**13. Acknowledgement**

We express our sincere gratitude to the Dean's Office of The Graduate School at The University of Alabama for supporting the underlying infrastructure of servers, development tools and the systems development track history records.

### **14. References**


**0**

**3**

<sup>1</sup>*Chaminade University*

<sup>3</sup>*PUC Minas*

<sup>1</sup>*USA* 2,3*Brazil*

**Schedulability Analysis of Mode**

**Changes with Arbitrary Deadlines**

Timóteo2, R. Moraes2, E. Ursini2 and Udo Fritzke Jr3

<sup>2</sup>*Universidade Estadual de Campinas (UNICAMP)*

Paulo Martins1,2, I. G. Hidalgo2, M. A. Carvalho2, A. de Angelis2, V.

Modern real-time systems are required to operate in complex applications and dynamically adapt to a wide range of changes in the environment. One strategy that allows the implementation of these systems in complex scenarios is the partitioning of their applications into modes of operation. Flexibility of operation is achieved by having the system execute in several modes of operation and undergo transitions between modes in response to external or internal events. A mode of operation can be seen as a specific configuration of the computational resources that is optimal for the operational phase that the system executes. As conditions in the environment change, resource allocations may become inadequate. Therefore, the system must reconfigure itself through a mode change, reallocating its resources in an efficient manner. A classic example of modes lies in the area of aviation where most aircraft undergo at least three basic modes of operation: take-off, level-flight, and landing modes. Having the system designed with a single mode of operation does not explore the fact that some operations, and thus resource usage, are mutually exclusive. The allocation of all these resources, as if they could be needed at the same time, leads to inefficiency. More importantly, the resulting system is not scalable. The so called "*all-modes-in-one*" system is

Flexible modal real-time systems must guarantee by means of schedulability analysis that all tasks complete before their deadlines. Current literature in schedulability analysis for mode changes requires that all task deadlines are less than or equal to the tasks periods (Pedro & Burns, 1998; Real & Crespo, 2004). Allowing task deadlines to be less than task periods is useful for many real-time applications (Tindell et al., 1994). However, in some real-time applications an instance of a task is allowed to arrive before its previous invocation has finished. In such case the task can be delayed until its previous invocation terminates.

This chapter extends the current schedulability analysis associated with mode changes in static priority pre-emptive based scheduling. In particular, it derives analysis that includes

usually feasible for simple systems with limited functionality.

**1. Introduction**

