A Sample RTOS Presentation 4 Group A4: Sean Hudson, Manasi Kapadia Syeda Taib

1. A Sample RTOSPresentation 4Group A4:Sean Hudson, Manasi KapadiaSyeda Taib

2. Overview • What is a Real-Time System? • What is a Real-Time OS (RTOS)?

3. What is a Real-Time System? • Any system in which an operation must occur within certain fixed time constraints. • In these systems, if an operation is computationally correct and arrives late, it is considered invalid.

4. Real-Time System Categories • Hard Real-Time • Timing is critical. Missing a deadline causes a catastrophic failure. • Soft Real-Time • Timing is VERY important, but in spite of a failure, some progress can be made.

5. What is an RTOS? • A specialized OS. • Designed to meet several stringent requirements. • Provides a restricted set of services to ensure these requirements.

6. RTOS Requirements • Deterministic and Responsive • User Control • Reliable • Fail-soft operation

7. OSE • Commercially available RTOS. • Developed by ENEA OSE Systems. • Kernel is fully preemptible. • Transparent IPC among multiple processors. • Supports Advanced Memory Management features. • Supports dynamic kernel reconfiguration

8. OSE Architecture • Process Handling • Inter-process Communication • Interrupt Handling

9. Process Categories • Static • Dynamic

10. Process Types • Interrupt Processes • Timer Interrupt Processes • Prioritized Processes • Background Processes • Phantom Processes

11. Process States

12. Process Scheduling • Pre-emptive • Cyclic • Priority Based • Round Robin

13. Process Priorities • Interrupt Processes • Timer Interrupt Processes • Prioritized Processes • Background Processes

14. Inter-process Communication • Signals (messages) • Fast Semaphores • Semaphores

15. Signals • Messages between processes. • Contain sender and receiver ID’s. • Identifying the target process is crucial. • Processes can selectively receive signals. • Signals change ownership when sent.

16. Signal Redirection • Mechanism to process signals with another process. • Signals can be sent to processes on another processor. • Allows a signal interface to be defined without knowledge of a particular process hierarchy.

17. Fast Semaphores • Counting Semaphore. • Supports wait/signal. • Faster than signals. • Contain no data. • Process specific. • Only the owner can wait on this semaphore. • Interrupt Processes behave differently. • Can not issue a wait. • Other processes can issue a signal. • Used to generate software events.

18. Semaphores • Used to ensure mutual exclusion. • Any process may use these semaphores.

19. Interrupt Handling • Interrupts are special events that need to be processed ASAP. • Each interrupt is processed by an Interrupt Service Routine (ISR). • Each ISR is its own task and has a unique priority associated with it. • Methods to call an ISR: • Hardware Interrupts • Software Events (via Wakeup Facility) • Timer Events

20. Interrupt Handling (cont.) • Hardware Interrupts: • External hardware event. • Software Events: • Triggered by an internal system call. • Timer Events: • Depend on the system tick counter. • Handle recurring, fixed time requirements.

21. Summary