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Real-Time Software Design and Analysis for Embedded Systems

This research focuses on developing a methodology for designing and analyzing real-time embedded applications to ensure timely responses to external and internal constraints. It covers the characteristics, problems, and state-of-the-art in real-time system research, aiming to provide support for temporal determinism and efficient use of limited resources.

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Real-Time Software Design and Analysis for Embedded Systems

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  1. Design and Analysis of Real-Time Software REal TIme System Laboratory Scuola Superiore S.Anna G. Lipari E. Bini Ericsson Lab Italia C. Vitucci

  2. Outline • Introduction to RT embedded systems • characteristics • problems • state of the art • RT system research at Retis Lab • Goal of this research • Methodology • Phases

  3. Goal of this research • Methodology for the design and analysis of Real-Time Embedded applications to be used in all phases of development

  4. Starting Point • Real Time embedded applications • car controller • hand-held computers • cellular phone • next generation cellular phones (UMTS) • wearable computers • etc. • The target application • telecommunication control board

  5. RT embedded applications • Limited resources • memory • CPU speed • power consumption • Dedicated HW • Temporal constraints • Applications must react to external environment in a timely manner • Internal constraints (buffer size, interrupt handling, etc.)

  6. RT design and analysis • Support temporal determinism: • providing kernel-level services • priority-based schedulers • bounded delay on system calls • providing tools for off-line analysis • a tool for specification in a formal (or semi-formal) language • a tool for timing analysis • a tool for testing

  7. Application model • Application • on a single processor there are low-level control tasks (driver ATM etc.) and high-level control tasks (signaling) • need to verify the temporal constraints on every task/activity • A task can be activated • periodically (time driven) • by external events (event driven) • Tasks communicate through messages

  8. RTOS and HW • OSE Delta • currently used in Ericsson for developing software for RT embedded applications • based on a message passing communication mechanism • HW • usually, a single processor board • many different processor can be used • performance strongly depends on the HW

  9. Application model • Unit -> set of tasks HW

  10. Deadline = 150 msec HW Temporal constraints Period = 5 msec MIT = 10 msec

  11. State of the art • In the engineering practice • no a-priori timing analysis is done • low-level control tasks are directly coded in C or assembler • often, the code of high-level control tasks is automatically generated by tools that do not consider temporal constraints • temporal constraint are verified only during the testing phase

  12. State of the art • RT Analysis • RT research focused on time-driven control applications • schedulability conditions for periodic task sets • Few research papers on RT analysis of reactive (event driven) systems • Commercial tools: Time Wiz • Rate Monotonic analysis • non-std notation for specification

  13. State of the art: RT notations • Existing notations • HRT-HOOD (used in aerospace applications) • ROOM (from Object Time, now Rational Software) • Not suitable for our purposes • UML is a good candidate notation • A preliminary proposal to OMG for a standard RT extension to UML has been made in Aug. 2000 • proponents: TimeSys, I-Logix, Rational Software, etc. • http://www.omg.org/meetings/schedule/UML_Profile_for_Scheduling_RFP.html

  14. Problems • Few tools integrate specification and analysis • Time Wiz of TimeSys is one of the few • The greatest problem is to estimate the worst case computation time of every activity • strongly depends on the HW • existing tools cover a narrow range of HW configurations • There is the need for a tool that covers the entire development cycle • at design time, with a proper RT notation • after development, with a RT analysis

  15. Summary • Many different tools • for RT-analysis (Time Wiz) • for RT specification (Rational Rose RT) • for WCET analysis (VCC) • no easy-to-use off-the-shelf solution • there is the need to integrate different of technologies • specification of RT systems • RT analysis • WCET computation • etc.

  16. Research at Retis Lab • ASI project • Intecs • definition of a HRT-UML notation • enhancing UML-nice with RT-analysis • MADESS project • Parades, Magneti Marelli, ST microelectronics • RT kernel for embedded controllers with minimal memory requirements • RT kernel for multi-processor system-on-a-chip

  17. Goal of this research • A methodology for the design and analysis of RT embedded applications Code analizer Testing Specification (RT-UML) Code templates Implementation Consistency check RT analysis WCET

  18. Phases • Model of a OSE-Delta process • Mapping to the appropriate RT-UML notation • RT analysis on the model • consistency check • timing analysis • priority assignment • Integrating WCET computation

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