Introduction to Embedded Systems

Read Chapter 1

(David E. Simon, An Embedded Software Primer)

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What is an Embedded System (E.S.)?

• Embed: – Definition 1: to fix (something) firmly and

deeply (Longman Dictionary)– Definition 2: to enclose closely in a

surrounding mass (Webser Dictionary)

• System: implicitly a controlling system.

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Logical View of an Embedded System

Control System

Some Function

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Key Differences with PCs

• React to external events that may be particularly rapid– Elevator on a sky-scrapper at 7:45am or 4:55pm– Missile flying at low altitude over a mountainous

area

• Must handle unusual events– A user blocking an elevator door, power blackout,

memory failure

• Task request with deadlines

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Required Features for E.S.

• Throughput• Response• Testability• Low power• Reliability• Safety

• Maintainability• Security• Availability• Cost• Size/Weight• Survivability

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ENIAC for Smart Bombs (1948)

• Keeping the scale: the Atlas rocket would be needed to deliver a firecracker!

• Up to the 70’s, embedded systems did not make sense for general public usage

ExplosiveControlling system

170Kops30 tons200 KW

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What Made E.S. Possible ?Small and Cheap

• 1971: Intel 4004, first microprocessor (4bits), initially for a calculator.

• 1981: IBM chooses Intel 8088 for the first PC.

• Microprocessors get so cheap that microprocessor-based control systems become the rule.

• Only limit: processing time.

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Products with Embedded Systems ?• Of 4 billions microprocessors/microcontrollers sold

per year, 95% are for embedded products:– VCRs, DVD players– Cell phone– Microwave– Washer– Camera – Cars (antilock brake system, air-bag, gas injection,

electricity distribution..)– Printers, copiers– ………..

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Evolution of Embedded Systems

• Hardwired systems initially

• Microprocessor-based

• Microcontroller-based

• Specialized (application) processors

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Evolution of Embedded Systems (2)

PMemorySystem

I/O

Address Bus

Data Bus

Digital inputs (parallel input)

Microcontroller

LED

Switch

TemperatureSensor

Digital outputs (parallel port)

Serial portAnalog input/output

USB

802.11

LCDSpecialized Processors

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• 8-bit : Intel 8051, Intel 80188, Motorola 6805, Motorola 68hc11, Zilog

• 16-bit: Intel 80186, Motorola 683xx family

• 32-bit: Intel 80386 EX, PowerPC family

• More recent:– ATMEL line of products

Evolution of Embedded Systems (3) Popular microcontrollers

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Evolution of Embedded Systems (4)

Intel PXA250

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Evolution of Embedded Systems (5) Intel PXA800F Cellular processor

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I/O of Embedded Systems

• Application dependent: switches, sensors, hexadecimal keyboard, LCD, basic keypads, communication cards, LEDs

• Rarely:– Monitor, hard-drive, secondary storage, mouse,

keyboard, printer, …