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Chapter 1

Chapter 1. Embedded And Real-Time System Department of Computer Science Hsu Hao Chen Professor Hsung-Pin Chang. Outline. What is an embedded system ？ Characteristics of embedded systems Real-time systems concept Real-time operating systems and real-time kernels

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Chapter 1

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  1. Chapter 1 Embedded And Real-Time System Department of Computer Science Hsu Hao Chen Professor Hsung-Pin Chang

  2. Outline • What is an embedded system？ • Characteristics of embedded systems • Real-time systems concept • Real-time operating systems and real-time kernels • Processes, tasks, and threads • Architecture of real-time systems

  3. What is an embedded system？ • For practical purposes • Embedded system consisting of a compact, fast, and extremely reliable operating system • Microprocessor located inside a device • Embedded system is a collection of programs that run under operating system

  4. Characteristics of embedded systems(1/2) • Virtually all kinds of computing systems • Temporal determinism • Time required to process any task is finite and predictable • Less concerned with average response time than worst-case response time • Must have a guarantee on the upper time limit

  5. Characteristics of embedded systems(2/2) • It is typically encapsulated by the hardware it controls, so end-users are unaware of its presence • It is actually a computer system that does not have the outward appearances of a computer system.

  6. Real-time systems concept • Operate within specified time constraints • System must respond to inputs or events within prescribed time limits • Real-time constraints: • Hard Real-Time • Example: air traffic control system. • Soft Real-Time • Example: PS2

  7. Real-time operating systems and real-time kernels RTOS kernel Other RTOS services Kernel

  8. Processes, tasks, and threads

  9. Architecture of real-time systems(1/2) • Threads are process two common architecture • Control loop with polling • Polling of the kernel executes an infinited loop Advantage: easy to implement Disadvantage: difficult to give threads with critical fast access to the processor

  10. Architecture of real-time systems(2/2) • Preemptive scheduling method • ThreadX use is preemptive scheduling method Advantage: priority solved critical fast access to the processor

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