Chapter6 RTOS Intro

Chapter6 RTOS Intro - Processes and Operating Systems(Text...

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Processes and Operating Systems (Text: Chapter 6) Multiple tasks and multiple processes. Resource management Scheduling Interprocess communication Performance Preemptive real-time operating systems (RTOSs) Book examples based on FreeRTOS.org kernel Processes and UML.
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Reactive systems © 2008 Wayne Wolf Overheads for Computers as Components 2 nd ed. Respond to external events. Engine controller. Seat belt monitor. Requires real-time response. System architecture. Program implementation. May require a chain reaction among multiple processors.
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Tasks and processes © 2008 Wayne Wolf Overheads for Computers as Components 2 nd ed. A task is a functional description of a connected set of operations. (Task can also mean a collection of processes.) A process is a unique execution of a program. Several copies of a program may run simultaneously or at different times. A process has its own state: registers; memory. The operating system manages processes.
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Why multiple processes? Processes help us manage timing complexity: multiple & variable data/execution rates multimedia (compressed vs uncompressed) automotive systems asynchronous input user interfaces - activated at random times (buttons, etc.) communication systems Process may have required period/rate periods/rates differ between processes depending on computational needs and deadlines
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Example: engine control Tasks: spark control crankshaft sensing fuel/air mixture oxygen sensor Kalman filter state machine gas pedal engine controller
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Typical rates in engine controllers © 2008 Wayne Wolf Overheads for Computers as Components 2 ed. Variable Full range time (ms) Update period (ms) Engine spark timing 300 2 Throttle 40 2 Air flow 30 4 Battery voltage 80 4 Fuel flow 250 10 Recycled exhaust gas 500 25 Status switches 100 20 Air temperature Seconds 400 Barometric pressure Seconds 1000 Spark (dwell) 10 1 Fuel adjustment 80 8 Carburetor 500 25 Mode actuators 100 100
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Life without processes Code turns into a mess: interruptions of one task for another spaghetti code time A B C A C A_code(); B_code(); if (C) C_code(); A_code(); switch (x) { case C: C(); case D: D(); ...
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Real-time systems © 2008 Wayne Wolf Overheads for Computers as Components 2 nd ed. Perform a computation to conform to external timing constraints. Deadline frequency: Periodic . Aperiodic . Deadline type: Hard : failure to meet deadline causes system failure. Soft : failure to meet deadline causes degraded response.
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This note was uploaded on 09/23/2011 for the course ELEC 6260 taught by Professor Nelson,v during the Summer '08 term at Auburn University.

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Chapter6 RTOS Intro - Processes and Operating Systems(Text...

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