems status monetary, and network Diagnostic techniques must be considered. In particular, the mechanism for addressing processes in remote nodes, allocation of the communication network various nodes, messages parity errors checks, system status monitoring must all be specified.
By definition, Real-Time systems must provide specified amounts of computation within Fixed time intervals. Real-Time systems typically sense and control external devices, respond to external events, share processing time between multiple tasks. Processing demands are both cyclic and event-driven. Event-driven activities may occur in bursts, does acquiring a high ratio of peak to average processing.
Real-Time systems often form distributed networks, local processes may be associated with sensing devices and actuators. A real-time network for process control may consist of several minicomputers and microcomputers connected to one or more large processors. Each small processors may be connected to a cluster of real-time devices. In this manner, processing power can be placed at a natural site in the system, and data can be processed at the point of reception rather than at the Central node, thus reducing communication bandwidth needs.
Decomposition criteria for distributed real-time systems include the need to maintain process simplicity and to minimize inter-process communication bandwidths by communicating simple process messages rather than raw data.
Systems that monitor and control the environment.
Inevitably associated with hardware devices
Time is critical. Real-Time systems must respond within specified times.
Hard Real-Time systems may have to program in assembly language 2 to ensure that deadlines are met. Languages such as C allow efficient programs to be written but do not have a construct to support concurrency or shared Resource Management. Process control systems often utilize communication networks having fixed, static topology, and known capacity requirements. In contrast, more elaborate Real-Time systems provide dynamic configuration of the network topology and support and predictable load demands.
Many process control systems are designed with only two-level of abstraction, which Comprises basic system functions and application programs. It is not clear whether a two-level Hierarchy is the result of process control system characteristics are process control designer characteristics.
The SREM system discussed below was developed due to support analysis of real-time system requirements. Important features of SERM for specifying Real-Time systems include the f flow-oriented approach of stimulus-response and the ability to associate performance characteristics and validation conditions with particular points in the processing sequence.
Several notations have been developed to support the analysis and design of real-time and distributed systems. They include RSL, SDLP, NPN, communication ports, and denotation developed by Kramer and Cunningham. Most of these mutations are state warranted because a real-time system can be thought of as processing several processing States, with the transitions between States triggered by external stimuli.
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Real-time and distributed system design The real-time system is a software system the correct functioning of the system depends on the results produced by the system the time at which these results are produced ... Read More
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