embeded_system

8/7/2019 Embeded_System

1/29

An embedded system can be defined as those control systems which aredesigned 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.


2/29

Important Units Ofmicroprocessor/controller

CPU:Central Processing Unit

I/O:Input /Output Bus: Address bus & Data bus Memory: RAM & ROM Timer I

nterrupt


3/29

Block Diagram of an Embedded System


4/29

Traffic LightDVD player

Digital clockMoving message display


5/29

CPU

General-PurposeMicro-

processor

RAM ROM I/O

Port

TimerSerialCOM

Port

Data Bus

Address Bus

General-Purpose Microprocessor System

CPU forComputers No RAM, ROM, I/O on CPU chip itself E

xample--Intel

s x86

:8086,8088,80386,80486,

Pentium

Many chips on mother board

General-purpose microprocessor


6/29

RAM ROM

I/OPort

TimerSerialCOMPort

Microcontroller

CPU

A smaller computer. On-chip RAM, ROM, I/O ports... Example:- Motorolas 6811, Intels 8051 and PIC

16X

A single chip

Microcontroller


7/29

Microprocessor CPU is stand-alone, RAM,

ROM, I/O, timer areseparate

designer can decide on theamount of ROM, RAM andI/O ports.

expensive general-purpose

Ex. 8085,8086 mp,Motorola 6800, Intels8086, etc.

Microcontroller

CPU, RAM, ROM, I/O andtimer are all on a singlechip

fix amount of on-chipROM, RAM, I/O ports

for applications in whichcost, power and space arecritical

single-purposeEx. 8051, PIC mc,Motorola MCs, Phillips,

etc.

Microprocessor v/s

Microcontroller


8/29


9/29

The 8051 Microcontroller: The 8051 is the first microcontroller of the MCS-51

family introduced by Intel Corporation at the end of the

1970s.

The 8051 family characteristics:o 4K Bytes ROMo 128 Bytes RAMo two timer/counters (16 bit)o A serial porto 32 input/output porto Interrupt controller


10/29

Microcontroller 8051 internal Architecture


11/29

Pin Description of the 8051

1

23

45

6

78

910

11

1213

1415

16

17

18

1920

40

3938

3736

35

3433

3231

30

2928

2726

25

24

23

2221

P1.0

P1.1P1.2

P1.3P1.4

P1.5

P1.6P1.7

RST(RXD)P3.0

(TXD)P3.1

(T

0)P

3.4(T1)P3.5

XTAL2

XTAL1GND

(INT0)P3.2

(INT1)P3.3

(RD)P3.7

(WR)P3.6

VccP0.0(AD0)

P0.1(AD1)

P0.2(AD2)P0.3(AD3)

P0.4(AD4)

P0.5(AD5)P0.6(AD6)

P0.7(AD7)

EA/VPPALE/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)

8051IC

8051


12/29

Vcc(+5volt)Pin - 40

Ground(0 volt)Pin-20

Pin Description


13/29

Pin Description

Port 0 fromPin-39 to pin-32

Used to excess bothdata & address

Dual functional


14/29

Microcontroller 8051Pin Description

Port 1 fromPin-1 to pin-8

Used as I/O port


15/29

Pin Description

Port 2 from

Pin-21 to pin-28

Used to excessaddress & as I/O port


16/29

Microcontroller 8051Pin Description

Port 3 fromPin-10 to Pin-17

P3.0 RXD

P3.1 TXD

P3.2 IN T0

P3.3 IN T1P3.4 T0

P3.5 T1

P3.6 WR

P3.7 RD


17/29

Pin Description

reset

crystal

External memory

Add. Latchenable

ProgramStore Enable


18/29

Addressing Modes

Immediate addressing modeso ADD A, #23h (Add immediate data to Acc)

Register addressing modeso ADD A, R2 (Add register to Accumulator)

Direct addressing modeso ADD A, 40h (Add data at location 40h to Accumulator)

RegisterIndirect addressing modeso

ADD A,@R2 (Add indirect RAM

to Acc)


19/29

Timers/counters

The 8051 has 2 timer/counter .They can be used either as timersto generate delay or as counters

to count events happening outsidethe controller.

o e.g., traffic light.


20/29

Timers/Counters

General 8051 has 2 timer:o Two 16-bit timero The counters are divided into two 8-Bit registers called the

timerlow (TL0, TL1) and high (TH0, TH1) bytes.o All counters action is controlled by bit states in the timer

mode control register (TMOD), the timer/counter controlregister (TCON), and certain program instructions.


21/29

TMOD Register:

Gate :It controls the way by which timer/counter willstart.

(set when gate is controlled by hardware)

C/T: Counter/Timer select bit.(set for counter)

M1 :Mode bit 1. M0 :Mode bit 0.


22/29

InterruptsDefinition of Interrupt

Event that disrupts the normal execution of aprogram and causes the execution of special

instructions


23/29

Interrupts

Program

time t


24/29

InterruptsInterrupt

Program

time t


25/29

Interrupts

Program

Interrupt Service Routine

Interrupt

Program

time t


26/29

Interrupts Internal orExternal Handling can be

enabled/disabled Prioritized

General 8051:o 3x timer interrupts,o 2x external interruptso 1x serial port interrupt


27/29


28/29

External Interrupts

Pins forexternalinterrupts

P3.2 IN T0

P3.3 INT

1


29/29

Smart card

ATM

Health card

Robotics

embeded_system

Documents