Lecture 13

Introduction to Embedded Systems

Graduate Computer ArchitectureFall 2005

Shih-Hao HungDept. of Computer Science and

Information EngineeringNational Taiwan University

Computing Systems

• Desktop– PC, Workstations, Laptops

• Servers– Tier-0: network appliance– Tier-1: webserver– Tier-2: application/database server– File servers, Storage-area-network

• Embedded Systems– PDA– Cellphone– Routers– Microcontrollers

Embedded?

• Computing system embedded within electronic devices.

• Combination of computer hardware and software designed to performance a specific function.

• Any computing system that is not a desktop computer nor a server.

Area of Applications

• General purpose– PDA

• Control systems– Electronics, Automotive

• Signal processing– Media player, Camera

• Communication– Cellphone, switch

Market

• Average household uses ~225 embedded processors; about 35 for automobile

• Estimated 5 billion embedded processors in use– 94% share of world market– 6%: Pentium, PowerPC, etc.

[Source: World Semiconductor Trade Statistics Bluebook]

Key IssuesUser’s Point of View

• Single function/application– Dedicated to specific type of tasks

• Tight constraints– Size– Power– Cost– Time-to-market

• Real-time– Respond to environment in real time

• Safety/Reliability– Failure can result in critical damages

Key IssuesDeveloper’s Point of View

• Concurrent development of HW and SW, i.e. HW/SW codesign

• Wide selection of uP’s.• Wide selection of OS, mostly real time (RTOS)• Few system resources• Specialized development tools• Debugging skills important• Robust HW/SW

Example

Elements

Trends

• High level of integration– System-on-chip (SoC)– Multiprocessor System-on-Chip (MPSoC)

• HW/SW co-design– Concurrent development– Optimization

• Design flow– Design tools– Experiences

Microcontroller

• Usually a simple uP plus peripheral support devices integrated in a single package

SoC

• A uP plus peripheral support devices integrated in a single chip

• E.g. Intel StrongARM

• SoC vs uController?

SoC Design

• Intellectual Property (IP)– Circuits or cores pre-deisgned/pre-verified for

certain functions– Implications:

• Lower design cost• Fast time-to-market

Requirements

• Functional– Functions– I/O

• Non-functional– Performance– Cost– Power consumption– Size/weight

Architecture

• How to implement the specifications– Components– System structure– Hardware/software partitioning

• HW/SW work together to solve a problem• Partitioning decided by

– Performance– Flexibility– Cost

Architecture Design

Designing An Embedded System

• Understand the big picture

• Understand the details

• Design SW with– Real time constraints– Low power– Small code size

• Domain-specific knowledge