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Real Time Operating System


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  • Transcript

      EC VI B
    • 2. Operating System
      • Collection of system calls (functions)
      Provides a set of basic services to interact with the hardware
      • Core of the OS is Kernel
      Basic structural unit of OS
      Typically a library or set of libraries
      A bridge between applications and the actual data processing done
      at the hardware level
    • 3. Basic Structure of Operating System
    • 4. Real Time Operating System
      • Completes its task and deliver services on time
      • 5. Deterministic – guarantees task completion at a set deadline
      • 6. Operates in constrained environment where computer memory and processing power is limited
      • 7. Provides services in definite amount of time
      • 8. Multitasking or multi-threading
    • Features
      • Fast
      • 9. Small and occupy very little memory
      • 10. Consume fewer resources
      • 11. Mission-critical
      • 12. Response times are highly predictable
      • 13. Unpredictable environment
      • 14. Life risking applications
    • Applications of RTOS
      • Air Traffic Control Systems
      • 15. Networked Multimedia Systems
      • 16. Command Control Systems
      • 17. Internet Telephony
      • 18. Anti-lock Brake Systems
      • 19. Heart Pacemaker
    • Types of RTOS
      • Hard Real-Time Systems
      Meets deadlines with zero degree of flexibility
      Missed deadlines cause catastrophe
      Cost of catastrophe is high
      • Soft Real-Time Systems
      Meets deadlines with some degree of flexibility
      Missed deadline does not cause catastrophe
      Costs rise in proportion to the delay
    • 20. Example of Hard Real-Time Systems
      • Weapons defense system
      • 21. Missile guidance system
      Weapons Defense System
    • 22. Example of Soft Real-Time Systems
      • Networked Multimedia System
      • 23. DVD or multimedia players
      • 24. Internet telephony
    • 25. Tasks
      • Group of instructions performing a function of a system
      • 26. An independent thread of execution
      • 27. It is schedulable
      • 28. Characterized by associated name, unique ID, priority, task control block (TCB), stack & taskroutine
      • 29. Each task moves from one state to another using finite state machine (FSM)
    • Task States
      • Executing Actually running
      • 30. Ready Ready to be dispatched
      • 31. Blocked Blocked by another task or resource
      • 32. Waiting Blocked by time
    • Scheduler
      • Maintains ranked list of tasks based on priority
      • 33. Makes sure that all tasks meet their timing constraints
      • 34. It is not a task but a function call [schedule()]
      • 35. Called at various scheduling points likewise end of ISR, when tasks go to sleep or when they are ready to run
      • 36. Types of algorithms
      Preemptive priority based scheduling algorithm
      Round Robin scheduling algorithm
    • 37. Preemptive priority based scheduling algorithm
      • Each task has a priority and highest-priority task runs first
    • Round Robin scheduling algorithm
      • Each task of same priority uses time slice to achieve equal share of CPU execution time
    • Semaphores
      • A kernel object that one or more threads of execution can acquire or release for the purposes of synchronization or mutual exclusion.
      • 38. Acts like a key
      • 39. Allows a task to carry out some operation or to access a resource
      • 40. Types
      Binary Semaphore
      Counting Semaphore
      Mutual Exclusion Semaphore
    • 41. Semaphores (Contd.)
      • Binary Semaphore
      • 42. Counting Semaphore
      • 43. Mutual Exclusion Semaphore
    • Message Queues
      • It is like a pipeline through which tasks & ISRs communicate and synchronize with data.
      • Non-interlinked
      one-way data communication
      • Interlocked
      one-way data communication
      • Interlocked
      two-way data communication
      • Broadcast Communication
      Ways to use Message Queues
    • 44. Exceptions & Interrupts
      • Exception is any event that disrupts the normal execution of the processor and forces the processor into execution of special instructions
      • 45. Types
      Synchronous Exceptions Raised by internal events like processor instructions
      “An arithmetic operation that results in a division by zero”
      Asynchronous Exceptions Associated with hardware signals from external hardware devices
      Also called as INTERRUPTS
      “Pushing the reset button on the embedded board”
    • 46. I/O Subsystem
      • Hides the device-specific information from the kernel as well as from the application developer and to provide a uniform access method to the peripheral I/O devices of the system.
      • 47. Defines the standard set of functions called API.
    • Communication
      • Transfer of data from one task to another task.
      • 48. Signal the occurrences of events from one task to another task
      • 49. Control the execution of tasks by other task
      • 50. Synchronize activities
      • 51. Implement additional synchronization protocols for resource sharing
    • RTOS Distributions
    • Thank You