Introduction to Embedded Systems

Introduction
To
ES
Mohamed Abd Elhay

Copyright © 2012 Embedded Systems
Committee

Committee

 Embedded Systems
 Embedded Systems Applications
 Embedded Systems Types
 Memories

 Embedded system developing
 Embedded Systems Market in Egypt
Committee

Copyright © 2014Embedded Systems
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•Embedded system is a special purpose system designed to
perform one or a few dedicated
functions.
• Embedded systems are computing systems with tightly
coupled hardware and software integration.

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The Word “Embedded” reflects the fact that these systems are
usually an integral part of
a larger system, known as the embedding system.

“A computer built into a system and not seen by the user as
being a computer”
It is usually Embedded as a part of a complete device
including hardware and mechanical parts.

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Can Personal Computer be considered as an Embedded
System as it integrates hardware and software to
perform functions? Why?

NO
PC cannot be considered as an embedded system
because
1. It uses a General-Purpose Processor
2. The system is built independently from the software
runs on it.

Else ATM machine
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Communication:
Mobile Handsets
Switches and Routers
Image processing and Consumers:
Cameras
Mp3 and Mp4 players
PlayStation
Automotive:
Engine Management System
Claimant Control System
Appliances:
Microwave
Washing Machines
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1) Microprocessors.
2) Microcontrollers.
3) DSPs.

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o CPU = ALU + Registers + Control unit
o Microprocessor function is to fetch the instructions
from the memory then decode and execute them.

o Microprocessor alone is useless

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CPU design divide into three parts:

o The datapath
does all of the actual data processing

o A control unit
uses the programmer’s instructions to tell
the datapath what to do

o An instruction
set is the programmer’s interface to CPU
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Control Unit and Datapath

Control Unit
and

Datapath

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o The hardware part of the processor that
performs the processing operations.

o Contain from Three Parts:
Computations
Fast temporary storage
Large memory storage

ALU
Register file
RAM

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o programs with the data-path :
converts program instructions into control
signals for data-path.
Executes program instructions in the correct
sequence.

V
C
N
Z

Branch
Control

PC

ADRS
Instruction
RAM
OUT

Instruction Decoder
DA AA BA MB FS MD

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WR

• CPU = ALU + Registers + Control unit
Datapath

Control Unit
V
C
N
Z

D

W R
DA

PC
ADRS
Instruction
RAM

Register file

AA

Branch
Control

A

B

B A

constant
1
0
Mux B

MB

OUT

Instruction Decoder
DA AA B A

MB FS MD W R

FS
V
C
N
Z
MW

A

ADRS

B
ALU

MW

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Data RAM
OUT

G

0
1
Mux D

DATA

MD

Harvard arch.:
includes two memory units :
o
o

o

An instruction memory holds the program
A separate data memory is used for
computations
The advantage is that we can read an instruction
and load or store data in the same clock cycle

Von Neumann arch.:
includes one memory unit :
o

a single main memory that holds both program
instructions and data
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RISC

CISC

Reduced Instruction Set Computer

Complex Instruction Set Computer

optimize execution of instructions by
single instruction limiting capabilities

integrate several functionalities in one
instruction

The Compiler is simple as has wide verity of
The compiler or programmer
synthesizes complicated operations instructions to perform the complicate
operation
by combining several simple
instructions. (ex: divide operation)

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:
RISC

CISC

simple operations that can each
execute in a single cycle

the instructions are often take many cycles to
execute.

have a large general-purpose register
set.

dedicated registers for specific purposes

Any register can handle with ALU

dedicated registers specific for ALU operation

ALU can‟t deal with Memory directly

ALU can deal with memory directly

Due to Memory accesses are costly :

the core can operate at higher clock
frequencies.

and operate at lower clock frequencies

Separate load and store instructions
transfer data between the register bank
and external memory are needed to all
ALU operations

Separate load and store instructions transfer
data between the register bank and external
memory aren’t needed to all ALU
operations

Copyright
Helps to pipeline execution of instructions © 2014 Embedded Systems
Committee

:
• Microcontroller = CPU + Memory + Peripherals
•Designed for standalone operation.

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:
Microcontroller Main Components
Microcontroller has eight main components:
1. Central processing unit (CPU)

2. ROM
3. RAM
4. Input and Output (GPIO or DIO)

5. Timer
6. Interrupt circuitry
7. Buses

8. Watchdog
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• Like microcontrollers BUT Focus on very efficient execution of
arithmetic operations.
• DSP has :
o specialized arithmetic units,
o optimized design in the memory,
o Addressing and bus architectures with multiprocessing capability
that allow the DSP to perform complex calculations extremely fast
in real time.
• Used widely in digital signal processing in communications systems
such as Cell phones and Image and video processing.
• TI (Texas Instruments) has been the dominant player in the DSP market
for several years.
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Multi-core system on chip
Like mobile handset which has one chip contains:

o DSP processor
o Embedded processors like ARM

o Custom hardware for GSM
o Custom peripherals for board interface (keyboard,
touch screen, memory card interface)
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1-Program Memory
MROM
•
•
•
•

Masked ROM
Programmed by the manufacturer.
The term „masked‟ comes from the manufacturing process
In case of a large-scale production, the price is very low.

PROM
•
•
•
•

Programmable rom
Also called One time programmable ROM
enables programmer to download a program into it one time only.
If an error is detected after downloading, the only thing you can do is
to download the correct program to another chip.
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1-Program Memory
UV EPROM
• UV Erasable Programmable ROM
• It enables data to be erased under strong ultraviolet light.
• After a few minutes it is possible to download a new program.

EEPROM
• ELECTRICALLY ERASABLE PROGRAMMABLE ROM
• can be erased by exposing it to an electrical charge

Flash Memory
•
•
•
•

Invented in the 80s in the laboratories of INTEL
Represented as the successor to the UV EPROM.
Can be written and cleared practically an unlimited number of times,
most microcontrollers are manufactured in flash technology.
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2-Data Memory
SRAM:
• Static random access memory
• uses multiple transistors, typically four to six, for each memory cell
• doesn't have a capacitor in each cell.

DRAM:
• Dynamic random access memory
• has memory cells with a paired transistor and capacitor requiring
constant refreshing.

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Trade off between HW and SW
For a certain application
o Which functional blocks should be performed in Hardware??

o Which functional blocks should be performed in software??

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Software characteristics
o Highly configurable
o Shorter development cycle
o Easier in versions updates
o Cheaper

o Constrained with processor speed which may satisfy real time
application and may not
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Hardware characteristics
o Longer development cycle

o Customized for specific application
o Better performance in high speed real time application

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SYSTEM ON BOARD
Board

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SYSTEM ON CHIP
Keyboard
controller

LCD
controller

USB interface

CPU

Memories

Customized
hardware

ASIC Chip

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HW / SW Partitioning
• In complicated systems functional blocks could be:

o Level 1: External discrete hardware component on board.
o Level 2: Hardware integrated with CPU on chip (SoC).
o Level 3: Done by software running on CPU.

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“Those systems in which the correctness of the system
depends not only on the logical result of the computation, but
also on the time at which the results are produced”
Real Time Systems are a very fast systems?
Real-time means completing tasks within specified deadlines,
it is not defined or limited by a specific execution speed.

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System Development Cycle
1. System Specification Analysis
2. System Design
3. Development

 Hardware Development
 Software Development
4. System Integration

5. System Validation

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Software Development Cycle
1-Software Specification
2-Software Design
3-Coding / Testing

4-Software Integration
5-Software Validation

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1- Assembly
a-Lowest level human readable
b-Platform specific.
c-Assembly has one-to-one corresponding machine language
d-Using compiler to convert High Level language to Assembly

2-C Language

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References

• ESC Training Team

Committee

info@escommittee.net

Committee

Introduction to Embedded Systems

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