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DEV PATEL-IU1941090008-Interrupt Handling in RTOS.pptx
- 1. Interrupt Handling in RTOS DEV PATEL EC 7th Sem
- 2. Interrupt handling is a key function in real-time software, and comprises interrupts and their handlers. Only those physical interrupts which of high enough priority can be centered into system interrupt table. The software assigns each interrupt to a handler in the interrupt table. An interrupt handler is just a routine containing a sequence of operations. Each of these may request input and output while running.
- 3. As soon as several tasks run in a program, it is virtually impossible to achieve good response times by polling (continuous enquiry of an event). Continuous polling would prevent tasks with lower priorities from running and thus waste precious CPU time. Therefore, it should always be attempted to replace polling by interrupts. This leads to the best response times and optimal use of the hardware available. RTKernel-32 uses the timer interrupt to activate tasks waiting for a certain point in time. Module RTCom provide interrupt support for serial ports. This section discusses how to implement a handler for any interrupt source. An interrupt handler may be thought of as a task running with a priority higher than all other tasks. However, there are some important considerations to keep in mind.
- 4. While an interrupt handler is active, no other interrupts with lower priorities can be processed. Therefore, it is important to minimize the execution times of interrupt handlers, because otherwise the interrupt response time for other interrupts might suffer. The handler should avoid any processing not immediately required and delegate it to a task.
- 5. An interrupt handler may: declare and use local variables, call other functions, call functions RTKSignal or RTKWaitCond to activate other tasks, call the conditional mailbox and message passing operations (RTKPutCond, RTKGetCond, RTKSendCond, RTKReceiveCond) to exchange data with tasks. An interrupt handler must not: use the coprocessor or emulator without saving/restoring its state, use more than 512 bytes of stack (the less, the better), cause blocking task switches.
- 6. RTOS calling the corresponding ISR, the ISR sending messages to priority queue of Interrupt Service threads
- 7. Direct Call to an ISR and ISR Enter message On an interrupt, the process running at the CPU is interrupted ISR corresponding to that source starts executing. A hardware source calls an ISR directly. The ISR just sends an ISR enter message to the RTOS. ISR enter message is to inform the RTOS that an ISR has taken control of the CPU