01EMBSYST2007 Ed F.Deprettere1 Embedded Systems and Software Ed F. Deprettere, Todor Stefanov, Hristo Nikolov {edd, stefanov, nikolov}@liacs.nl Leiden

01EMBSYST2007 Ed F.Deprettere

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Embedded Systems and Software

Ed F. Deprettere, Todor Stefanov, Hristo Nikolov

{edd, stefanov, nikolov}@liacs.nlLeiden Embedded Research Center

Spring 2007; Friday 1:30 p.m. – 4:00 p.m.http://www.liacs.nl/~cserc/EMBSYST/

EMBSYST2007/


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Introduction to course

• systems and embedded systems• history of Embedded Systems and Software• examples• complexity issue• trends and challenges• design space exploration• programming and translating• conclusions


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Examination

No formal written exam

Final grade (10) consists of average of three sub-grades

1. active course participation (10) 2. power-point presentation (10) 3. hands-on (10)


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The books1. Computers as Component, Principles of Embedded Computer Systems Design. Wayne Wolf . (Morgan Kaufman Publishers) http://www.ee.edu/~wolf/embedded-book/about.html

2. Embedded System Design. Peter Marwedel. (Kluwer) http://ls12-www.cs.uni-dortmund.de/~marwedel/kluwer-es-book

3. Embedded System Design, A Unified Hardware/Software Introduction. Frank Vahid/Tony Givargis (Wiley) http://www.ics.uci.edu/~sumitg/CadPages.html

4. Fundamentals of Embedded Software. Daniel W. Lewis (Prentice Hall) http://www.prenhall.com/divisions/esm/app/lewis/materials.html5. Embedded Multiprocessors: Scheduling and Synchronization. Sundararjan Sriram and Shuvra S. Bhattacharyya (Marcel Dekker)


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Systems

A system is a composition of functionalities thatjointly realize an input-output behavior in a dependableand secure manner.

Dependable system: can deliver services that arejustifiable trusted (have accepted dependences)

Secure: composite of attributes of • confidentiality (degree of confidence)• integrity (absence of improper system alteration)• availability (readiness for correct service)

Secure: behaves as intended.


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Dependability - Security

Dependability

Readiness Continuity Absence of Absence of Ability tofor Correct of Correct Catastrophic Improper UndergoService Service Consequences System Modification Alteration and Repair

Security

Availability Reliability Safety Integrity Maintainability Confidentiality


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Fault, Error, Failure

Fault : defective value in the state of component or system

Error : indication of occurrence of unspecified internal state

Failure: deviation of behavior from what is specified

fault failure error


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Embedded Systems

An embedded system is a • special-purpose information processing system • that is closely integrated into its environment.

Is Embedded Systems and Software interesting?

Here are the questions, opinions and answers:

Almost all embedded systems are reactive and/or real-time systems (hardware and software).

• Reactive: system maintains a permanent interaction with its environment• Real-time: reactive systems that are subject to externally defined timing constraints.


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Questions

What is specific to research in embedded systems and software?

or is it just the collection of many subjects …

Where are the fundamental questions?

or is it pure systems engineering with lack of methodology …


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Opinion it is NOT interesting

because it is not a well defined research area: it is a mixture of everything, it neglects abstraction, it is without basic scientific questions, it is case-by-case ‘engineering’ only, physicality of embedded software is messy, it is just software engineering for small

computers.


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Opinion it is interesting because of

complex hardware-software interfaces, heterogeneity in specifications and

implementations, complex resource dependencies and interferences, system view (algorithm, architecture, environment,

software), cross-layer design, interaction with physical environment, formal verification and validation.


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Answers

What is specific to research in embedded systems and software?

The impact of the environment The performance analysis in terms of delays and buffer sizes

Where are the fundamental questions? Compositionality (modularity) composability (layering)

scalability, dependability and security Design space exploration


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Answers (2)

Move successful concepts (like abstraction and modularity) to embedded systems

Do meaningful experiments that are carefully planned (learn from physics …)


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System-Level Performance Analysis

InputStream

InputStream

I/O

P

Memory Requirements?

Processor Speeds?

Timing Properties?

Bus Utilization? Bottleneck

?


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Difficulties

InputStream

Complex Input:- Timing (jitter, bursts, ...)- Different Event Types

Task Communication

Task Scheduling

ab acc b


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DifficultiesProcessor

Task

BufferInput

Stream

Task Communication

Task Scheduling

ab acc b

Complex Input:- Timing (jitter, bursts, ...)- Different Event Types

Variable Resource Availability

Variable Execution Demand- Input (different event types)- Internal State (Program, Cache, ..)


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Embedded Systems

powerliveness

reactivity

weight timelinesscost reliability

adaptabilityenergy

resource-awareness

predictabilitymulti-objective


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Abstraction

... E E E E E E ...

ProcessorTask

InputStream

Functional UnitModel

ResourceModel

Event StreamModel

Composition &Analysis

System Module

Concrete Instance

Abstract Representation


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HistoryIn past, embedded systems were called (embedded)controllers (micro-controllers). They appear typicallyin control dominated applications.

Examples: traffic lights, elevators, washers, dryers, vendor machines ATM machines

These are relatively simple finite state machines implemented using either micro-controllers or sequential circuits (programmablelogic arrays – PLA)

PLA

registers

inputs outputs

current state next state


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Product: Hunter Programmable Digital Thermostat.

Microprocessor: 4-bit

Some small examples


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Product:Vendo V-MAX 720 vending machine.

Microprocessor: 8-bit Motorola 68HC11.


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Product: Miele dishwashers.

Microprocessor: 8-bit Motorola 68HC05.


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Product: NASA's Mars Sojourner Rover.

Microprocessor: 8-bit Intel 80C85.


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Product: Sony Aibo ERS-110 Robotic Dog.

Microprocessor: 64-bit MIPS RISC.


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History (cont’d)

With growing complexity of applications some processing of signals was added to pure finite state machine behavior : FSMs became EFSMs(extended finite state machines).

With still more growing complexity concurrency andparallelism become important. E.g., communicating (E)FSMs. Here is what is happening.


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Complexity Issue

Systems can be (extremely) complex:

• wafer steppers• imaging (medical, biology, astronomy)• wafer stepper• imaging (medical, radar, telescope)• digital copiers/printers

Embedding systems – hence embedded systems – maybe (extremely) complex.

On-chip transistor density

Expected

Actual

time

app

licatio

n comp

lexity/p

erfo

rman

ce

Shared memory architecture


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Complexity Issue (cont’d)

• wafer stepper• imaging (medical, radar, telescope)• digital copiers/printers

Embedding systems – hence embedded systems – maybe (extremely) complex.

On-chip transistor density (Moore’s Law)

Expected

Actual

time

app

licatio

n comp

lexity/p

erfo

rman

ce

Shared memory architecture

Application complexity (Shannon Law)


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μP will do for small systems

For many consumer products, a single μProcessor will do.

For other systems – such as a car – a network ofμProcessors is needed.

For even larger systems – heterogeneous multi-processorEmbedded Systems are needed


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Heterogeneous Architectures

Heterogeneous architectures consist of programmable and dedicated components

TM

Mem

CP1 CP2

MIPS

Programmable core + SW

Dedicated coprocessor


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Trend in Multi-processor

• current state of art: co-processor P FPGA

• next: multi-processor

• then: heterogeneous multi-processor

P

P

P

P

Communication StructureCommunication Structure

MemMem

PE

PE ...

...

PE

PE PE

PE PE

PE

MemMemMemMem MemMem

• later: networks on chips

Identical tiles(scalable)


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Challenges

How to design such complex architectures?

How to program such complex architectures?

Available design tools fall short to do the job

Available programming paradigms are poor


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Embedded Systems and Software

The relative weight of software in the value of ES is constantly increasing.

The extensive and increasing use of ESS and their integrationin every day products marks a significant evolution in informationprocessing, science, and technology.

Strategic shift from simply achieving feasibility to achieving optimality,meaning: • targetting a given market segment at low cost and fast delivery time• seamless integration with physical environment while respecting real- world constraints (deadlines, reliability, availability, robustness, power consumption, and cost).

Multidisciplinary (general computer science and engineering,real-time computing, system architecture, control and signal processing, security and privacy, networking, mathematics, electronics).


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Example: Trimedia

VLIWcpu

I$

video-in

video-out

audio-in

SDRAM

audio-out

PCI bridge

Serial I/O

timers I2C I/O

D$

Programmable core

peripheralsOff-chip memory

High-way bus


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Application domainsApplications as shown are from a particularapplication domain called streaming data applications

Audio, image processing, video, graphics, etc

The peripherals take care of the (input and output) data streams

The programmable core does the processing of the data in thestreams. The Trimedia shown is a first generation processor(later generations have more parallel processing capabilities;see later).

The programmable core is a so-called very large instruction wordarchitecture: parts of a long instruction are interpreted and executed byissue slots that operate in parallel. The VLIW architecture relieson a compiler as do all general purpose processors.


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TriMedia CPU64 Architecture

datacache16KB

datacache16KB

mmummu

mmummu

64-bitmemory

bus multi-port 128 words x 64 bits register filemulti-port 128 words x 64 bits register file

FUFU FUFU FUFU FUFUFUFU

instructioncache32 KB

instructioncache32 KB

mmummu

bypass networkbypass network

PCPCexceptions exceptions

32-bitperipheral

bus

VLIW instruction decode and launchIssue slots

Very large instruction words


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(Embedded) System (cont’d)

In this course we envision an (embedded) system asthe triple < application, architecture, mapping>and an (embedded) system model as the triple < application model, architecture model, mapping transformations>

This is compliant with the separation of concernsprinciple (See later).


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Design Space Exploration

Application Architecture

Mapping

Analysis

(Semi-) AutomatedDesign SpaceExploration


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Maximize (y1, y2, …, yk) = (x1, x2, …,

xn)y2

y1

Pareto optimal = not dominated

dominated

y2

y1

worse

better

incomparable

incomparable


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Single vs. Multiple Optimization

cost

performance

single objective

total order

single optimum

multipleobjectives

partial order

multiple optima


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Design Space Exploration

194 195 196 197 198 199 200 201 202 8.6

8.8

9

9.2

9.4

9.6

9.8

10x 10

area

cy

cle

s

Vary # functional units (issue slots)

Vary allocation of functions

Cost model of functional units

Pareto points


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Some other trends

1. Move from central processing to distributed processing2. Plug and play standardization (HW and SW)3. Smart devices/cards4. Ubiquitous computing

Distributed on-chip and off-chip

What is common in PC world will be so in others (e.g., TV;- but: reliability is a major issue)

There are many (see RFIDs Scientific American, Jan. 2004)

See http://ubiq.com/hypertext/weiser/UbiHome.html

Sensor networks


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sensor networks (civil engineering, buildings, environmental monitoring, traffic, emergency situations)

smart products, wearable/ubiquitous computing


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Programming/translating

Application

Programmable Interconnect (NoC)Programmable Interconnect (NoC)

IPcore

IPcore

RP

UR

PU

Mem

oryM

emory

CP

UC

PU

Micro

Processor

Micro

Processor

MemoryMemory

...

Programming

P1 P2

S1Source

P3 P4

Sink

Parallel (Compaan PN) Application Specification

EASY to map

DIFFICULT to specify

for j = 1:1:N, [x(j)] = Source1( ); endfor i = 1:1:K, [y(i)] = Source2( ); endfor j = 1:1:N, for i = 1:1:K,

[y(i), x(j)] = F( y(i), x(j) ); endendfor i = 1:1:K, [Out(i)] = Sink( y( I ) ); end

Sequential Application Specification

EASY to specify

DIFFICULT to map

Compaan

Laura


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And down (an example)CPN

Network of Virtual Processors

CPNtoPlatform

Mapping

Library ofIP cores

Network of Synthesizable Processors

Verilog SystemCVHDL

Platform dependent

Platform Independent


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ConclusionChallenges in Embedded Systems and Software

• New Applications

huge demands for computation, communication, and memory multiple applications in resource-constrained system• Heterogeneous multi-processor HW/SW platforms• Programming of multi-processor platforms

automated code transformations guaranteed real-time constraints dynamism in applications, in SW, in HW (migration/configuration)

• New paradigms raising level of abstraction re-use, interfaces, integration platform based (software and hardware platforms) dependability and security


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Conclusion (cont’d)

There is a need of modeling applications andarchitectures at abstract levels.

And a need of transformations to map applications toparallel implementations

In other words, a need of a theory of embedded systems.

Documents

01EMBSYST2007 Ed F.Deprettere1 Embedded Systems and Software Ed F. Deprettere, Todor Stefanov, Hristo Nikolov {edd, stefanov, nikolov}@liacs.nl Leiden