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By: Ritesh Maheshwari
3rd
Yr student of Electronics Instr. & Control Engg.
Spring 2007
��In the name of God��
GIT Student Of EIC Branch Presents:
Seminar On

Embedded Systems
?What is an Embedded System?
?Where are Embedded Systems used?
?Typical Embedded Systems Hardware
?Embedded OS and Software
?Why study Embedded System?
?Microprocessors
?Microcontrollers
?The 8051 Microcontroller
?A simple project using AT89C51
?References

Block Diagram of an Embedded System

? A specialized computer system that is part of a larger system or machine.
? Typically, an embedded system is housed on a single microprocessor board
with the programs stored in ROM.
? Virtually all appliances that have a digital interface -- watches, microwaves,
VCRs, cars -- utilize embedded systems.
? Some embedded systems include an operating system, but many are so
specialized that the entire logic can be implemented as a single program.

?It is specially designed to perform a few tasks in the most
efficient way.
?Interacts with physical elements in our environment viz.,
controlling & driving a motor, sensing temperature etc. i.e.
�� An embedded system can
be defined as those control systems which are
designed either by microprocessor or microcontroller
for a specific tasks. ��
OR
�� An embedded system is
some combination of computer hardware & software,
either fixed in capability or programmable, that is
specifically designed for a particular kind of application
device. ��

Where are Embedded Systems used?
?Signal processing systems
? Real-time video, DVD players, Medical equipment.
?Distributed control
? Network routers, switches, firewalls, mass transit systems, Elevators
?��Small�� systems
? Mobile phones, pagers, home appliances, toys, smartcards, MP3 players,
PDAs, digital cameras, sensors, pc keyboard & mouse
?Modern cars: Up to 100 or more processors
? Engine control unit
? ABS systems (Anti Lock Brake systems)
? Emissions control
? Diagnostics and Security systems
? Accessories (doors, windows etc)

EMBEDDED SYSTEM IN DAILY LIFE
Washing machine
cell phone
microWave oven
sensor based Washbasin

Traffic lighTdvd player
digiTal clock
moving message display

Typical Embedded Systems Hardware
?Commercial off-the-shelf components (COTS)
? e.g. wireless radios, sensors, I/O devices
? Cheap
?Application-Specific ICs (ASICs)
? ICs tailored to meet application needs
? Good performance for their intended task(s)
? Original ESs were ASICs only
?Domain-specific processors
? DSPs
? Microcontrollers
?Microprocessors
? General Purpose Processors

Embedded Operating Systems:
?Office-style OSes
? PalmOS
? WindowsCE
?RTOSes
? VxWorks
? QNX
?Linux
? Linux is already ubiquitous
? Hundreds of different devices are using it
? http://www.linuxdevices.com/articles/AT4936596231.html
? Numerous commercial + open source products
?Mobile OS
? Symbian
?Others
? TinyOS

Why Study Embedded Systems?
? Embedded systems are playing important roles in our livesEmbedded systems are playing important roles in our lives
every day, even though they might not necessarily be visible.every day, even though they might not necessarily be visible.
? Some of the embedded systems we use every day control theSome of the embedded systems we use every day control the
menu system on television, the timer in a microwave oven, a cellmenu system on television, the timer in a microwave oven, a cell
phone, an MP3 player or any other device with some amount ofphone, an MP3 player or any other device with some amount of
intelligence built-in.intelligence built-in.
? In fact, recent poll data shows that embedded computerIn fact, recent poll data shows that embedded computer
systems currently outnumber humans in the USA.systems currently outnumber humans in the USA.
? Embedded systems is a rapidly growing industry where growthEmbedded systems is a rapidly growing industry where growth
opportunities are numerous.opportunities are numerous.

CPU
General-
Purpose
Micro-
processor
RAM ROM I/O
Port
Timer
Serial
COM
Port
Data Bus
Address Bus
General-Purpose Microprocessor System
?CPU for Computers
?No RAM, ROM, I/O on CPU chip itself
?Example--Intel��s x86: 8086,8088,80386,80486, Pentium
?Motorola��s 680x0: 68000, 68010, 68020,68030,6040
Many chips on mother board
General-purpose microprocessor

Microprocessor
?A microprocessor is a programmable digital electronic
component that incorporates the functions of a central
processing unit (CPU) on a single semiconducting integrated
circuit (IC).
?The prime use of a microprocessor is to read data, perform
extensive calculations on that data, and store those
calculations in a mass storage device or display the results for
human use.
?The programs used by the microprocessors are stored in the
mass storage device & loaded into RAM as the user directs.

RAM ROM
I/O
Port
Timer
Serial
COM
Port
Microcontroller
CPU
?A smaller computer.
?On-chip RAM, ROM, I/O ports...
?Example:- Motorola��s 6811, Intel��s 8051 and PIC 16X
A single chip
Microcontroller

Microcontroller
?An embedded microcontroller is a microcomputer that
contains most of its peripherals & required memory inside
a single integrated circuit along with the CPU.
?They have a high concentration of on-chip facilities such
as serial ports, parallel input/output ports, timers,
counters, interrupt control, analog-to-digital converters,
random access memory, read only memory, etc.
?The prime use of a microcontroller is to control the
operation of a machine using fixed program that is stored
in ROM & that does not change over the lifetime of the
system.

Microcontroller
? Uses:
1. Microcontrollers have become common in many areas, and
can be found in home appliances, computer equipment, and
instrumentation.
2. They are often used in automobiles, and have many industrial
uses as well, and have become a central part of industrial
robotics.
3. Because they are usually used to control a single process and
execute simple instructions, microcontrollers do not require
significant processing power.

? Uses conti��..
4. Microcontrollers are hidden inside a surprising
number of products these days.
5. If your microwave oven has an LED or LCD screen
and a keypad, it contains a microcontroller.
6. All modern automobiles contain at least one
microcontroller. The engine is controlled by a
microcontroller, as are the anti-lock brakes, the cruise
control and so on..

1. Meeting the computing needs of the task efficiently and cost
effectively
? speed, the amount of ROM and RAM, the number of I/O
ports and timers, size, packaging, power consumption
? easy to upgrade
? cost per unit
2. Availability of software development tools
? assemblers, debuggers, C compilers, emulator, simulator,
technical support
3. Wide availability and reliable sources of the microcontrollers.
Three criteria in Choosing a Microcontroller

The necessary tools for a
microprocessor/controller
?CPU: Central Processing Unit
?I/O: Input /Output
?Bus: Address bus & Data bus
?Memory: RAM & ROM
?Timer
?Interrupt
?Serial Port
?Parallel Port

Why do we need to learn
Microprocessors/controllers?
?The microprocessor is the core of computer
systems.
?Nowadays many communication, digital
entertainment, portable devices, are
controlled by them.
?A designer should know what types of
components he needs, ways to reduce
production costs and product reliable.

Microprocessor
?CPU is stand-alone, RAM,
ROM, I/O, timer are
separate
?designer can decide on the
amount of ROM, RAM and
I/O ports.
?expansive
?versatility
?general-purpose
?Ex. 8085,8086 mp, Motorola
6800, Intel��s 8086, etc.
Microcontroller
? CPU, RAM, ROM, I/O and
timer are all on a single chip
? fix amount of on-chip ROM,
RAM, I/O ports
? for applications in which cost,
power and space are critical
? single-purpose
? Ex. 8051, PIC mc, Motorola
MC��s, Phillips, etc.
Microprocessor v/s Microcontroller

The 8051 Microcontroller:
?The 8051 is the first microcontroller of the MCS-51 family
introduced by Intel Corporation at the end of the 1970��s.
?The 8051 family characteristics:
?4K Bytes ROM
?128 Bytes RAM
?two timer/counters (16 bit)
?A serial port
?4 general purpose parallel input/output port
?Interrupt controller
The 8051 can address 64K of external data memory and
64K of External program memory.

Microcontroller 8051 internal Architecture

Pin Description of the 8051
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
40
39
38
37
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
RST
(RXD)P3.0
(TXD)P3.1
(T0)P3.4
(T1)P3.5
XTAL2
XTAL1
GND
(INT0)P3.2
(INT1)P3.3
(RD)P3.7
(WR)P3.6
Vcc
P0.0(AD0
)P0.1(AD1)
P0.2(AD2
)P0.3(AD3)
P0.4(AD4)
P0.5(AD5)
P0.6(AD6)
P0.7(AD7)
EA/VPP
ALE/PROG
PSEN
P2.7(A15)
P2.6(A14)
P2.5(A13)
P2.4(A12)
P2.3(A11)
P2.2(A10)
P2.1(A9)
P2.0(A8)
8051
IC
? 8051 other family members:
1. 8751 (has EPROM)
2. 8951 (has EEPROM)

Vcc(+5volt)
Pin - 40
Ground(0 volt)
Pin-20
Pin
DescriPtion

Pin Description
Port 0 from
Pin-39 to pin-32
Used to excess
both
data & address
Dual functional

Microcontroller 8051
Pin Description
Port 1 from
Pin-1 to pin-8
Used as I/O port

Pin DescriPtion
Port 2 from
Pin-21 to pin-28
Used to excess
address & as I/O port

Microcontroller 8051
Pin DescriPtion
Port 3 from
Pin-10 to Pin-17
P3.0
RXDP3.1
TXDP3.2 IN T0
P3.3 IN T1
P3.4 T0
P3.5
T1P3.6 WR
P3.7 RD

Pin Description
reset
crystal
EA for
external memory
EA=0

Addressing Modes
?Immediate addressing modes
?Register addressing modes
?Direct addressing modes
?Register Indirect addressing modes
?Indexed addressing modes

Timers/Counters
?A timer is a counter that is increased with every time an
instruction is executed e.g. 8051 with 12MHz increases a
counter every 1.085 ?s
?General 8051 has 3 timer:
?Two 16-bit timer
?One 16-bit timer with extra-functionality (introduced with
the 8052)
?The counters are divided into two 8-Bit registers called the
timer low (TL0, TL1) and high (TH0, TH1) bytes.
?All counters action is controlled by bit states in the timer
mode control register (TMOD), the timer/counter control
register (TCON), and certain program instructions.

Timers/counters
?Timer: measures time intervals
?To generate timed output events
? e.g., hold traffic light green for 10 s
?To measure input events
? e.g., measure a car��s speed
?Based on counting clock pulses
? E.g., let Clk period be 10 ns
? And we count 20,000 Clk pulses
? Then 200 microseconds have passed
? 16-bit counter would count up to 65,535*10
ns = 655.35 microsecond., resolution = 10 ns
? Top: indicates top count reached, wrap-
around
16-bit up
counter
Clk
Cnt
Basic timer
Top
Reset
16

Counters
?Counter: like a timer, but
counts pulses on a general
input signal rather than clock
?e.g., count cars passing over a
sensor
?Can often configure device as
either a timer or counter
16-bit up
counter
Clk
16
Cnt_in
2x1
mux
Mode
Timer/counter
Top
Reset
Cnt

TMOD Register:
?Gate : When set, timer only runs while INT(0,1) is high.
?C/T : Counter/Timer select bit.
?M1 : Mode bit 1.
?M0 : Mode bit 0.

?TF1: Timer 1 overflow flag.
?TR1: Timer 1 run control bit.
?TF0: Timer 0 overflag.
?TR0: Timer 0 run control bit.
?IE1: External interrupt 1 edge flag.
?IT1: External interrupt 1 type flag.
?IE0: External interrupt 0 edge flag.
?IT0: External interrupt 0 type flag.

Crystal
11.0592
MHZ
/12
Timer
Freq.
TH0 TL0 TF0
TRO
1.085 ?S
? In this the delay produced is calculated as:
DELAY= 1.085?Sec X (NO. OF COUNTS)

Block Diagram
8051
S
E
N
S
O
R
��???��???
40
PIN
DIP
A
D
C
LCD
DISPLAY
D A C
��???��???
��???��???
��???��???
LEDS
4 SWITCHES
REAL TIME
CLOCK
4��4 MATRIX KEYBOARD

? We can Interfaced a number of modules
such as
? LED and 7-segment Display
? LCD
? Keyboard
? Real Time Clock (RTC)
? DAC
? ADC
? Sensors
? EEPROM
? RS-232

Light Emitting diode
?It is single light display that include incandescent
and are treated as single binary points to be
switched off and on by program instructions
.
?It has two pins, first is connected to port and
second one is grounded (vss).
?It requires a high logic to glow from the port pin.

0RG 0000H
HERE: CLR
P1.0
SJMP HERE
END

?Seven-segment displays commonly contain LED
segments which arranged as an 8 with a common
lead (cathode or anode) and 7 individual leads for
each segment.
?Block Diagram shows a common cathode type of
segment
?In common cathode to lit a segment a high input
logic is required.
?In common anode to lit a segment a low input logic
is required.

Interfacing of 7-segment with 8051
^^^^^^
^^^^^^
^^^^^^
^^^^^^
^^^^^^
^^^^^^
^^^^^^
^^^^^^
^^^^^^
P0.0
P0.2
P0.1
P0.3
P0.4
P0.5
P0.6
P0.7
8051
^^^^^^
Vcc Vcc

LCD
?It is an Intelligent Alphanumeric display which can
be used to display numbers, characters, and graphics.
?It has 14 pins as shown in pin diagram.
?Display contains 2 internal byte wide registers, one
for command (RS=0) and one for display (RS=1).
?There are certain commands to be send to the Lcd
for making some setting such as clear screen, force
the cursor to home position and blink the cursor.
?R/W pin is set to 1 for reading and to 0 for writing.
?EN pin is set to 1 for enabling display.
?DB0-DB7 are pins for 8-bit data bus.

Interfacing LCD with 8051
8051
^^^^^^
4��16 Character LCD Display
E RS R/W VeeGnd Vcc
+5v
10k
D0
D7
P1.0
P1.7
P2.0
P2.1
P2.2

Interrupts
Definition of ��Interrupt��
��Event that disrupts the normal execution of a
program and causes the execution of special
instructions��

Interrupts
Interrupt
Program
time t

Interrupts
Program
Interrupt Service Routine
Interrupt
Program
time t

Interrupt Handling
?Code that deals with
interrupts: Interrupt
Handler or Interrupt
Service Routines (ISRs)
Address space in
code space

Interrupt OverheadsInterrupt arrives
Complete current instruction
Save essential register information
Vector to ISR
Save additional register information
Execute body of ISR
Restore other register information
Return from interrupt and restore essential
registers
Resume task
Interrupt
Latency
Interrupt
Termination

Interrupts
?Internal or External
?Handling can be
enabled/disabled
?Prioritized
?General 8051:
?3x timer interrupts,
?2x external interrupts
?1x serial port interrupt

External Interrupts
Pins for
external interrupts

Interrupt Flags?Bits that are set if
the interrupt occurs

Summary: Interrupts?Definition of ��Interrupt��:
Event that disrupts the normal execution
of a program and causes the execution of
special instructions
?Handling can be enabled/disabled
?Prioritized
?Internal or External
?External Interrupts:
?Level-triggered
?Edge-triggered
?8051: 3 timer interrupts, 2 external
interrupts & a serial port interrupt
threshold
Level-triggered
Edge-triggered
trigger point
trigger point
t
t

? In this project we try to give the same prototype for this type of trains.
?The train is designed for three stations, named as Jaipur railway station,
Sitapura & GIT College.
? The stoppage time is of 3 sec & time between two consecutive stations is 6
sec.
? There are indicators, which are used to show the train direction i.e. UP path &
Down path.
? Before stopping at station the train blows the buzzer.
? It also includes an emergency brake system due to which the train stops as
soon as the brakes are applied and resumes journey when the emergency situation
is over.
? The coding of the metro train prototype is given in the assembly language.

Why we choose this project ?
?Our approach is to gain knowledge of Interfacing different
devices with Microcontroller for useful applications and to
fulfill the Hardware Module requirement of college
authorities.
?This is such a project which can be used to perform any
kind of application depend on the modules which are
interfaced.
?These leads us to Microcontroller Based Embedded
System.

Applications
?By interfacing STEPPER MOTOR with Microcontroller, we
can make the trainer kit which controls the motion of
train.
?We can also generate various types of waves such as
square, triangular and saw tooth in accordance with the
programme fed in 8051, 89c51, etc. chip.
?Initially we interfaced LED, 7-segment and Keyboard and
check programme which is the purpose of trainer Kit.
?In these way we go step by step for each module interface
and accomplish the goal of making a well-functioning
Trainer Kit.
?Finally we will add some features by interfacing Sensors

Smart card
ATM
Health card
Robotics

Touch sensitive stairs
Automatic gates
Accelerator

Conclusion
?Future aspect of embedded
technologies
?Experience during training
?Importance of this training
program

References
?www.wikipedia.com
?www.webcomtechnologiesusa.com
?www.worldbook.com
?www.usahem.com
?www.quasarelectronics.com
?www.electronicsforu.com
?www.nationalsemiconductor.com
?www.embeddedforu.com
?www.google.com

At the End ��
?Thanks for your Attention ��. ;)
Ritesh Maheshwari
Amardeep Pandey
Pankaj Chaudhary
Akhilesh Pandey
Monsoon 2007

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