1.%20What%20are%20embedded%20systems?

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• 2004/02/10

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1. What are embedded systems?

• Definition
• Embedded system any device that includes a
  programmable computer but is not itself a
  general-purpose computer.
• Take advantage of application characteristics to
  optimize the design
• dont need all the general-purpose bells and
  whistles.

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A More Detailed Definition

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Embedding a computer
output
analog
input
CPU
analog
mem
embedded computer
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Examples

• Personal digital assistant (PDA).
• Printer.
• Cell phone.
• Automobile engine, brakes, dash, etc.
• Television.
• Household appliances.
• PC keyboard (scans keys).

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Reference Interpretation (1)

• An "embedded system" is any computer system or
  computing device that performs a dedicated
  function or is designed for use with a specific
  embedded software application.
• Embedded systems may use a ROM-based operating
  system or they may use a disk-based system, like
  a PC. But an embedded system is not usable as a
  commercially viable substitute for general
  purpose computers or devices.

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Reference Interpretation (2)

• A specialized computer system that is part of a
  larger system or machine. Typically, an embedded
  system is housed on a single microprocessor board
  with the programs stored in ROM. Virtually all
  appliances that have a digital interface --
  watches, microwaves, VCRs, cars -- utilize
  embedded systems. Some embedded systems include
  an operating system, but many are so specialized
  that the entire logic can be implemented as a
  single program.

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Reference Interpretation(3)

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1.2 ??????????

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• 1971?Intel 4004, 4?????
• TI, TMS1000, 4?????
• ROM, RAM, CPU I/O port
• 1980?Intel MCS-51, 8?????
• 16?, 32?????
• 1990s, DSP
• TMS320C30

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????????????(1)

• ????(MCUMicro-Controller Unit)
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• Intel 8051
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• ARM??,MIPS

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????????????(2)

• ???????(DSP Digital Signal Processor)
• ??????????????,???????DSP??,??????,?????????
• TI TMS320C30
• -gt????(System-on-Chip, SoC)
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• Intel PCA??PXA 255

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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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????????

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• 1981, ??????? VTRX32
• 1990s, QNX-4
• pSOS, VxWorks, Palm OS, WinCE, Embedded Linux,
  LynxOS, uCOS, Nucleus

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• 32???????
• 32?DSP????
• SoC
• SoPC

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IA Embedded System

• Information Appliance
• An appliance specializing in information
  Knowledge, facts, graphics, images, video, or
  sound. An information appliance is designed to
  perform activity, such as music, photography, or
  writing. A distinguishing feature of information
  appliance is the ability to share information
  among themselves. (Don Norman)

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IA Embedded System (contd)

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?????????

• ????(MPU)
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• ???????(DSP)
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• ROM
• PROM,EPROM,EEPROM
• Flash ROM
• Flash????????????(boot ROM?hard disk)
• RAM
• SRAM
• DRAM

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PXA255 Architecture
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VxWorks Architecture
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Embedded Linux

• Basic components
• Boot loader
• Linux kernel
• Further
• Hardware drivers
• Application programs
• File systems based on ROM or RAM
• TCP/IP stack
• GUI

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Characteristics of embedded systems

• Sophisticated functionality.
• Real-time operation.
• Low manufacturing cost.
• Low power.
• Designed to tight deadlines by small teams.

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Functional complexity

• Often have to run sophisticated algorithms or
  multiple algorithms.
• Cell phone, laser printer.
• Often provide sophisticated user interfaces.

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Real-time operation

• Must finish operations by deadlines.
• Hard real time missing deadline causes failure.
• Soft real time missing deadline results in
  degraded performance.
• Many systems are multi-rate must handle
  operations at widely varying rates.

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Non-functional requirements

• Many embedded systems are mass-market items that
  must have low manufacturing costs.
• Limited memory, microprocessor power, etc.
• Power consumption is critical in battery-powered
  devices.
• Excessive power consumption increases system cost
  even in wall-powered devices.

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Design teams

• Often designed by a small team of designers.
• Often must meet tight deadlines.
• 6 month market window is common.
• Cant miss back-to-school window for calculator.

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??????????

• LED
• Simulator
• ICE (In-Circuit Emulator)
• ??JTAG?Embedded ICE
• Angel

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Simulator

• Simulator (???)
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ICE

• ICE In-Circuit Emulator
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• ICE????????,???????CPU???????ICE?????CPU????????,?
  ????????CPU??????????,?????CPU?????????????
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  ???????????

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Embedded ICE

• Embedded ICE ???????
• IBCR (Instruction Break Control Register)
• DBAR (Data Break Address Register)
• JTAG??
• JTAG(Joint Test Action Group) ?????????,??5???????
  ?????????
• ARM?????????????????,?JTAG????????????,???????????
  ???,ARM????????????????,????????????????????

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Angel

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• Debug??????PC???????,????????????????,????????????
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• ??Angel????ADP(Angel Debug Protocol),????PC???????
  ???????,?????????????
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  ?????
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ARM?????
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Embedded System Design

• Top-down design
• start from most abstract description
• work to most detailed.
• Bottom-up design
• work from small components to big system.
• Real design uses both techniques.

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Levels of abstraction
requirements
specification
architecture
component design
system integration
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Example GPS moving map

• Requirements
• Specification
• Architecture
• Component design
• System integration

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Review