Embedded System Architecture

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Embedded SystemArchitecture

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Embedded System ArchitectureEvery embedded system (ES) is composed of

interacting elements (hardware or software).

An architecture is a set of representations of thoseelements and their relationships.

Architecture helps understanding the whys of the

elements with given functionalities.Defining and understanding the architecture of an ES

is an essential component of good system design.

An architectural systems engineering in an ES helps understanding the design

is essential to resolve challenges when designing anew system

helps design re-use, reduces design time and cost.


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Embedded System Architecture

An embedded architecture captures various views,which are representations of the system.

It is thus a useful tool in understanding allof themajor elements: Why each component is there?

Why the elements behave the way they do?

Without an architecture design it is difficult todetermine how the system would behave under avariety of circumstances in the real world.

The architecture conveys in some way the criticalcomponents in a design and their relationships toeach other.

Even if the architectural structures are rough andinformal, it is still better than nothing.


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Embedded Systems Model

The embedded system model

indicates that at the highestlevel, they have

at least one layer (hardware)

or

all layers (hardware, system

software and applicationsoftware) into which all

components fall.

This model is essentially a

layered (modular) model of an

ES architecture.

It gives visual representation

of the main elements and

their associated functions.

The hardware layer contains all

the physical components.

The system software layercontains all the software

located on the ES.

The application software layer

contains all the SW being

processed by the ES.


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Networks Architecture in ES

The ES is a networking of

internal components and thenetworks architecture.

Good to associate the

networking components with a

universal networking model, the

seven layer OSI reference model. Data originating at the

application layer flow downward

through all seven layers.

Information (header) is

appended to the data at eachlayer (except for the application

and physical layers).

Data is wrapped with information

for other devices to unwrap and

process.

Mapping

OSI layers ES layers

Physical Hardware

Data-linkNetwork System SWTransport

Session

Presentation Application SWApplication


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OSI Model and Real World Protocol

The functionalities and methodologies implemented at

each layer based on the OSI model are commonlyreferred to as netwo rk ing protocols .

It isnt always the case that there are all seven layers orthere is just one protocol per layer.

The functionality of one layer of the OSI model can beimplemented in one protocol, or also it can beimplemented across multiple protocols and layers.

A group of protocols may have their own name and begrouped together in their own proprietary layers.

Examples are:

TCP/IP WAP Bluetooth


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The TCP/IP, OSI and ES Models

The TCP/IP stack is made up of four layers.

OSI layers TCP/IP layers

Top three (App, Presentation, Session) TCP/IP App layerTransport layers Transport layer.Network layer

Internet layerTwo OSI layers (Data Link and Physical) Network access layer


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The OSI, WAP and ES Models

The Wireless Application Protocol (WAP) stack provides five layers ofupper layer protocols.

OSI layers WAP layersApplication layer WAP Application layerPresentation layer Security layerSession layer Session + Transaction layerTransport layer Transport layer


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The Bluetooth, OSI and ES Models

OSI layers Bluetooth

layers

Physical andLower Data Link

layers

Transport ProtocolGroup

Upper Data link,

Network +Transport layer

Middleware

Protocol Group

Session,

Presentation +

Application layer

Application

Protocol Group

The Bluetooth stack is a three-layer model made up of

Bluetooth-specific as well as adopted protocols from

other network stacks, such as WAP and/or TCP/IP .


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(1) Physical Layer Protocols in the ES Models

The Physical Layer represents all of the networking HW physically locatedin an embedded device. It defines, manages, and processes, viahardware, the actual voltage representations of 1s and 0s.

Physical layer protocols defining the networking hardware of the deviceare located in the hardware layer of the ES model.

Physical layer protocols are classified as either LAN or WAN protocols.

They can be further subdivided according to the transmission medium

connecting the device to the network (wired or wireless).


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(2) Data-Link Layer Protocols in the ES

Includes any software needed to control the hardware.Bridging also occurs at this layer.

Data-link layer protocols can be used for (i) LAN, (ii) WAN, or (iiii) both.

Can be wired or wireless.

Generally, reliant on a specific physical layer.

May also be ported to very different mediums.Supports hardware-independent upper-data-link functionality.

Data-link layer

protocols areimplemented in

the system

software layer.

Closest to the

hardware layer.


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(3) Network Layer Protocols in the ES

Networks can be divided into smaller sub-networks, called segments.

Devices within a segment communicate via their physical addresses.

Devices in different segments communicate through an additional address,

called the network address.

Conversion between physical addresses and network addresses can occur in

the data-link layer protocols (i.e. ARP, RARP etc.)

Network layer protocols can also convert between physical and networkaddresses as well as assi n network addresses.

Implemented in the

system software

layer.

Is typically hardware

independent.

Depends only on the

data-link layer

implementation.


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(4) Transport Layer Protocols in the ES

Ensures reliable point-to-point data transmission, by ensuring that:

1. packets are received and transmitted in the correct order

2. transmitted at a reasonable rate

3. packets are not corrupted

4. Provides acknowledgement on receiving

5. Requests retransmission in case of detection of error.

Transport layer

protocols sit on topof and are specific

to the network layer

protocols.

Are typically

responsible for

communicationbetween two

specific devices

(point-to-point)

communication.


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(5) Session Layer Protocols in the ES

The session layer protocols1. Separate and manage each sessions data

2. Regulate the data flow of each session

3. Handle any error

4. Ensure the security of the session

5. Ensure that the two applications involved in the session are the righta lications.

The connection

between two

networkingapplications on two

different devices is

called a session.

The management of a

session is handled bythe session layer.

Generally, sessions

are assigned a port

(number).


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(6) Presentation Layer Protocols in the ES

1. Presentation layer protocols are usually implemented in

networking applications in the application software layer in ES.

2. Data compression/decompression, data encryption/decryption,

data protocol/character conversions.

Protocols in the

presentation layerare responsible for

translating data into

formats that higher

applications can

process.


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(7) Application Layer Protocols in the ES

1. A device initiates a network connection to another device at theapplication layer.

2. Application layer protocols are either used directly as network

applications by end-users or the protocols are implemented in

end-user network applications.

3. These applications virtually connect to applications on otherdevices

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Embedded System Architecture