Presentation on theme: "A Sample RTOS Presentation 4 Group A4: Sean Hudson, Manasi Kapadia Syeda Taib."— Presentation transcript:
A Sample RTOS Presentation 4 Group A4: Sean Hudson, Manasi Kapadia Syeda Taib
Overview What is a Real-Time System? What is a Real-Time OS (RTOS)?
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.
Real-Time System Categories Hard Real-Time Timing is critical. Missing a deadline causes a catastrophic failure.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.Timing is VERY important, but in spite of a failure, some progress can be made.
What is an RTOS? A specialized OS. Designed to meet several stringent requirements. Provides a restricted set of services to ensure these requirements.
RTOS Requirements Deterministic and Responsive User Control Reliable Fail-soft operation
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
OSE Architecture Process Handling Inter-process Communication Interrupt Handling
Inter-process Communication Signals (messages) Fast Semaphores Semaphores
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.
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.
Fast Semaphores Counting Semaphore. Supports wait/signal.Supports wait/signal. Faster than signals. Contain no data.Contain no data. Process specific. Only the owner can wait on this semaphore.Only the owner can wait on this semaphore. Interrupt Processes behave differently. Can not issue a wait.Can not issue a wait. Other processes can issue a signal.Other processes can issue a signal. Used to generate software events.
Semaphores Used to ensure mutual exclusion. Any process may use these semaphores.
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 InterruptsHardware Interrupts Software Events (via Wakeup Facility)Software Events (via Wakeup Facility) Timer EventsTimer Events
Interrupt Handling (cont.) Hardware Interrupts: External hardware event.External hardware event. Software Events: Triggered by an internal system call.Triggered by an internal system call. Timer Events: Depend on the system tick counter.Depend on the system tick counter. Handle recurring, fixed time requirements.Handle recurring, fixed time requirements.