Sogang University

Embedded Computer Architecture

Chap 1. Introduction

Hyuk-Jun Lee, PhD

Dept. of Computer Science and EngineeringSogang University

Seoul, Korea

Email: hyukjunl@sogang.ac.kr

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Contents

• What is Embedded System ?

• Characteristics of Embedded System

• Embedded System Components (H/W, S/W)

• Examples of Embedded Applications

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What is Embedded System ?

• Definition of an Embedded System

– An embedded system is various type of computer system or computing device that performs a dedicated function and/or is designed for use with a specific embedded software application.

– Embedded systems may be built with operating system or without operating system. An embedded system is not generally usable as a commercially viable substitute for general-purpose computers or devices.

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Characteristics of Embedded System

• Application-specific functionality

– Optimal design is possible to fit special purpose.

• Optimized for various metrics

– Performance, e.g. throughput, worst case execution time

– Cost

– Power/energy consumption

– Reliability, e.g. extremely harsh environment, safety critical

– Limited size or resources

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Components (H/W)

• Embedded System H/W

– Processor : handling program instructions

– Memory : saves program and data

– Peripheral device : connecting system and external devices

– Network device

• PC H/W vs. Embedded System H/W

H/W PC Embedded System

Processor High-performance High to low performance

Memory Big capacity High to low capacity

Auxiliary storage Variety : HDD, ODD, DVD, etc.

Sometimes

Peripheral device Variety : Keyboard, Mouse, Speaker, etc.

Under the necessity

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Components (H/W)

• Processor

– Perform execution of programs

– Speed

• hundreds of MHz to GHz clock rate

• 8 bits, 16 bits, 32 bits and 64 bits

– depend on data bus size and basis operation unit

– PC

• Intel, AMD, NVidia

– Embedded System

• ARM, MIPS, Motorola, TI, Samsung, Qualcomm, Apple, Google etc

• Varies based on function complexity as well as system size

• Micro-processor : includes only CPU core (data and control section)

• Micro-controller : includes CPU core, various types/sizes memory

and various peripheral devices

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Components (H/W)

• Memory/Storage

– Main role : saving programs and data

– RAM : Volatile memory

• Used primarily to save large program or data.

• DRAM (Dynamic Random Access Memory)

– Commonly large capacity

– tens of nanoseconds access time

• SRAM (Static Random Access Memory)

– Commonly small capacity

– High speed : Cache memory, place for deterministic memory access

– Sub-nano or a few nanoseconds access time

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Components (H/W)

– Flash Memory : Non-volatile memory

• Read, write (program) or erase operations

• Flash memory is cheap compared to the byte-programmable

EEPROM, but only can erase/write a block at a time.

• Offer faster read/write access time (not as fast as volatile DRAM)

and better shock resistance than hard disks.

– Tens of microseconds for read, Hundreds of microseconds for write, a few

milliseconds for erase

• Gain popularity in portable electronic devices and replace EEPROMs,

and HDD

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Components (H/W)

• I/O devices– Respond to external input, and perform its task.

– Two ways of accessing

• Polling : simple implementations

• Interrupt : efficient implementations

– Input devices

• Keyboard, Mouse, Microphone, Sensor, touchpad etc.

– To convert analog signals to digital information

• Analog signal : analog sensor (ex) temperature

• Need ADC (Analog to Digital Converter).

ex) temperature changing → output temperature (analog sensor)

→ digital signal (ADC) → control program → output to heater

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Components (H/W)

– Output devices

• LED : output signal on/off

• 7-segment : number or alphabet

• LCD : picture, etc.

• Serial port

– RS232C standard

– Connect peripheral device in several meters

– Low speed, simple

• Parallel port

– For close place than serial interface

• Printer interface (speed : about 20KB/sec)

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Components (H/W)

• USB (Universal Serial Bus) / IEEE 1394

– Faster than others

– USB 3.0

• Popular in many devices

• The maximum transfer rate is ~5Gbps

• Printer, scanner, keyboard, joystick, MP3 player, TV etc.

– IEEE 1394 (Firewire by Apple)

• The maximum transfer rate is 400Mbps~3.2 Gbps.

• HDD, CD/CD-RW, video camera, etc.

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Components (H/W)

• Network device

– Control peripheral device far away

– Cable network

• Ethernet

• IEEE 802.3 standard

– Wireless network

• IEEE 802.11 standard (a/b/g/n) - WiFi

• Bluetooth – personal area network(PAN), low power, low BW

• Zigbee - PAN, low power, low BW

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• Sensors

– CCD or CMOS camera sensor

– Haptic/tactile sensor

– Gyro sensor (gyroscope)http://www.youtube.com/watch?v=cquvA_IpEsA

Components (H/W)

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Components (S/W)

• Embedded System S/W

– OS : RTOS (Real-time Operating System),

Embedded Linux

– System S/W : OS API, Network API, etc.

– Application S/W

• PC S/W vs. Embedded System S/W

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Examples of Embedded Applications

• Consumer

– 3D HDTV, Game box

– Home appliances

– Entertainment (Audio/Video)

• Communication

– Smart phone, mobile phone

– Telephone, Answering machines

– Networking (Ethernet, IP routing)

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• Automotive

– Engine Control Unit, Transmission Control Unit

– Power windows, seats

– Safety (airbag, ABS)

– Navigation

Examples of Embedded Applications

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• Military

– Target recognition

– Guidance

– Navigation

• Industrial

– Traffic Control

– Robotics, Production

– Inventory, Stock management

Examples of Embedded Applications

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• Medical

– MRI, CT, Ultrasonic

– Pacer

– Wireless implant

Examples of Embedded Applications

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Tentative Course Outline

• Processor architecture– Review on computer architecture– Metrics and ISA– Instruction level parallelism– ARM processor architecture and code optimization– GPGPU

• Memory System– Basic and advanced cache architecture– Memory systems and virtual memory

• IO devices and operations• Examples for embedded systems

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Teaching Materials

• Main

– Lecture slides

• References

– D.A. Patterson and J.L. Hennessy, Computer Organization and

Design: The Hardware/Software Interface, 4th edition, Morgan

Kaufmann, 2008.

– J.L. Hennessy and D.A. Patterson, Computer Architecture: A

Quantitative Approach, 4th edition, Morgan Kaufmann, 2006.

– ARM System Developer’s Guide, A. Sloss, D. Symes, and C.

Wright, Morgan Kaufmann,2004