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  • 1. T S PRADEEPKUMAR
    SCS, VIT University
    OSEK/VDXAReal Time Operating System
  • 2. Automotive Software Standards
    Introduction to OSEK/VDX
    OSEK/VDX Characteristics and Specification
    OSEK Architecture
    Conformance Classes (CC)
    Tasks Concepts
    Interrupts Processing
    Events
    Scheduling Policies
    Other OS Services
    Topics for discussion
  • 3. Automotive Software Standard
    • AUTOSAR
    • 4. Automotive Open System Architecture
    • 5. OSEK/VDX
    • 6. Open systems and the corresponding interfaces for automotive electronics / Vehicle Distributed eXecutive
    • 7. MISRA C
    • 8. Motor Industries Software Reliability Association
  • OSEK/VDX Characteristics
    • Scalability
    • 9. Used for wide range of control units for 8bit to 32 bit controllers
    • 10. Uses four conformance classes that specifies the main features
    • 11. Portability of software
    • 12. ISO/ANSI-C Standard interface between the application and the OS
    • 13. Configurability
    • 14. Standard configurable information is provided with the help of OIL (OSEK Implementation Language)
    • 15. Statically allocated OS
    • 16. To simplify, The OS, application tasks, resources and services are requested to define at the compile time
  • OSEK/VDX Specification
    • Three Processing Levels
    • 17. Interrupt Level
    • 18. A logical level for OS Activities
    • 19. Task Level
    The interrupt levels are assigned higher priorities than the task levels
    • In addition
    • 20. OS Services provided for task management, event management, resource, counter, alarm and error treatment
  • OSEK/VDX Specification
  • 21. OSEK/VDX Architecture
  • 22. OSEK COM
    • The OSEK standard comprises also an agreement on interfaces and protocols for in-vehicle communication called OSEK COM
    • 23. An Interaction layer which provides communication services for the transfer of application messages.
    • 24. A Network layer which provides services for the unacknowledged and segmented transfer of application messages
    • 25. A Data link layer interface which provides services for the unacknowledged transfer of individual data packets over a network to the layers above.
  • OSEK NW
    • Very often electronic control units (ECU) made by different manufacturers are networked within vehicles by serial data communication links.
    • 26. For this reason the standard propose a Network Management system (OSEK NM) that provides standardized features which ensure the functionality of inter-networking by interfaces.
  • OSEK/VDX Architecture
    • Traditional Fixed Priority Approach
    • 27. Each task in the system may be
    • 28. Basic Task (BT)
    • 29. Extended Task (ET)
    • 30. Each Task will be assigned a fixed Priority (assigned at compile time)
  • OSEK/VDX Architecture
    • Conformance Classes
    • 31. To provide support for different features and requirements of the application in terms of number of tasks, memory consumption, etc
    • 32. BCC1
    • 33. Only basic tasks limited to one activation request per task and one task per priority, while all tasks have different priorities.
    • 34. BCC2
    • 35. Like BCC1, plus more than one activation request per task and more than one task per priority.
    • 36. ECC1
    • 37. Like BCC1, plus extended tasks.
    • 38. ECC2
    • 39. Like ECC1, plus more than one task per priority and multiple requesting of task activation allowed for basic tasks.
  • Conformance Classes
  • 40. Tasks Concepts
    • Basic Task
    • 41. Basic tasks only release the processor, if
    • 42. they terminate
    • 43. the OSEK operating system switches to a higher-priority task, or interrupt occurs which cause the processor to switch to an interrupt service routine (ISR).
    • 44. Extended Tasks
    • 45. In contrast to basic tasks extended tasks are allowed to use the operating system call WaitEvent, which may result in a waiting state
    • 46. The waiting state allows the processor to be released and to be reassigned to a lower-priority task without the need to terminate the running extended task
    • 47. In view of the operating system, management of extended tasks is, in principle, more complex than management of basic tasks and requires more system resources
  • Tasks Concepts
  • 48. Tasks Concepts
    • Extended Tasks have four task states:
    • 49. Running
    • 50. Only one task can be in this state at any point in time
    • 51. Ready
    • 52. The scheduler decides which ready task is executed next
    • 53. Waiting
    • 54. A task cannot continue execution because it has to wait for at least one event
    • 55. Suspended
    • 56. The task is passive and can be activated
  • Interrupt Processing
    In particular, the standard provides two kind of ISR handlers:
    • ISR Category 1
    • 57. ISR does not use an OS Service.
    • 58. No OS calls from the handler
    • 59. The designer is free to write his own handler
    • 60. These are the faster highest priority Interrupt
    • 61. ISR Category 2
    • 62. ISR is handled by the OS
    • 63. So OS calls can be called from the handler
  • Events
    • Event Mechanism is provided only for Extended Tasks
    • 64. Each (ET) owns a set of events that can be triggered by other BT or ET or even ISR Category 2
    • 65. The behavior of an ET is to wait for an Asynchronous Event calling the OS Service WaitEvent()
    • 66. Events can be set only if the task is not in the suspended state
  • Scheduling Policy
    • Mixed Preemptive Scheduling
    • 67. Non Preemptive scheduling
  • Scheduling Policy
    • Mixed Preemptive Scheduling
    • 68. Since preemptiveness is a task attribute, preemptive and non-preemptive tasks can be mixed in the same application.
    • 69. The running task will influence the policy really used.
  • Other OS Services