Introduction to embedded Systems

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Introduction to embedded Systems
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Outline

• Embedded systems overview
• What are they?
• Design challenge optimizing design metrics
• Technologies
• Processor technologies
• IC technologies
• Design technologies

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Embedded systems overview

• Computing systems are everywhere
• Most of us think of desktop computers
• PCs
• Laptops
• Mainframes
• Servers
• But theres another type of computing system
• Far more common...

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Embedded systems overview

• Embedded computing systems
• Computing systems embedded within electronic
  devices
• Hard to define. Nearly any computing system other
  than a desktop computer
• Billions of units produced yearly, versus
  millions of desktop units
• Perhaps 50 per household and per automobile

Computers are in here...
and here...
and even here...
Lots more of these, though they cost a lot less
each.
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A short list of embedded systems
Anti-lock brakes Auto-focus cameras Automatic
teller machines Automatic toll systems Automatic
transmission Avionic systems Battery
chargers Camcorders Cell phones Cell-phone base
stations Cordless phones Cruise control Curbside
check-in systems Digital cameras Disk
drives Electronic card readers Electronic
instruments Electronic toys/games Factory
control Fax machines Fingerprint identifiers Home
security systems Life-support systems Medical
testing systems
Modems MPEG decoders Network cards Network
switches/routers On-board navigation Pagers Photoc
opiers Point-of-sale systems Portable video
games Printers Satellite phones Scanners Smart
ovens/dishwashers Speech recognizers Stereo
systems Teleconferencing systems Televisions Tempe
rature controllers Theft tracking systems TV
set-top boxes VCRs, DVD players Video game
consoles Video phones Washers and dryers

• And the list goes on and on

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Automotive embedded systems

• Todays high-end automobile may have 100
  microprocessors
• 4-bit microcontroller checks seat belt
• microcontrollers run dashboard devices
• 16/32-bit microprocessor controls engine.

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BMW 850i brake and stability control system

• Anti-lock brake system (ABS) pumps brakes to
  reduce skidding.
• Automatic stability control (ASCT) controls
  engine to improve stability.
• ABS and ASCT communicate.
• ABS was introduced first---needed to interface to
  existing ABS module.

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BMW 850i, contd.
sensor
sensor
brake
brake
hydraulic pump
ABS
brake
brake
sensor
sensor
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Some common characteristics of embedded systems

• Single-functioned
• Executes a single program, repeatedly
• Tightly-constrained
• Low cost, low power, small, fast, etc.
• Reactive and real-time
• Continually reacts to changes in the systems
  environment
• Must compute certain results in real-time without
  delay

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• Supported by a wide array of processors
• Cost sensitive
• Uses real-time operating systems(RTOS)
• Must operate under extreme environmental
  conditions
• Fewer system resources
• Object code stored in ROM
• Software failure is much more severe

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Cost Sensitivity

• Usually embedded systems are manufactured in bulk
• Limited functionality(Size,Power,price)
• Powerful embedded processors
• Above requirements are found in cellular
  phones(DSP processors)

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Extreme Environmental conditions

• Runs everywhere anytime under any condition
• It is not good practice to consider following
  aspects during testing or packaging
• Heat budget
• Slow down the clock
• Change code(Optimize)

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Real-Time constraints

• Time sensitive constraints(Soft real-time)
• Due to some technical limitations task
  will take longer time than the design goal.
  Instead of printing three pages per minute, two
  pages are printed.
• Time critical(Hard real-time)
• Time critical task should take place
  within a time frame, available between monitored
  or measured events. If the task is not completed
  before the next event arrives, the function
  controlled by that task fails.

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An embedded system example -- a digital camera

• Single-functioned -- always a digital camera
• Tightly-constrained -- Low cost, low power,
  small, fast
• Reactive and real-time -- only to a small extent

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Design challenge optimizing design metrics

• Obvious design goal
• Construct an implementation with desired
  functionality
• Key design challenge
• Simultaneously optimize numerous design metrics
• Design metric
• A measurable feature of a systems
  implementation
• Optimizing design metrics is a key challenge

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Design challenge optimizing design metrics

• Common metrics
• Unit cost the monetary cost of manufacturing
  each copy of the system, excluding NRE cost
• NRE cost (Non-Recurring Engineering cost) The
  one-time monetary cost of designing the system
• Size the physical space required by the system
• Performance the execution time or throughput of
  the system
• Power the amount of power consumed by the system
• Flexibility the ability to change the
  functionality of the system without incurring
  heavy NRE cost

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Design challenge optimizing design metrics

• Common metrics (continued)
• Time-to-prototype the time needed to build a
  working version of the system
• Time-to-market the time required to develop a
  system to the point that it can be released and
  sold to customers
• Maintainability the ability to modify the system
  after its initial release
• Correctness, safety, many more

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Microprocessor varieties

• Microcontroller includes I/O devices, on-board
  memory.
• Digital signal processor (DSP) microprocessor
  optimized for digital signal processing.
• Typical embedded word sizes 8-bit, 16-bit,
  32-bit.

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Application examples

• Simple control front panel of microwave oven,
  etc.
• Canon EOS 3 has three microprocessors.
• 32-bit RISC CPU runs autofocus and eye control
  systems.
• Analog TV channel selection, etc.
• Digital TV programmable CPUs hardwired logic.

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Decade Predominant Technology
60s Mainframes
70s Mini Computers
80s Personal Computers
90s Internet for people
2000 Internet for Devices
and beyond
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Summary

• Embedded systems are everywhere
• Key challenge optimization of design metrics
• Design metrics compete with one another
• A unified view of hardware and software is
  necessary to improve productivity
• Three key technologies
• Processor general-purpose, application-specific,
  single-purpose
• IC Full-custom, semi-custom, PLD
• Design Compilation/synthesis, libraries/IP,
  test/verification