Integration and Performance Issues

Putting mutually a real-time system represents the system engineer with hard software and hardware decisions. The allocation issues related with hardware for real-time systems are behind the scope of this book for additional information. Once the software parts have been allocated, detailed software requirements are established and a fundamental software design must be developed. Between many real-time design concerns are coordination among the real-time tasks, processing of system interrupts. Input or Output handling to ensure in which no data are lost, specifying the system’s external and internal timing constraints and ensuring the accuracy of its database.

Each and every real-time design concern for software must be applied in the circumstance of system performance. In several cases, the performance of a real-time system is measured as one or more time associated characteristics but other measures like as fault-tolerance may also be used.

Any real-time systems are designed for applications in that only the response time or the data transfer rate is critical. The Other real-time applications need optimization of both parameters under peak loading conditions. What is more real-time systems must handle their peak loads through performing a number of concurrent tasks.

Still the performance of a real-time system is determined above all through its data transfer rate and system response time, it is important to understand these 2 parameters. System response time is the time within that a system must detect an external or internal event and respond with an action. By Often event response and detection generation are easy. It is the processing of the information about the event to decide the appropriate response which may involve time-consuming, complex algorithms.

Between the key parameters which affect the response time are circumstance interrupt and switching latency. Circumstance switching involves and time overhead to switch between tasks and interrupt latency is the time lag before the switch is really possible. Other parameter which affects response time is the speed of computation and the speed of access to mass storage.

The data transfer rate indicates how quick parallel or serial data as well as digital or analog data must be moved into or out of the system. Hardware vendors often quote capacity and timing values for performance characteristics. Moreover hardware specifications for performance are commonly measured in isolation and are often of little value in determining overall real-time system performance. Thus Input or Output device performance and a host of other factors while important are only part of the story of real-time system design.

The Real-time systems are frequently needed to procedure a continuous stream of incoming data. The Design must ensure which data are not missed. Additionally a real time system must respond to events which are asynchronous. Thus, the arrival sequence and data volume cannot be simply predicated in advance.

The requirement for reliability moreover has spurred an ongoing debate about whether on-line systems like as automatic bank tellers and airline reservation systems also qualify as real-time. On one hand like on-line systems must respond to external interrupts within prescribed response times on the other of 1 second. On the other hand nothing catastrophic occurs if an on-line system fails to meet response necessities instead only system degradation results.