By: Zakriua Gomma
Email: zakriua.gomma37@gmail.com
Introduction to Embedded System

What is an Embedded System?
 Embedded : means hidden inside so one can’t see it .
 System : means multiple components interfaced together for
do special purpose .
 Embedded System : is a special-purpose computer system
designed to perform certain dedicated functions.
 Functionalities : are done by dedicated HW and SW with
limited resources.
 On average, a person interacts with 100s of embedded
systems on daily basis.

What is an Embedded System?

Embedded Systems - Examples
• Any PC Mouse,
Keyboard, or USB
Device.
• Microcontroller:
8-bit.

Embedded Systems - Examples
• Any Disk Drive has
an embedded
Microcontroller
• Any Printer has an
embedded
Microcontroller

Embedded Systems - Examples
• Product: Creative Labs
Zen Vision:MVideo &
MP3 Player.
• Microcontroller: TI
TMS320 DSP.
• Canon EOS 30D Digital
Camera.
• DIGIC II Image
Processor.

Embedded Systems - Examples
• NASA's Twin Mars
Rovers.
• Microprocessor:
Radiation Hardened
20MHz PowerPC From
IBM
• Commercial Real-time
OS.
• Software and OS was
developed during
multi-year flight to
Mars and downloaded
using a radio link.

Embedded Systems - Examples
• Agilent Oscilloscope.
• Microprocessor: X86.
• OS: Windows XP.
• Product: Atronic Slot
Machine.
• Microprocessor: X86.
• OS: Windows CE.

Embedded Systems - Examples
• Sphero BB-8
• ARM Cortex-M4 core 32bit From ST

Embedded Systems - Examples
Sphero BB-8 From inside

Embedded Systems - Examples
• Sony Aiborobotic
dog.
• Microprocessor:
64-bits MIPS
RISC.

Embedded Systems - Examples
• BMW 745i
• Windows CE OS.
• 53 8-bit µP.
• 11 32-bit µP.
• 7 16-bit µP.
• Multiple Networks.

Embedded Systems - Examples

Embedded Systems Applications

Computer Hardware
Microprocessor
A Large Memory:
(Primary & Secondary)
(Ram ,Rom ,Cache)
Input Units:
(Mouse, Keyboard ,Scanner ,etc.)
Output Units:
(Monitor ,Printer ,etc.)
I/O Units:
(FAX ,Ethernet,etc.)
Storage Units:
(Hard disk.)

Computer Hardware

Computer Hardware

Embedded System Hardware
Microcontroller which contain :
Processor, Timers, Interrupt controller, I/O Devices, Memories, Ports, etc.
All on Single Chip Or System On Chip (SOC).

Embedded System Hardware

MicrocontrollerMicroprocessor
Slower clock speedHigher Clock speed
CPU,RAM, ROM, I/O and timer
are all on a single chip
CPU is stand-alone, RAM, ROM,
I/O, timer are separate
Fix amount of on-chip ROM,
RAM, I/O ports
Designer can decide on the amount
of ROM, RAM and I/O ports
CheapExpansive
Single-purposeGeneral-purpose
Low Access time for memoryHigh Access time for memory
Low powerVery High power

CPU Architectures
1) Princeton Architecture (Von Neumann Architecture) :
Between 1945 & 1951 John von Neumann set down the structure, layout,
interaction, cooperation, realization , implementation, functionality and
activity for the whole computer as a system. The Von Neumann
Architecture is characterized by: -
 A memory, arithmetical-logical unit (ALU), control unit, input and output
device…. etc.
 All parts of a computer are connected together by Bus.
 Memory and Devices are controlled by CPU .
 Data can pass through bus in half duplex mode to and from CPU.
 Memory is split to small cells with the same size. Their ordinal numbers are
called address numbers.
 Each time CPU fetches a program instruction it may have to perform one or
more read/write operation “instruction” from/to data memory space. It must
wait until these subsequent “instruction“ are complete before it can fetch and
decode the next program instruction.

CPU Architectures
Princeton Architecture (Von Neumann Architecture) :

CPU Architectures
Princeton Architecture (Von Neumann Architecture) :

CPU Architectures
Princeton Architecture (Von Neumann Architecture) :

CPU Architectures
2) Harvard Architecture:
The Harvard Mark II was finished at Harvard University in 1947 . It
wasn’t so modern as the computer from von Neumann team. But it
introduced a slightly different architecture. Memory for data was
separated from the memory for instruction. This concept is known as the
Harvard Architecture :
 There is no need to make the two memories share characteristics. In particular,
the word width, timing, implementation technology, and memory
address structure can differ.
 The CPU can read an instruction and perform a data memory access at the
same time..
 This speeds up execution time but increases the cost of more hardware
complexity.
 If, for instance, every instruction run in the CPU requires an access to memory,
the computer gains nothing for increased CPU speed—a problem referred to as
being "memory bound".

CPU Architectures
Harvard Architecture:

Von NeumannHarvard
Used in conventional processo
rs found in PCs and Servers,
and embedded systems with
only control functions.
Used in DSPs and other processors
found in latest embedded systems
and Mobile communication systems,
audio, speech, image processing
systems
One bus is simpler for the
control unit design
Control unit for two buses is more
complicated and more expensive
The code is executed serially
and takes more clock cycles
The code is executed in parallel
Avg computation speed is lowAvg computation speed is high

CPU Architectures
For Processors :
Von Neumann is used in Processors because, unlike MCUs, processors don’t have
internal memory or peripherals and the connection to memory is through external
bus and Von Neumann is suitable because:
 Cost: less buses means less cost.
 Space: we don’t need to waste large space of motherboard.
 Processors mainly deal with only one memory, RAM which holds the
data and instructions, so only one bus will be suitable and the slow
access will be substituted by the high speed of the processor and
using the cash memory.
For Microcontroller :
Harvard architecture is used in MCU because:
 Microcontroller contains everything on the chip. RAM, flash, and
peripherals and due to the small size using multiple buses is not an
issue.
 Microcontroller speed is not high so multiple buses will help with
the limited speed of MCU.
Which is the best ?

CPU Structure
The basic elements of the CPU are:
• ALU
 Arithmetic & Logic Unit
 Responsible for performing logic and arithmetic
calculations.
• Floating-Point Unit (FPU)
 performs arithmetic operations on floating
point numbers.
• Registers
 Registers are used to store data beside the ALU
 Registers are used to transfer data to/from
memory
 Registers carry the inputs of ALU, as well as,
receiving the output of the ALU.
• Internal CPU Bus
 It is a special bus.
 It is responsible for transferring data between
registers, ALU, and system memory
• Control Unit
 It is responsible for organizing the actions of the
CPU
 It can be thought of as the heart of the CPU

CPU Structure
Arithmetic logic unit :
• ALU is a digital circuit that performs :
 Arithmetic operations :
o Add, Sub,….etc.
 Logical operations :
o And, Or, Not,…etc.
• Operates and stores results in general
registers
• Stores operation status in flag/status
registers
 Carry occurrence, overflow occurrence

CPU Structure
FPU ( Floating-Point Unit):
• The FPU performs arithmetic operations on floating point numbers.
• An FPU is complicated to design, although the IEEE 754 standard
helps to answer some of the specific questions about implementation
• 8086 : First computer to implement IEEE FP
• Three types of the Floating-Point Data :
 The half-precision floating-point format (16-bit data)
 The single-precision floating-point format (32-bit data)
 The double-precision floating-point format (64-bit data)

CPU Structure
IEEE Floating Point Standard 754 (FPS)
1. Half precision :
 16-bits
– 10-bit mantissa
– 5-bit exponent
– 1-bit sign
2. Single precision :
 32-bits
– 23-bit mantissa
– 8-bit exponent
– 1-bit sign
3. Double precision :
 64-bits
– 52-bit mantissa
– 11-bit exponent
– 1-bit sign
31 30 23 22 0
S Exponent Mantissa (bits 0-22)
63 62 52 51 0
S Exponent Mantissa (bits 0-51)
15 14 10 9 0
S Exponent Mantissa (bits 0-22)

Pipeline :
• Continuous and parallel streaming of instruction to the CPU.
• A method of achieving higher execution speed at same clock
speed.

Pipeline :

Pipeline :

Pipeline :

Pipeline :

Pipeline With a Branch Penalty :

Super Pipeline :

Superscalar vs.
Super pipeline
• Simple pipeline system
performs only one
pipeline stage per clock
cycle
• Super pipelined system is
capable of performing
two pipeline stages per
clock cycle
• Superscalar performs only
one pipeline stage per
clock cycle in each
parallel pipeline

MIPS:
• The number of machine code instructions a computer can process while
executing a "standard" program is measured in MIPS (Million Instructions
Per Second). Specifically
• MIPS is a method of measuring the raw speed of a computer's processor
and is defined as the number of machine instructions (in millions) that a
processor can execute in one second.
• 𝑀𝐼𝑃𝑆 =
𝑃𝑟𝑜𝑐𝑒𝑠𝑠𝑜𝑟 𝐶𝑙𝑜𝑐𝑘 𝐹𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦 (𝑀𝐶𝐿𝐾)
𝐴𝑣𝑒𝑟𝑎𝑔𝑒 𝐶𝑦𝑐𝑙𝑒𝑠 𝑝𝑒𝑟 𝐼𝑛𝑠𝑡𝑟𝑢𝑐𝑡𝑖𝑜𝑛 (𝐶𝑃𝐼) ∗ 1,000,000
=
𝑐𝑦𝑐𝑙𝑒𝑠 / 𝑠𝑒𝑐𝑜𝑛𝑑
𝑐𝑦𝑐𝑙𝑒𝑠 / 𝑖𝑛𝑠𝑡𝑟𝑢𝑐𝑡𝑖𝑜𝑛
=
𝑚𝑖𝑙𝑙𝑖𝑜𝑛 𝑖𝑛𝑠𝑡𝑟𝑢𝑐𝑡𝑖𝑜𝑛𝑠
𝑠𝑒𝑐𝑜𝑛𝑑

MIPS:
ClockMIPSProcessor
5 MHz.33Intel 8086
12.5 MHz12.5Analog Devices ADSP
-2100
20 MHz5Microchip PIC16F
600 MHz2.054Intel Pentium III
1.2 GHz3,561AMD Athlon
500 MHz28,293,540NEC Earth Simulator
( 5120 cores)
100 MHz125ARM Cortex-M3
1 GHz2,100Qualcomm Scorpion
(Cortex A8)
1.2 GHz4,744Raspberry Pi 2
3 GHz238,310Intel Core i7 5960X
3.2 GHz9,726Pentium 4 Extreme
Edition

MIPS:

Instruction set architecture (ISA)
 The computer ISA defines all of the programmer-visible
components and operations of the computer
 memory organization
 address space -- how may locations can be addressed?
 addressability -- how many bits per location?
 register set
 how many? what size? how are they used?
 instruction set
 opcodes
 data types
 addressing modes
 ISA provides all information needed for someone that
wants to write a program in machine language (or translate
from a high-level language to machine language).

CISC & RISC
RISCCISC
Reduced Instruction set ComputerComplex Instruction Set Computer
Less no of instructionsMore no of instructions
Programming is difficultProgramming is easy
PIC,AVR, ARM8085,8086,Pentium
Only LOAD/STORE refer memoryAny instructions may refer memory
Highly pipelinedNot pipelined or less pipelined
large code sizesSmall code sizes
Instructions execute in one clock
cycle.
Instructions generally take more than
1 clock to execute.
Simple in DesignComplex in Design

Memory Unit:
• Memory is a part of the Any Computer System used for data storage.
• Types of Memory :
 Volatile Memory .
 Non Volatile Memory .

Memory Unit:
Volatile memory :
RAM memory (Random Access Memory) :
• Refers to the ability to access any memory cell directly. RAM is
much faster than ROM . It used to write and read data values
while program running .
• Volatile : if you remove the power supply its contents are lost.
• Any variable used in a program is allocated into RAM.
• local variables, pointers, functions, recursive functions results
in using large amounts of RAM
• Types Of RAM :
 Dynamic RAM (DRAM)
 Static RAM (SRAM)

Memory Unit:
Static RAM
Dynamic RAM

Dynamic RAM (DRAM)Static RAM (SRAM)
Made From capacitorsMade From flip-flops.
Low cost (per bit)High cost (per bit)
Low using powerHigh using power
SlowFast
Used in main memoryUsed in cache Memory
Low in SizeLarge In size
Automatically discharges after
sometime, need refreshing
Will retain state forever

Memory Unit:

Memory Unit:

Memory Unit:
Small amount of memory that is faster than RAM
Slower than registers
Built using SRAM
Range from few KB to few MB
Use by CPU to store frequently used instructions & data
Spatial & temporal locality
Use multiple levels of cache
L1 Cache – Very fast, usually within CPU itself
L2 Cache – Slower than L1, but faster than RAM
Today there’s even L3 Cache
Cache Memory

Memory Unit:
L1 & L2 Cache

Memory Unit:
Cache Read Operations

Memory Unit:
Caching in Multi-Core Systems

Memory Unit:
Caching in Multi-Core Systems (Cont.)

Memory Unit:
Core i7 Die & Major Components

Memory Unit:
Non-Volatile memory :
• ROM(Read Only Memory):
 Permanent memory(Non-Volatile memory).
 Used as Program Memory in Micro-Controller.
 ROM generally slower than RAM.
 The size of program that can be written depends on
 Written upon programming the microcontroller.
 Can't be written/modified at run time.
• ROM Types:
 Masked ROM .
 OTP ROM .
 UV EPROM .
 EEPROM .
 Flash EEPROM .

Memory Unit:
1-Masked ROM (MPROM) :
-Programmed by the manufacturer.
-The term ‘masked’comes from the manufacturing
process.
-In case of a large-scale production, the price is
very low.

Memory Unit:
2-OTP (One Time Programmable):
- Also called programmable ROM(PROM).
- Enables programmer to download a program into it one time only.
- Used when the firmware is stable and the product is shipping in bulk to
customers.
- If an error is detected after downloading, the only thing you can do is to
download the correct program to another chip.

Memory Unit:
3- 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 pro
gram
- the package of this microcontroller has recognizable“”wi
ndow””on the upper side. It enables surface of the silicon
chip to be lit by an UV lamp, which has as a result that
complete program cleared and a new program download
enabled

Memory Unit:
4-EEPROM(Electrically Erasable Programmable ROM)
- Can be erased by exposing it to an electrical charge.
- The contents of this memory may be changed during run
time (similar to RAM),but remains permanently saved
even if the power supply is off (similar to ROM)
- EEPROM is often used to read and store values , created
during operation, which must be permanently saved.
- Acts as peripheral of microcontroller.
- Take more time in read/write access than RAM
- The max number to Write/Erase Cycles is usually100,000
but in Read is infinity

Memory Unit:
5-Flash EEPROM
- Invented in the 80s in the laboratories of Intel.
- Represented as the successor to the EEPROM.
- Flash is normally organized as sectors (256B - 16KB).
- Large blocks of memory erased at once, rather than one
word at a time like EEPROM , So FLASH is much faster th
an EEPROM . Take more time in read/write access than
RAM
- The max number to Write/Erase Cycles is usually10,000
but in Read is infinity

Memory Unit:
speedCost per
bit
Max Erase
cycles
Erase sizeWriteable
?
Volatile
?
Type
FastExpensiveunlimitedByteYesYesSRAM
ModerateModerateunlimitedByteYesYesDRAM
FastInexpensi
ve
----NONoMasked ROM
FastModerate----OnceNoPROM
FastModerateLimited(consult
(datasheet
Entire chipYesNoEPROM
Fast to read
slow to write
ExpensiveLimited(consult
(datasheet
byteYesNoEEPROM
Fast to read
slow to write
ModerateLimited(consult
datasheet)
sectorYesNoFLASH

Microcontrollers Selection Criteria:

Microcontrollers Selection Criteria:
HC11(Motorola)PIC(Microchip)8051(Intel)AVR(Atmel)
Von NeumannHarvardVon-NeumannHarvardArchitecture
CISCRISCCISCRISCInstruction Type
8MHz20MHz24MHz20MHzMax speed
84121Cycle/Instruction
1MIPS5MIPS2MIPS20MIPSInstruction/second
20032215132N of Instructions
32KB64KB32KB256KBMax program size
8-bit14-bit8-bit16-bitData bus Width