Real-Time and Embedded Systems

Real-Time (RT) Systems

• Real-time systems respond to external events promptly
• Guaranteed response times
• Timely computation is needed
• Deadlines, jitters, and periodicity need to be considered
• Temporal dependency is a relevant factor
• Significance on when the outputs are produced, within specified bounds or deadlines
• Correctness relies on output values and the time inputs are processed and outputs are produced
• Hard Real-Time systems produce outputs within specified deadlines; failure results in system failure
  • Examples include Flight Control, Air Traffic Control, Robots, and Automotive Control Systems
• Soft Real-Time systems deadlines can be occasionally missed
  • Examples include communications using timeout protocols, ATMs, Airline Reservation Systems, and Process Control Systems designed to tolerate delays

Embedded Systems (ES)

• Embedded systems feature software embedded in computer hardware, dedicated to specific applications or parts of larger systems
• Specifically purposed software in computer hardware
• Any device with a programmable computer not intended as a general-purpose computer

Embedded Systems

• Embedded systems consist of hardware (processor, memory, I/O, bus) and software (OS, libraries, application, GUI)
• Hardware and software are developed through a design process using toolchains (analysis, compiler, debugging, integration)
• Embedded systems are everywhere
• In 1999, the estimation was 40-50 embedded processors per home
• Involve hardware (chips) and software (programs)
• CPU processors include ARM, PowerPC, Xscale/SA, and 68K
• Memory typically has 256MB or more
• Input/output interfaces use parallel and serial ports

Real-Time Embedded Systems (RTES)

• Relationship between real-time and embedded systems can be visualized as two intersecting circles

Requirements for RTES

• Size, Power (heat), weight, radiation-hardened for environmental considerations
• Responsive and predictable performance (fast)
• Low cost and time-to-market for economic viability
• Safety, faulty-tolerance, and security for consequence management
• Smaller, cheaper, better, and faster

Characteristics of Embedded Systems

• Reactive and real-time systems react to changes in the environment and compute results in real time without delay
• A car employs embedded systems for many tasks
  • Driving Gears
  • Windows
  • Temperature
  • Door-lock/ Theft-lock-alarm
  • Brakes/ Accelerator
  • Air-Bag, Accident/ Emergency
• Critical tasks Steering and breaking
• Non-critical tasks - Turning on a radio
• Consider the cost of fulfilling the mission for an efficient solution
• Reliability of the driver Fault-tolerance needs to be considered
• Illustrate the embedded system characteristics
• Single function repeatedly
• A system always acts as a digital camera
• Tightly constrained.
• Must be low cost

Embedded System Components

• Constraints are met with hardware/software codesign
• The codesign involves simultaneous design
• Hardware components include Processor
  • ARM
  • Memory
  • Peripherals

Software Components (Embedded Operating System)

• Essential features and considerations of real-time
• Highly configurable
  • Embedded OSs are tailored to specific hardware/application requirements by adjusting features and removing unnecessary functions
  • Typically optimized at the linker level or through advanced compile-time evaluations
• Dynamic data can be replaced with static data
  • Reduces memory management overhead and improves efficiency
• Large range of devices
• Requires diverse peripherals efficiently
• Embedded systems operate in a controlled environment with a certain purpose
  • This helps lower the need for extensive protection mechanisms
• Embedded OSs consist of specialized software components
  • Manages hardware resources, schedules tasks, handles I/O operations, and provides real-time capabilities

Examples of Embedded Operating Systems

• ARM architecture-supported operating systems include Android, Linux, Microsoft Windows System, and Symbian
• Android A Linux-based operating system for mobile devices developed by the Open Handset Alliance and Google
• Linux Started in 1991 by Linus Torvalds; now a full-featured UNIX-like operating system
• Microsoft Windows System
• Embedded systems - Windows CE and Windows XP Embedded.
• Windows CE - Minimalistic systems
• Windows XP Embedded Modularize variant of Microsoft Windows XP Professional.
• Symbian OS is the successor of 32-bit EPOC Platform from Psion
• Symbian owned by
  • Ericsson (15.6%)
  • Nokia (47.9%)
  • Panasonic (10.5%)
  • Samsung (4.5%)
  • Siemens AG (8.4%)
  • Sony Ericsson (13.1%)
• All are manufacturers of mobile phones

Hardware Overview

• ARM Processer is an efficient processor
• Builds on very successful Cortex-M0 processor
• Retaining full instruction set tool compatibility
• Reduce and increasing performance