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Employing Two ‘Sandwich Delay’ Mechanisms to Enhance Predictability of Embedded Systems Which Use Time-Triggered Co-Operative Architectures

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DOI: 10.4236/jsea.2011.47048    2,822 Downloads   5,923 Views   Citations
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In many real-time resource-constrained embedded systems, highly-predictable system behavior is a key design requirement. The “time-triggered co-operative” (TTC) scheduling algorithm provides a good match for a wide range of low-cost embedded applications. As a consequence of the resource, timing, and power constraints, the implementation of such algorithm is often far from trivial. Thus, basic implementation of TTC algorithm can result in excessive levels of task jitter which may jeopardize the predictability of many time-critical applications using this algorithm. This paper discusses the main sources of jitter in earlier TTC implementations and develops two alternative implementations – based on the employment of “sandwich delay” (SD) mechanisms – to reduce task jitter in TTC system significantly. In addition to jitter levels at task release times, we also assess the CPU, memory and power requirements involved in practical implementations of the proposed schedulers. The paper concludes that the TTC scheduler implementation using “multiple timer interrupt” (MTI) technique achieves better performance in terms of timing behavior and resource utilization as opposed to the other implementation which is based on a simple SD mechanism. Use of MTI technique is also found to provide a simple solution to “task overrun” problem which may degrade the performance of many TTC systems.

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The authors declare no conflicts of interest.

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M. Nahas, "Employing Two ‘Sandwich Delay’ Mechanisms to Enhance Predictability of Embedded Systems Which Use Time-Triggered Co-Operative Architectures," Journal of Software Engineering and Applications, Vol. 4 No. 7, 2011, pp. 417-425. doi: 10.4236/jsea.2011.47048.


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