theory class 1dggfg

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Saturday, April 06, 2013

WELCOME




BASIC ELECTRICAL AND

ELECTRONIC COMPONENTS

• RESISTORS

• DIODES

• CAPACITORS

• INDUCTORS

• TRANSISTORS

• BATTERY

•

TRANSFORMER • VOLTAGE REGULATORS

• LDR (LIGHT DEPENDENT RESISTOR)

• RELAYS




The first band gives the first digit

The second band gives the second digit

The third band indicates the number of zeroes.

RESISTOR:

A resistor is a device which opposes the flow of

current. It is invented by OTIS F.BOYKIN in 1938.




Colour Number

Black 0

Brown 1

Red 2

Orange 3 Yellow 4

Green 5

Blue 6

Violet 7

Grey 8

White 9




DIODE:

A Diode is a two terminal electronic component that

conducts electric current only in one direction. It is

invented by William Henry Eccles in 1919.

Based on applications diodes are divided into two

types

-> PN junction

-> ZENER diode




PN junction diode:

The most common function of a diode is toallow an electric current in one direction (called

the forwarddirection) while blocking current in

the opposite direction (the reversedirection).




ZENER DIODE:

A Zener diode is a type of diode that permits current inthe forward direction like a normal diode, but also in the

reverse direction if the voltage is larger than the

breakdown voltage known as "Zener knee voltage" or

"Zener voltage".




LIGHT EMITTING DIODE (LED)

A light-emitting diode (LED) is a semiconductor light

source. LEDs are used as indicator lamps in many

devices, and are increasingly used for lighting.

k

A



In forward bias the led will be in on condition

and vice versa.

It takes 2 to 3 v of voltage and 10 to 20mamps

of current.





It is invented by Ewald George Von Kelisf. In

1745. Active Capacitors(low), Passive

Capacitors(high).

Capacitor block AC signals. capacitors

easily pass DC signals

CAPACITOR:



Types of Capacitors……


Electrolytic Capacitor

Film CapacitorDisk Capacitor




INDUCTOR:

• An inductor or a reactor can store energy in a

magnetic field created by the electric currentpassing through it. It is denoted in Henry.

• Typically an inductor is a conducting wire shaped

as a coil, the loops helping to create a strongmagnetic field inside the coil due to Faraday'sLaw of Induction.




TRANSISTORS:

A transistor is a semi conductor device commonly used

to amplify or switch electronic signals. A voltage orcurrent applied to one pair of the transistor's terminals

changes the current flowing through another pair of

terminals. Because the controlled (output) power can be

much more than the controlling (input) power, the

transistor provides amplification of a signal.



TRANSISTOR

• It is defined as Transfer of resistance and

for amplification purpose it is used.

• In the year 1947 at AT & T‟s BellLaboratories by JOHN Bardeen & Brattain

transistor is invented.





Transformer:



Transformer:

•Two types of transformers

Step up

Step down

• Transformer ratings

9-0-9

12-0-12

18-0-18





VOLTAGE REGULATOR:

• A voltage regulator is an electrical regulator designed

to automatically maintain a constant voltage level.

•

It may use an electromechanical mechanism, or passive or active electronic components. Depending

on the design, it may be used to regulate one or more

AC or DC voltages.




The voltage regulators are classified into two types.

positive series(7805)

negative series(7905)

7805

I/P GND O/P

7805SERIES Output

voltage

7905

I/P O/PGND




Light Dependent Resistor (LDR):

An LDR is an input transducer (sensor)which converts brightness (light) to

resistance. It is made from cadmium

sulphide (CdS) and the resistance

decreases as the brightness of lightfalling on the LDR increases.




RELAY:

A Relay is an electrically controllable switch widelyused in industrial controls, automobiles, etc…

inductor




OPERATION OF RELAY:

• The relay's switch connections are usually labeled COM,

NC and NO:• COM = Common, always connect to this, it is the

moving part of the switch.

• NC = Normally Closed, COM is connected to this whenthe relay coil is off.

• NO = Normally Open, COM is connected to this whenthe relay coil is on.

•

Connect to COM and NO if you want the switchedcircuit to be on when the relay coil is on.

• Connect to COM and NC if you want the switchedcircuit to be on when the relay coil is off.




N/C

COM

N/O

AC230V

Relay

I ND

U C T OR

IRON

ARM

ON

OFF

Diagrammatic explanation:




REGULATED POWER SUPPLY:




7812

7805

C1

C2

5V

12V

REGULATED POWER SUPPLY CIRCUIT

C

C=1000uF C1,C2=104pF R1,R2=330

R1

R2




RECTIFIER:

• The primary application of rectifiers is to drive usable

DC power from an AC supply. Virtually all electronics

except simple motor circuits such as fans require a DC

supply but mains power is AC so rectifiers find usesinside the power supplies of virtually all electronic

equipment.




FILTERS:

• Electronic filters are electronic circuits which

perform signal processing functions, specifically toremove unwanted frequency or voltage or currentcomponents from the signal, to enhance wantedones.

RECTIFIER

OUTPUT FILTER PURE DC

AC+DC DC

AC




How the Transistor act as a switch ?

what is a transistor?

A transistor is a semi conductor device commonlyused to amplify or switch electronic signals.




What is a switch? In electronics, a switch is an electrical component

that can break an electrical circuit, interrupting

the current or diverting it from one conductor to

another.




Transistor as a switch:

• Transistor can be used as an electronic switch, in

grounded-emitter configuration.

• Transistors are commonly used as electronic

switches, for both high power applicationsincluding switched mode power supply and low

power applications.

V




N/C

COM

N/O

LDR

100K

PRESET

Vcc

relay

330

LED

LIGHT VB<0.7V

T-OFF

NO

LIGHT

VB>0.7VT-ON

R

LOAD

Transistor as a switch

example



EMBEDDED SYSTEMS

MATLAB(Simulation)

VLSI(Simulation)


PROJECTS




1. First Embedded systems was introducedby CHARLES. Later on Students of MIT

University in the year 1961 in US.

2. Embedded Systems was First used for theproject MINITE MANE.9Processors Were

First Used for this project.

3. Embedded Systems is Divided into Two

Types

1. Simple E.S

2. Complex E.S




Embedded Systems

Simple

SystemsComplex

Systems

µp(1971) µc(1981)




•A uP•only is a single-chip CPU•bus is available•RAM capacity, num of port is selectable•RAM is larger than ROM (usually)

•A uC•contains a CPU and RAM,ROM ,Peripherals,I/O port in a single IC•internal hardware is fixed•Communicate by port•

ROM is larger than RAM (usually)•Small power consumption•Single chip, small board•Implementation is easy•Low cost

uP vs. uC




Company 4 bit 8 bit 16 bit 32 bit 64 bit

INTEL4004

4040

8008

8080

8085

8088/6

80186

80286

80386

80486

80860

PENTIUM

ZILOG Z80

Z8000

Z8001

Z8002

MOTOR

OLA

6800

6802

6809

68006

68008

68010

68020

68030

68040

History of Processors

E b dd d S t




Embedded SystemsBy Using the Software we are going to control

the operation of a hardware device.

Advantages:

•Automatic

•Power consumption

•Man power reduces

•Life time increases

•Efficiency increases

•Accurate In usage




• In general, "embedded system" is not a strictly

definable term, as most systems have some element of

extensibility or programmability.

• For example, handheld computers share some elements

with embedded systems such as the operating systems

and microprocessors which power them, but they allow

different applications to be loaded and peripherals to

be connected or a few dedicated functions", and is thus

appropriate to call "embedded".




Embedded system

• An embedded system is a special purpose computer

system designed to perform one or a few dedicatedfunctions, often with real time computing

constraints.

• It is usually embedded as part of a complete device

including hardware and mechanical parts.

• Since the embedded system is dedicated to specific

tasks, design engineers can optimize it, reducing the

size and cost of the product, or increasing the

reliability and performance.

• Embedded systems span all aspects of modern life.

Ch t i ti




Characteristics:

• Embedded systems are designed to do some

specific task, rather than be a general-purposecomputer for multiple tasks.

• Embedded systems are not always standalone

devices. Many embedded systems consist of small, computerized parts within a larger device

that serves a more general purpose.

• The program instructions written for embedded

systems are referred to as firmware, and arestored in read-only memory or Flash memory

chips.




Applications:

• Telecommunications• Consumer electronics like mp3 players, mobile

phones, digital cameras, DVD's, ovens, washing

machine, to control lights, to provide security,

climate, etc..




• A more sophisticated devices use graphical

screen with touch sensing or screen-edge

buttons provide flexibility while minimizing space

used. the meaning of the buttons can change

with the screen.




• Serial Communication Interfaces (SCI): RS-232,RS-422, RS-485 etc

• Synchronous Serial Communication Interface: I2C,

ESSI (Enhanced Synchronous Serial Interface)

• Universal Serial Bus (USB)

• Multi Media Cards (SD Cards, Compact Flash etc)

Peripherals




• Networks: Ethernet, Controller Area Network, Lan

networks, etc

• Timers: PLL(s), Capture/Compare and Time

Processing Units

• Analog to Digital/Digital to Analog (ADC/DAC)

• Debugging: JTAG, ISP, ICSP, BDM Port, BITP DP9

port …

Peripherals




• Embedded system means the processor is embeddedinto that application.

• An embedded product uses a microprocessor or

microcontroller to do one task only.

• In an embedded system, there is only one applicationsoftware that is typically burned into ROM.

• Example: printer, keyboard, video game player.

Overview of Embedded System




Contents

IntroductionBlock Diagram and PinDescription of the 8051

I/O Port Description

Led InterfacingSwitch Interfacing

Led And switch Interfacing

LCD Interfacing

Relay InterfacingADC Interfacing

Serial communication




Why do we need to learn

Microprocessors/controllers?

• The microprocessor is the core of computer

systems.

• Nowadays many communication, digital

entertainment, portable devices, are controlledby them.

• A designer should know what types of

components they needs, ways to reduce

production costs and product reliable.




Aspects of a microprocessor/controller

• Hardware :

Interfacing devices with the real world. Ex-LCD, LED, printers, keyboard etc.

• Software :

In order how to deal with inputs. By usingsoftware we can control the hardware to

obtain the desired outputs.




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

i (19 1)




CPU

General-

Purpose

Micro-

processor

RAM ROM I/O

PortTimer

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, Motorola‟s 680x0.

Many chips on mother board

General-purpose microprocessor:

Microprocessors(1971):

Microcontroller(1981):




RAM ROM

I/O

PortTimer

Serial

COM

PortMicrocontroller

CPU

• A smaller computer.

• On-chip RAM, ROM, I/O ports...

• Example: Motorola‟s 6811, Intel‟s8051, Zilog‟s Z8, PIC16X,ATMEL,AVR,ARM.

A single chip

Microcontroller(1981):




Microprocessor

• CPU is stand-alone,RAM, ROM, I/O,timer are separate

• designer can decideon the amount of ROM, RAM andI/O ports.

•Expansive,versatility.

• general-purpose

Microcontroller

• CPU, RAM, ROM, I/O

and timer are all on a

single chip

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

•

for applications inwhich cost, power and

space are critical

• single-purpose

Microprocessor vs. Microcontroller




1. Meeting the computing needs of the task efficientlyand cost effectively

• speed, the amount of ROM and RAM, the numberof 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 themicrocontrollers.

Three criteria in Choosing a

Microcontroller:




Block Diagram:

CPU

On-chip

RAM

On-chip

ROM for

program

code

4 I/O Ports

Timer 0

Serial

PortOSC

Interrupt

Control

External interrupts

Timer 1

Timer/Counter

Bus

Control

TxD RxDP0 P1 P2 P3

Address/Data

Counter

Inputs




Feature 8051 8052 8031

ROM (program space in bytes) 4K 8K 0K

RAM (bytes) 128 256 128

Timers 2 3 2I/O pins 32 32 32

Serial port 1 1 1

Interrupt sources 6 8 6

Comparison of the 8051 Family Members




4K Bytes On Chip ROM

128 bytes On Chip RAM

6 Interrupts

32 I/O channels

Bit Addressability

2 Timers

Features of 8051:

Other 8051 features




•only 1 On chip oscillator (external crystal)

•6 interrupt sources (2 external , 3 internal, Reset)

•64K external code (program) memory(only read)

•64K external data memory(can be read and write) by

RD,WR.

•Code memory is selectable by EA (internal or

external)

•We may have External memory as data memory and

code memory.

Other 8051 features

Comparison of the 8051 Family




ROM type8031 no ROM80xx mask ROM87xx EPROM89xx Flash EEPROM

89xx

8951895289538955898252891051

892051Example (AT89C51,AT89LV51,AT89S51)

AT= ATMEL(Manufacture)C = CMOS technologyLV= Low Power(3.0v) S=Flash Programming.

Comparison of the 8051 Family

Members

Comparison of the 8051




89XX ROM RAM TimerInt

Source IO pin Other8951 4k 128 2 6 32 -

8952 8k 256 3 8 32 -

8953 12k 256 3 9 32 WD

8955 20k 256 3 8 32 WD

898252 8k 256 3 9 32 ISP

891051 1k 64 1 3 16 AC

892051 2k 128 2 6 16 AC

Comparison of the 8051

Family Members

WD: Watch Dog Timer

AC: Analog Comparator

ISP: In System Programmable

Pi D i ti f th 8051




Pin Description of the 8051:

1

23

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

40

3938

37

36

35

34

33

32

31

30

29

28

27

26

25

24

23

22

21

P1.0

P1.1P1.2

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

PSENP2.7(A15)

P2.6(A14)

P2.5(A13)

P2.4(A12)

P2.3(A11)

P2.2(A10)

P2.1(A9)

P2.0(A8)

8051




8051

SchematicPin out




8051 Description:

Vcc, gnd and xtal:

• Vcc pin 40

– Vcc provides supply voltage to the chip.

– The voltage source is +5V.

• GND: pin 20 ground

• XTAL1 and XTAL2 pins 19,18




8051 Description:

• Reset: pin 9 reset

– It is an input pin and is active high normally low .

• The high pulse must be high at least 2 machine

cycles. – It is a power-on reset.

• Upon applying a high pulse to RST, the

microcontroller will reset and all values in

registers will be lost.• Reset values of some 8051 registers

Figure (b). Power-On RESET Circuit:




g ( )

30 pF

30 pF

8.2 K

10 uF

+

Vcc

11.0592 MHz

EA/VPP

X1

X2

RST

31

19

18

9

8051




0000DPTR 0007SP

0000PSW

0000B0000ACC

0000PC

Reset ValueRegister

RESET Value of Some 8051Registers:

RAM are all zero

SOME IMPORTANT PINS




PSEN (out): Program Store Enable, the read

signal for external program memory (active low).

ALE (out): Address Latch Enable, to latchaddress outputs at Port0 and Port2

EA (in): External Access Enable, active low toaccess external program memory locations 0 to4K

RXD,TXD: UART pins for serial I/O on Port 3

XTAL1 & XTAL2: Crystal inputs for internaloscillator.

SOME IMPORTANT PINS

Pi f 8051




Pins of 8051:

•

EA: pin 31 external access – There is no on-chip ROM in 8031 and 8032 .

– The EA pin is connected to GND to indicate the

code is stored externally.

– PSEN ALE are used for external ROM.

– For 8051, EA pin is connected to Vcc.

• PSEN: pin 29 program store enable

– This is an output pin and is connected to the OE

pin of the ROM.

Pins of 8051:




Pins of 8051:

• ALE: pin 30 address latch enable

– It is an output pin and is active high.

– 8051 port 0 provides both address and data.

– The ALE pin is used for de-multiplexing the

address and data by connecting to the G pin of the 74LS373 latch.

• I/O port pins

– The four ports P0, P1, P2, and P3.

– Each port uses 8 pins.

– All I/O pins are bi-directional.




Address Multiplexing

for External Memory

Accessingexternal

codememory

Pins of I/O Port:




Pins of I/O Port:

• The 8051 has four I/O ports

– Port 0: pins 32-39, P0 P0.0-P0.7 – Port 1: pins 1-8 , P1 : P1.0-P1.7

– Port 2: pins 21-28, P2 : P2.0-P2.7

– Port 3: pins 10-17, P3 : P3.0-P3.7

– Each port has 8 pins.• P0.X ,X=0,1,...,7, P1.X, P2.X, P3.X

• Ex: P0.0 is the bit 0, LSB of P0

• Ex: P0.7 is the bit 7, MSB of P0

• These 8 bits form a byte.

• Each port can be used as input or output (bi-direction).




Other Pins:

• P1, P2, and P3 have internal pull-up resisters.

– P1, P2, and P3 are not open drain.

• P0 has no internal pull-up resistors and does not

connects to Vcc inside the 8051. – P0 is open drain.

• However, for a programmer, it is the same toprogram P0, P1, P2 and P3.

• All the ports upon RESET are configured asoutput.




Port 0 with Pull-Up Resistors:

Pull-up resistors are used in electronic logic circuits to

ensure that inputs to logic systems settle at expected logic

levels if external devices are disconnected.

Pull-up resistors may also be used at the interface

between two different types of logic devices, possibly

operating at different power supply voltages.

Pull Up Resistors




P0.0P0.1

P0.2P0.3P0.4P0.5P0.6P0.7

DS5000

8751

8951

Vcc

10 K

P

or t

0

Pull-Up Resistors

P 3 Al F i




Port 3 Alternate Functions:

17RDP3.7

16WR P3.615T1P3.5

14T0P3.4

13INT1P3.3

12INT0P3.2

11TxDP3.1

10RxDP3.0

PinFunctionP3 Bit




ADDRESSING MODES:

There are five addressing modes available in the8051:

• Register

• Direct

• Indirect

• Immediate

• Indexed

REGISTER ADDRESSING




REGISTER ADDRESSING:

• 8051 has access to eight working registers (R0

to R7)

• Some instructions are specific to a certain

register, such as the accumulator etc.

Example: ADD A,R7Example: MUL AB




Direct Addressing: •

Direct addressing is so-named because thevalue to be stored in memory is obtained by

directly retrieving it from another memory

location.

Example: MOV A,30h




Indirect Addressing:

• In 8051 assembly language, indirect addressing is

represented by an @ before R0 or R1.

Example: MOV A, @R0

Moves a byte of data from internal RAM atlocation whose address is in R0 to the

accumulator.




Immediate Addressing:

• In assembly language, immediate operands are

preceded by #.

• Operand my be a numeric constant, a symbolic

variable or an arithmetic expression using

constants, symbols and operators.

Example: MOV A,#12




Indexed Addressing:

• Indexed addressing uses a base register (either the

program counter or data pointer) and an offset

(the accumulator) in forming the effective address

for a JMP or MOVC instruction.

Example: MOVC A, @A+DPTR

On-Chip Memory



On-Chip Memory

Internal RAM

Register Banks




Active bank selected by PSW[RS1,RS0] bit

Permits fast “context switching” in interrupt service routines (ISR).

Register Banks

Registers F R i t



Registers

0706050403020100

R7R6R5R4R3R2R1R0

0F

08

17

10

1F

18

Bank 3

Bank 2

Bank 1

Bank 0

Four RegisterBanks

Each bank hasR0-R7

Bit Addressable Memory



Bit Addressable Memory

20h – 2Fh (16

locations X 8-bits

= 128 bits)

7F 78

1A

10

0F 08

07 06 05 04 03 02 01 00

27

26

25

24

23

22

21

20

2F

2E

2D

2C

2B

2A

29

28

Bit addressing:

mov a, 1Ahor

mov a, 23h.2

Special Function Registers



Special Function Registers

DATA registers

CONTROL registersTimersSerial portsInterrupt systemAnalog to Digital converterDigital to Analog converter

Addresses 80h – FFh

Direct Addressing used toaccess SFRs



8051 CPU Registers



•A (Accumulator)•B•PSW (ProgramStatus Word)•

SP (StackPointer)•PC (ProgramCounter)•DPTR (Data Pointer)

Used inassembler

instructions

Registers



Registers

A

B

R0

R1

R3

R4

R2

R5

R7

R6

DPH DPL

PC

DPTR

PC

Some 8051 16-bit Register

Some 8-bit Registers

of the 8051



The 8051

Assembly Instructions

Overview



Overview

• Data transfer instructions

• Data processing (arithmetic and logic)

• Program flow instructions or BranchingInstructions

• Addressing modes

Data Transfer Instructions



Data Transfer Instructions

• MOV dest, source dest source• Stack instructions

PUSH byte ;increment stack pointer,

;move byte on stack

POP byte ;move from stack to byte,;decrement stack pointer

• Exchange instructionsXCH a, byte ;exchange accumulator and byte

XCHD a, byte ;exchange low nibbles of;accumulator and byte

Addressing Modes



Addressing Modes

Immediate Mode – specify data by its value

mov A, #0 ;put 0 in the accumulator

;A = 00000000

mov R4, #11h ;put 11hex in the R4

register

;R4 = 00010001

mov B, #11 ;put 11 decimal in b register;B = 00001011

mov DPTR,#7521h ;put 7521 hex in DPTR

;DPTR = 0111010100100001

Addressing Modes



Addressing Modes

Register Addressing – either source ordestination is one of CPU register

MOV R0,A

MOV A,R7

ADD A,R4

ADD A,R7

MOV DPTR,#25F5H

MOV R5,DPL

MOV R3,DPH

Note that MOV R4,R7 is incorrect

Addressing Modes



Addressing ModesDirect Mode – specify data by its 8-bit

addressUsually for 30h-7Fh of RAM

Mov a, 70h ; copy contents of RAM at 70h to a

Mov R0,40h ; copy contents of RAM at 40h to R0

Mov 56h,a ; put contents of a at 56h

Addressing Modes



Addressing Modes

Direct Mode – play with R0-R7 by directaddress

MOV A,4 MOV A,R4

MOV A,7 MOV A,R7

MOV 7,2 MOV R7,R2 Invalid instruction

MOV R2,#5 ;Put 5 in R2

MOV R2,5 ;Put content of RAM at 5 in R2

Addressing Modes



Addressing Modes

Register Indexed Mode – source ordestination address is the sum of the base

address and the accumulator(Index)

• Base address can be DPTR or PC mov dptr, #4000h

mov a, #5

movc a, @a + dptr ;a M[4005]

SFRs Address



All SFRs such as( ACC, B, PCON, TMOD, PSW, P0~P3, …)

are accessible by name and direct

address

But

both of theseMust be coded as direct address

Stacks



Stacks

pushpop

stack

stack pointer

Go do the stack exercise…..



Data Processing Instructions

Arithmetic Instructions

Logic Instructions





• Add

• Subtract

• Increment• Decrement

• Multiply

• Divide

• Decimal adjust




Mnemonic Description

ADD A, byte add A to byte, put result in A

ADDC A, byte add with carry

SUBB A, byte subtract with borrow

INC A increment AINC byte increment byte in memory

INC DPTR increment data pointer

DEC A decrement accumulator

DEC byte decrement byte

MUL AB multiply accumulator by b register

DIV AB divide accumulator by b register

DA A decimal adjust the accumulator

ADD Examples



a p es

mov a, #3Fh

add a, #D3h • What is the value of theC, AC, OV flags after thesecond instruction isexecuted?

0011 11111101 0011

0001 0010 C = 1

AC = 1OV = 0

Increment and Decrement



• The increment and decrement instructions do NOT affect the Cflag.

• Notice we can only INCREMENT the data pointer, notdecrement.

INC A increment A

INC byte increment byte in memory

INC DPTR increment data pointer

DEC A decrement accumulator

DEC byte decrement byte

Logic Inst ctions



Logic Instructions

Bitwise logic operations

(AND, OR, XOR, NOT)

Clear

Rotate

Swap

Logic instructions do NOT affect the flags in PSW

Bitwise Logic



g

ANL AND

ORL OR

XRL XOR

CPL Complement

Examples:

0000111110101100ANL

00001111

10101100ORL

00001111

10101100XRL

10101100CPL

00001100

10101111

10100011

01010011

Other Logic Instructions



g

CLR - clear

RL – rotate left

RLC – rotate left through CarryRR – rotate right

RRC – rotate right through

CarrySWAP – swap accumulator nibbles

CLR ( Set all bits to 0)



CLR A

CLR byte (direct mode)

CLR Ri (register mode)CLR @Ri (register indirect mode)

Rotate



• Rotate instructions operate only on a

RL a

Mov a,#0xF0 ; a 11110000

RR a ; a 11100001

RR a Mov a,#0xF0 ; a 11110000

RR a ; a 01111000

Swap



p

SWAP a

mov a, #72h ; a 72h

swap a ; a 27h

Bit Logic Operations



•Some logic operations can be used with single bitoperands

ANL C, bit

ORL C, bit

CLR CCLR bit

CPL C

CPL bit

SETB C

SETB bit

• “bit” can be any of the bit-addressable RAM locations orSFRs.

Program Flow Control



• Unconditional jumps (“go to”)

• Conditional jumps

• Call and return

Unconditional Jumps



•SJMP <rel addr> ; Short jump,

relative address is 8-bit 2’s complement number,

so jump can be up to 127 locations forward, or 128

locations back.

•LJMP <address> ; Long jump

• AJMP <address> ; Absolute jump to

anywhere within 2K block of program memory

•JMP @A + DPTR ; Long indexed jump

Infinite Loops



p

Start: mov C, p3.7

mov p1.6, C

sjmp Start

Microcontroller application programs are almost always infinite loops!

Conditional Jump



• These instructions cause a jump to occur only if acondition is true. Otherwise, program executioncontinues with the next instruction.

loop: mov a, P1jz loop ; if a=0, goto loop,

; else goto next instruction

mov b, a

• There is no zero flag (z)

• Content of A checked for zero on time

Conditional jumps



j p

Mnemonic DescriptionJZ <rel addr> Jump if a = 0

JNZ <rel addr> Jump if a != 0

JC <rel addr> Jump if C = 1

JNC <rel addr> Jump if C != 1

JB <bit>, <rel addr> Jump if bit = 1

JNB <bit>,<rel addr> Jump if bit != 1

JBC <bir>, <rel addr> Jump if bit =1, &clear

bitCJNE A, direct, <rel addr> Compare A and memory,

jump if not equal

Example: Conditional Jumps



if (a = 0) is truesend a 0 to LED

else

send a 1 to LED

More Conditional Jumps



Mnemonic Description

CJNE A, #data <rel addr> Compare A and data, jump

if not equal

CJNE Rn, #data <rel addr> Compare Rn and data,

jump if not equalCJNE @Rn, #data <rel addr> Compare memory and data,

jump if not equal

DJNZ Rn, <rel addr> Decrement Rn and then

jump if not zero

DJNZ direct, <rel addr> Decrement memory and

then jump if not zero

Call and Return



• Call is similar to a jump, but – Call pushes PC on stack before branching

acall <address ll> ; stack

PC; PC address 11 bit

lcall <address 16> ; stack PC

; PC address 16 bit

Return



• Return is also similar to a jump, but

– Return instruction pops PC from stack to getaddress to jump to

ret ; PC stack

Subroutines



Main: ...

acall sublabel

...

...

sublabel: ...

...

ret

the subroutine

call to the subroutine

Why Subroutines?



• Subroutines allow us to have "structured"assembly language programs.

• This is useful for breaking a large designinto manageable parts.

• It saves code space when subroutines can

be called many times in the sameprogram.

Timer Delay Calculation for



XTAL = 11.0592 MHz(a) in hex

• (FFFF – YYXX + 1) × 1.085 s

• where YYXX are TH, TL initial values respectively.

•Notice that values YYXX are in hex.

(b) in decimal

• Convert YYXX values of the TH, TL register to

decimal to get a NNNNN decimal number • then (65536 – NNNNN) × 1.085 s




LED (Light Emitting Diode):

• Light-emitting diodes are elements for light

signalization in electronics.

• They are manufactured in different shapes, colors and

sizes.• Low price, low consumption and simple use

• These LED‟s are used for indication purpose i.e., ON

& OFF.

Symbol of LED:




Symbol of LED:

Some different colors of LED:

http://commons.wikimedia.org/wiki/File:LED_symbol.svg




Some different colors of LED:

How to interface LED with

http://en.wikipedia.org/wiki/File:RBG-LED.jpg




microcontroller ?

• Anode is connected through a resistor to Vcc &

the Cathode is connected to the Microcontroller

pin.

• So when the Port Pin is HIGH the LED is OFF &

when the Port Pin is LOW the LED is turned ON.




Can we connect like this?




• When the port Pin is HIGH the Anode is positivewith respect to the Cathode so the LED should

http://knol.google.com/k/-/-/189gpauady45g/btt8fb/ledinterfacing1.jpg




pturn ON right?

• But the internal pull-up resistor comes in serieswith the resistor thus limiting the current flowingthrough the LED. This current is not sufficient

enough to Turn ON the LED.

A Simple Program to glow an LED:




A Simple Program to glow an LED:

ORG 0000HCLR P1.0 //Turn ON LED

CLR P1.1

CLR P1.2END

A program using port to glow an LED :




A program using port to glow an LED :

ORG 0000H

MOV p1,#OOH //Copy P1 to A

END

A program to ON &OFF the LED:




CASE1:ORG 0000H

MOV P1,#OFFHMOV P1,#OOH

END

CASE 2:




CASE 2:

ORG 0000H

MOV P1,#OFFH

MOV A,P1

CPL A //ComplimentMOV P1,A

END




SWITCH INTERFACING




An electrical switch is any device used to interrupt

the flow of electrons in a circuit. Switches areessentially binary devices: they are eithercompletely on ("closed") or completely off ("open").

• CPU accesses the switches through ports.Therefore these switches are connected to amicrocontroller. This switch is connected between

the supply and ground terminals.

• These switches are connected to an input port.

Vcc




P2.1R

GND

Interfacing switch with the microcontroller

8

0

5

1

Thus now the two conditions are to beremembered:




• When the switch is open, i.e., when not pressed the

total supply i.e., Vcc appears at the port pin P2.0

P2.0 = 1

• When the switch is closed i.e., when it is pressed,

the total supply path is provided to ground. Thusthe voltage value at the port pin P2.0 will be zero.

P2.0 = 0

Vcc




P2.1

R

GND

Interfacing Led And Switch with the Microcontroller

8

0

5

1

Vcc

P1.0




Liquid crystal display (LCD):

• A liquid crystal display (LCD) is a thin flat panel




• A liquid crystal display (LCD) is a thin, flat panel

used for electronically displaying information such

as text, images, and moving pictures.

• Its uses include monitors for computers,

televisions, instrument panels, and other devices

ranging from aircraft cockpit displays, to every-day consumer devices such as gaming devices,

clocks, watches, calculators, and telephones.

• Among its major features are its lightweight

construction its portability and its ability to be




construction, its portability, and its ability to be

produced in much larger screen sizes than are

practical for the construction of cathode ray tube

(CRT) display technology.

Why we are using LCD ?




• Its low electrical power consumption enables it tobe used in battery-powered electronic equipment.

It is an electronically-modulated optical device

made up of any number of pixels filled with liquid

crystals and arrayed in front of a light source

(backlight) or reflector to produce images in color

or monochrome.

Pin Description of LCD:




1. Ground2. Vcc +5V

3. Contrast control

4. Register select (RS)5. Read/Write (RD/WR)

6. Enable (EN)

7 – 14 pins all are data pins D0 – D7

15. Vcc +5V }

16. Ground }For backlight purpose

RS (register select):

The register select pin is used for the selection of the required register either data or command




the required register either data or commandregister

If RS=0 ; command register is selected

If RS=1 ; data register is selected

R/W (read or write):

This pin is for the selection of read or write modeIf R/W=0 ; write mode is selected

If R/W=1 ; read mode is selected

EN (enable):• Enable pin is a active high to low pin used for

writing the data to the LCD.

LCD COMMAND CODES:




• 01 Clear display screen

• 06 Increment cursor

• 38 2lines and 5 by 7 matrix

• 80 Force cursor to beginning of 1st line

• 0E Display on, cursor blinking

• C0 Force cursor to beginning 0f 2nd line

LCD INTERFACING WITH MICROCONTROLLER:




P0.0P0.1P0.2

P0.3

P0.4

P0.5

P0.6

P0.7

D0

D1

D2

D3

D4

D5

D6

D7RS R/W E

P2.0

P2.1

P2.2

Vss

Vee

Vss

10k

POT

8

0

51

LCD

GND

How To Send Commands To LCD:




COMMAND:

CLR RS

CLR R/W

SETB EN

CLR EN

How to send Data to LCD:




DATA:

SETB RS

CLR R/W

SETB EN

CLR EN

A Simple Program Of LCD:




ORG OOH

MOV A,#38H

ACALL COMMAND

MOV A,#0EH

ACALL COMMAND

MOV A,# ‟H‟

ACALL DATA

MOV A,# „I‟

ACALL DATA

COMMAND : CLR RSCLR R/W

SETB EN




SETB EN

CLR ENRET

DATA:

SETB RSCLR R/W

SETB EN

CLR EN

RET

END




Relay Interfacing With

Microcontroller




Relay: It can be defined as an electrical switch that opens

and closes under the control of another electrical circuit.

The switch is operated by an electromagnet to open or

close one or more of contacts. A relay is able to control an

output circuit of higher power than the input circuit.Relays are devices which allow low power circuits to

switch a relatively high Current/Voltage ON/OFF.

For a relay to operate a suitable pull-in & holding current

should be passed through its coil.

Generally relay coils are designed to operate from a

particular voltage often its 5V or 12V.

Types:

There are many types of relays which are as

f ll




follows:

SPDTDPDT

Symbol Of Relay:

Advantages of relays:

• R l it h AC d DC t i t




• Relays can switch AC and DC, transistors

can only switch DC.• Relays can switch high voltages, transistors

cannot.

• Relays are a better choice for switchinglarge currents (> 5A).

• Relays can switch many contacts at once.

Disadvantages Of Relay:




• Relays are bulkier than transistors for

switching small currents.

• Relays cannot switch rapidly , transistors

can switch many times per second.

• Relays use more power due to the current

flowing through their coil.

SPDT Relay (Single Pole Double Throw) :

An electromagnetic switch, consist of a coil , 1




g , ,

common terminal , 1 normally closed terminal ,

and one normally open terminal.

When the coil of the relay is at rest (not

energized), the common terminal and thenormally closed terminal have continuity. When

the coil is energized, the common terminal and the

normally open terminal have continuity.

DPDT (Double Pole Double Throw):

• Can be used to isolate float switches from spiking




voltage or excessive current.

• Avoids risk that spiking pump voltage will hurt

float switches.

Specifications:

• Coil voltage: 12VDC

• Coil resistance: 160 Ohms

• Contact rating: 10A at 250VAC or 30VDC.

Why do I want to use a relay and do I really

need to?




• The coil of an SPDT relay that we most commonly

use draws very little current (less than 200

milliamps) and the amount of current that you can

pass through a relay's common, normally closed,and normally open contacts will handle up to 30 or

40 amps. This allows you to switch devices such as

headlights, parking lights, horns, etc.,

SPDT & DPDT:




Relay Interfacing with the Microcontroller:




1 U 16

2 L 15

3 N 14

4 2 13

5 8 12

6 0 11

7 3 10

8 9

RELAY LOAD

Ground Vcc

AT 89S52

P1.0

ULN2003 CURRENT DRIVER:

• The ULN2003 current driver is a high voltage, high




g g , g

current Darlington arrays each containing seven

open collector Darlington pairs with common

emitters. Each channel is rated at 500mA and can

withstand peak currents of 600mA.

ULN DRIVER CIRCUIT




This ULN2003 driver can drive seven relays at a

time. The pins 8 and 9 provide ground and Vcc

respectively.

Working Of ULN Driver:




• It can accept seven inputs at a time and produces

seven corresponding outputs. If the input to any

one of the seven input pins is high, then the value

at its corresponding output pin will be low, forexample if the input at pin 6 is high, then the value

at the corresponding output i.e., output at pin 11

will be low. Similarly if the input at a particular

pin is low, then the corresponding output will behigh.

• Thus for the output to be low, the input applied at

that corresponding input pin should be high. The

input to the ULN driver is provided by the




input to the ULN driver is provided by the

microcontroller. Thus the instruction required tooperate the relay through the microcontroller is

SETB PX.Y

• Where X is the port number (P0, P1, P2

and P3).

• And Y is the pin number of Port X.

Applications:




• To control a high-voltage circuit with a low-

voltage signal

• To control a high-current circuit with a low-

current signal,• To detect and isolate faults on transmission and

distribution lines by opening and closing circuit

breakers.

RS232




To ensure fast and reliable data transmission

between two devices

In RS232 it consists of 9 pins but we generally

use only three pins 2,3 and 5 namely TXD RXD

GND respectively.

MAX232To convert TTL or CMOS voltages to RS232

voltages, and vice versa




voltages, and vice versa

Complementary metal – oxide – semiconductor

(CMOS)

CMOS uses complementary and symmetrical

pairs of p-type and n-type metal oxide

semiconductor field effect transistors (MOSFET‟s)

for logic functions.

Two important characteristics of CMOS devicesare high noise immunity and low static power

consumption.

TTL (Transistor transistor logic)




• TTL integrated circuits were a standard method

of construction for the processors of mini-

computer and mainframe processors

• Transistor – transistor logic (TTL) is a class of digital circuits built from bipolar junction

transistors (BJT) and resistors. It is called

transistor – transistor logicbecause both the logic

gating function (e.g., AND) and the amplifyingfunction are performed by transistors

MAX232



MAX 232 INTERFACING WITH MICRO

CONTROLLER




13514TxD0(P3.1)

RxD0(P3.0)

11 1110 12

23

8

0

5

1

M

A

X

2

3

2

DB

9 GND




ANALOG TO DIGITAL CONVERTER

• Analog-to-digital converters are among the most




Analog-to-digital converters are among the most

widely used devices for data acquisition. Digitalsystems use binary values, but in the physical world

everything is continuous i.e., analog values.

Temperature, pressure (wind or liquid), humidity

and velocity are the physical analog quantities.

• These physical quantities are to be converted into

digital values for further processing. Thus, an

analog-to-digital converter is needed to convert

these electrical signals into digital values so that the

microcontroller can read and process them.

ADC0804:

• The ADC chip that is used in this project is




The ADC chip that is used in this project is

ADC0804. The ADC0804 IC is an 8-bit parallelADC in the family of the ADC0800 series from

National Semiconductor. It works with +5 volts

and has a resolution of 8 bits. In the ADC0804, the

conversion time varies depending on the clockingsignals applied to the CLK IN pin, but it cannot be

faster than 110µs.

PIN Diagram of ADC




Pin description of ADC

CS (Chip selection):




Chip select is a active low input used to activatethe ADC 0804.

RD (read):

This is also a active low pin used to get theconverted data out of the ADC 0804.

WR (write):

This is also active low used to inform the ADC tostart the conversion process.

CLK IN & CLK R:

CLK IN is connected to external clock whenexternal clock is used and if internal clock is used




both clocks are connected to capacitor and aresistor.

INTR (INTERRUPT):

It is an active low output pin using for stop theconversion.

Vin(+) & Vin(-):

Vin(+) is used for the conversion of analog todigital by connecting Vin(-) to the ground.

Vcc:It is the +5v power supply to the chip.

Vref/2:

Pi 9 i d f th f lt If d




Pin 9 is used for the reference voltage. If we need

the input range 0-4V, Vref/2 is connected to 2V.D0-D7:

These are the digital data output pins.

D7 is the MSB.Analog ground & Digital ground:

Analog ground is connected to ground of analogVin while taking the inputs in the same way digital

ground is also used for the digital outputs.

ADC INTERFACE WITH MICROCONTROLLER

89C51




89C51

P2.4P2.5P2.6

P2.7P1.7P1.6

P1.5P1.4P1.3P1.2

P1.1P1.0

Keypads are a part of HMI or Human Machine Interface and

play really important role in a small embedded system where

KEYPAD INTERFACING




play really important role in a small embedded system where

human interaction or human input is needed. Matrix keypadsare well known for their simple architecture and ease of

interfacing with any microcontroller.

Interfacing the Keyboard to the 8051

At the lowest level, keypads are organized in a matrix of rows

and columns. The CPU accesses both rows and column

through ports; therefore, an 4*4 matrix of keys can be

connected to a microprocessor. When a key pressed, a row andcolumn make a connect; otherwise, there is no connection

between row and column.

Constructing a Matrix Keypad:

Construction of a keypad is really simple. As per the

outline shown in the figure below we have four rows and




outline shown in the figure below we have four rows and

four columns. In between each overlapping row andcolumn line there is a key.keeping this outline we can

construct a keypad using simple SPST Switches as

shown below:

Consider an example

Row4-row1 = 1110




Row4-row1 1110

Col4-col1 = 1011

That means the row 1 and the col 3 intersected i.e.

sw3 is pressed.




What is communication?




• Communication is nothing but sharing of data or

transferring the data from one system to another.

system1 system2

Types of communication:




In Serial communications means informationis transmitted from source to destination over a

single pathway.

In Parallel Communication, often 8 or more

lines are used to transfer data to a device that isonly a few feet.

COMPUTERS TRANSFER DATA INTWO WAYS:




Sender Receiver Sender Receiver

Serial Transfer Parallel Transfer

D0-D7D0

Other control lines

Other control lines

Why we prefer serial transmission

over parallel transmission?




• In Parallel data transfers, often 8 or more lines

are used to transfer data to a device that is only

a few feet.

• Where as serial transmission uses only singleline to transmit the same data over long

distances

• There are chances of loosing data in parallel

communication rather than in serial

communication.

Simplex vs. Duplex Transmission




• Simplex transmission: the data can sent in onedirection.

– Example: the computer only sends data to the

printer.

• Duplex transmission: the data can be transmitted

and received.

Transmitter Receiver

Transmitter

Receiver Receiver

Transmitter

Half vs. Full Duplex




• Half duplex: if the data is transmitted one way at

a time.

• Full duplex: if the data can go both ways at the

same time. Two wire conductors for the data lines.

Transmitter

Receiver

Receiver

Transmitter

Transmitter

Receiver

Receiver

Transmitter

RxD and TxD pins in the 8051



• TxD pin 11 of the 8051 (P3.1)

• RxD pin 10 of the 8051 (P3.0)

SBUF register MOV SBUF,#’D’ ;load SBUF=44H, ASCII for

‘D’

MOV SBUF,A ;copy accumulator intoSBUF

MOV A,SBUF ;copy SBUF into

accumulator

Registers Used in Serial Transfer Circuit




• SBUF (Serial data buffer)

• SCON (Serial control register)

• TMOD (Timer mode register)

SBUF




• This is an 8-bit register used for serial

communication in 8051.For a byte of data to be

transferred it must be placed in sbuf register and

in similar way sbuf holds the data when it isreceived.

SCON Register (serial control)

It used to program the start bit, stop bit and data




SM0 SM1 SM2 REN TB8 RB8 TI RI

It used to program the start bit, stop bit and data

bits of data framing

SM0 , SM1:These two bits determine the framing of data by

specifying the number of bits per character, and

the start and stop bits.

SM0 SM1

0 0 Serial Mode 0




0 0 Serial Mode 0

0 1 Serial Mode 1, 8-bit data, 1 stop bit,

1 start bit

1 0 Serial Mode 2

1 1 Serial Mode 3

RECEIVE - Data receive through the RXD pin startsupon the two following conditions are met: bit REN=1

and RI=0

(both of them are stored in the SCON register) When all




(both of them are stored in the SCON register). When all

8 bits have been received, the RI bit of the SCON register

is automatically set indicating that one byte receive is

complete.

TRANSMIT - Data transmit is initiated by writing data

to the SBUF register. In fact, this process starts after any

instruction being performed upon this register. When all

8 bits have been sent, the TI bit of the SCON register isautomatically set.

Serial control (SCON) Register

SM0 RITIRB8TB8RENSM2SM1



SM0 (SCON.7) : mode specifier

SM1 (SCON.6) : mode specifier

SM2 (SCON.5) : used for multi processor communication

REN (SCON.4) : receive enable (by software enable/disable)

TB8 (SCON.3) : transmit bit8

RB8 (SCON.2) : receive bit 8

TI (SCON.1) : transmit interrupt flag set by HW clear by SWRI (SCON.0) : receive interrupt flag set by HW clear by SW

SM0 RITIRB8TB8RENSM2SM1

TMOD




• TMOD is an 8 bit register in which the lower 4 bits

are set aside for Timer0 and the upper 4 bits for

Timer1.

GATE C/T M0 M1 GATE C/T M1 M0

TMOD -Timers

Bit Number Type Working Timer Type

7 GATE1Gating Control when

1




7 GATE1g

set1

6 C/T1

To decide whether

timer is used as a

delay generator or

as an event counter

1

5 M1 Timer mode bit 1


3 GATE0Gating Control

Purpose0

2 C/T0

To decide whether

timer is used as a

delay generator or

as an event counter

0



Gate

E ti h f t ti d t i



•Every timer has a mean of starting and stopping.

– GATE=0

• Internal control

• The start and stop of the timer are controlled by way of software.

• Set/clear the TR for start/stop timer. – GATE=1

• External control

• The hardware way of starting and stopping the timer bysoftware and an external source.

• Timer/counter is enabled only while the INT pin is high and theTR control pin is set (TR).

M1, M0

• M0 and M1 select the timer mode for timers 0 & 1.



0 0 0 13-bit timer mode

8-bit THx + 5-bit TLx (x= 0 or 1)

0 1 1 16-bit timer mode

8-bit THx + 8-bit TLx

1 0 2 8-bit auto reload

8-bit auto reload timer/counter;

THx holds a value which is to be reloaded into

TLx each time it overflows.1 1 3 Split timer mode

Example 9-3

Find the value for TMOD if we want to program timer 0 in mode 2,



use 8051 XTAL for the clock source, and use instructions to startand stop the timer.

Solution:

TMOD= 0000 0010 Timer 1 is not used.

Timer 0, mode 2,

C/T = 0 to use XTAL clock source (timer)

gate = 0 to use internal (software)

start and stop method.

timer 1 timer 0

Timer modes



Timers /Counters Programming

• The 8051 has 2 timers/counters: timer/counter 0 and



timer/counter 1. They can be used as1. The timer is used as a time delay generator.

– The clock source is the internal crystal frequency of the 8051.

2. An event counter.

– External input from input pin to count the number of eventson registers.

– These clock pulses could represent the number of peoplepassing through an entrance, or the number of wheel rotations,or any other event that can be converted to pulses.

C/T (Clock/Timer)



• This bit is used to decide whether thetimer is used as a delay generator or anevent counter.

• C/T = 0 : timer

• C/T = 1 : counter

Registers Used in Timer/Counter



• TH0, TL0, TH1, TL1• TMOD (Timer mode register)

• TCON (Timer control register)

• Since 8052 has 3 timers/counters, theformats of these control registers are

different. – T2CON (Timer 2 control register), TH2 and TL2

used for 8052 only.

Basic Registers of the Timer



• Both timer 0 and timer 1 are 16 bits wide.

– These registers stores

• the time delay as a timer

• the number of events as a counter

– Timer 0: TH0 & TL0

• Timer 0 high byte, timer 0 low byte

– Timer 1: TH1 & TL1• Timer 1 high byte, timer 1 low byte

– Each 16-bit timer can be accessed as twoseparate registers of low byte and high byte.

Timer Registers



D15 D8D9D10D11D12D13D14 D7 D0D1D2D3D4D5D6

TH0 TL0

D15 D8D9D10D11D12D13D14 D7 D0D1D2D3D4D5D6

TH1 TL1

Timer 0

Timer 1

Power control register



Power control



• A standard for applications where powerconsumption is critical

• two power reducing modes

– Idle

– Power down

Idle mode

• An instruction that sets PCON.0 causes Idle mode– Last instruction executed before going into the Idle mode



– Last instruction executed before going into the Idle mode

– the internal CPU clock is gated off

– Interrupt, Timer, and Serial Port functions act normally.

– All of registers , ports and internal RAM maintain their data duringIdle

– ALE and PSEN hold at logic high levels

• Any interrupt – will cause PCON.0 to be cleared by HW (terminate Idle mode)

– then execute ISR

– with RETI return and execute next instruction after Idle instruction.

• RST signal clears the IDL bit directly

Power-Down Mode

• An instruction that sets PCON 1 causes power dowm mode



• An instruction that sets PCON.1 causes power dowm mode

• Last instruction executed before going into the power downmode

• the on-chip oscillator is stopped.

• all functions are stopped,the contents of the on-chip RAMand Special Function Registers are maintained.

• The ALE and PSEN output are held low

• The reset that terminates Power Down

Power control example



Org 0000hLjmp main

Org 0003h

Orl pcon,#02h ;power down mode

Reti

Org 0030h

Main:

……

……

……

Orl pcon,#01h ;Idle mode

end



BAUD RATE


Baud Rates in the 8051:

• Baud rate is the number of signal changes per




second• The 8051 transfers and receives data serially at

many different baud rates by using UART.

• UART divides the machine cycle frequency by 32

and sends it to Timer 1 to set the baud rate.• Signal change for each roll over of timer 1.

XTAL

oscillator ÷ 12

÷ 32

By UART

Machine cycle

frequency28800 Hz

To timer 1

To set the

Baud rate

921.6 kHz

11.0592 MHz

Timer 1



Interrupts andInterrupt

Programming


Interrupts Programming

• An interrupt is an external or internal event that



interrupts the microcontroller to inform it that a deviceneeds its service.

Interrupts vs. Polling

• A single microcontroller can serve several devices. • There are two ways to do that:

– interrupts

– polling.

• The program which is associated with the interrupt iscalled the interrupt service routine (ISR) orinterrupt handler .

Steps in executing an interrupt

• Finish current instruction and saves the PC on stack.



• Jumps to a fixed location in memory depend on type of interrupt

• Starts to execute the interrupt service routine until RETI

(return from interrupt)

• Upon executing the RETI the microcontroller returns tothe place where it was interrupted. Get pop PC fromstack

Interrupt Sources

• Original 8051 has 6 sources of



Original 8051 has 6 sources of interrupts – Reset – Timer 0 overflow – Timer 1 overflow – External Interrupt 0 – External Interrupt 1 – Serial Port events (buffer full, buffer empty, etc)

• Enhanced version has 22 sources

– More timers, programmable counter array, ADC, moreexternal interrupts, another serial port (UART)

Interrupt Vectors

Each interrupt has a specific place in code memory where



Each interrupt has a specific place in code memory whereprogram execution (interrupt service routine) begins.

External Interrupt 0: 0003h

Timer 0 overflow: 000Bh



Serial : 0023h

Timer 2 overflow(8052+) 002bh

Note: that there are

only 8 memory

locations between

vectors.

SJMP main

ORG 03H

ISRs and Main Program in8051



ljmp int0sr ORG 0BH

ljmp t0sr

ORG 13H

ljmp int1sr

ORG 1BH

ljmp t1sr

ORG 23H

ljmp serialsr

ORG 30H

main:

…

END

Interrupt Enable (IE) register

All interrupt are disabled after resetWe can enable and disable them bye IE



Enabling and disabling aninterrupt

by bit operation



Recommended in the middle of programSETB EA ;Enable All

SETB ET0 ;Enable Timer0 ovrf

SETB ET1 ;Enable Timer1 ovrf

SETB EX0 ;Enable INT0

SETB EX1 ;Enable INT1

SETB ES ;Enable Serial port

by mov instructionRecommended in the first of program

MOV IE, #10010110B

SETB IE.7

SETB IE.1

SETB IE.3

SETB IE.0

SETB IE.2SETB IE.4

Example

• A 10khz square wave with 50% duty cycle



ORG 0 ;Reset entry poitLJMP MAIN ;Jump above interrupt

ORG 000BH ;Timer 0 interrupt vector

T0ISR:CPL P1.0 ;Toggle port bit

RETI ;Return from ISR to Main program

ORG 0030H ;Main Program entry point

MAIN: MOV TMOD,#02H ;Timer 0, mode 2

MOV TH0,#-50 ;50 us delay

SETB TR0 ;Start timer

MOV IE,#82H ;Enable timer 0 interrupt

SJMP $ ;Do nothing just wait

END

Example



• Write a program using interrupts tosimultaneously create 7 kHz and 500 Hzsquare waves on P1.7 and P1.6.

71s143s

1ms

2ms

P1.7

P1.6

8051

143s8051

SolutionORG 0

LJMP MAIN

ORG 000BH

LJMP T0ISR

ORG 001BH

LJMP T1ISR



71s

1ms

2ms

P1.7

P1.6

ORG 0030H MAIN: MOV TMOD,#12H

MOV TH0,#-71

SETB TR0

SETB TF1

MOV IE,#8AH

MOV IE,#8AHSJMP $

T0ISR: CPL P1.7

RETI

T1ISR: CLR TR1

MOV TH1,#HIGH(-1000)

MOV TL1,#LOW(-1000)

SETB TR1CPL P1.6

RETI

END

Timer ISR



• Notice that – There is no need for a “CLR TFx” instruction

in timer ISR

– 8051 clears the TF internally upon jumping

to ISR

• Notice that

– We must reload timer in mode 1

– There is no need on mode 2 (timer autoreload)

External interrupt type control• By low nibble of Timer control register TCON

• IE0 (IE1): External interrupt 0(1) edge flag.



– set by CPU when external interrupt edge (H-to-L) is detected. – Does not affected by H-to-L while ISR is executed(no int on int)

– Cleared by CPU when RETI executed.

– does not latch low-level triggered interrupt

• IT0 (IT1): interrupt 0 (1) type control bit. – Set/cleared by software

– IT=1 edge trigger

– IT=0 low-level trigger

TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0

Timer 1 Timer0 for Interrupt

(MSB) (LSB)

External Interrupts



IE0

(TCON.3)

0003

INT0

(Pin 3.2) 0

1

2

IT0

Edge-triggered

Level-triggered (default)

IE1

(TCON.3)

INT0

(Pin 3.3) 0

1

2

IT1

Edge-triggered

Level-triggered (default)

0013

Example of external interuuptORG 0000H

LJMP MAIN ;



;interrupt service routine (ISR);for hardware external interrupt INT1;

ORG 0013H

SETB P1.1

MOV R0,200

WAIT: DJNZ R0,WAIT

CLR P1.1

RETI;

;main program for initialization;

ORG 30H

MAIN: SETB IT1 ;on negative edge of INT1

MOV IE,#10000100B

WAIT2: SJMP WAIT2

END

Example of external interuupt



Example of external interuuptOrg 0000h

Ljmp main



Org 0003h x0isr: clr p1.7

Reti

Org 0013h

x1isr: setb p1.7

Reti

Org 0030h

Main: mov ie,#85h

Setb it0

Setb it1

Setb p1.7

Jb p3.2,skip

Clr p1.7

Skip: Sjmp $

end

Interrupt Priorities• What if two interrupt sources interrupt at the same

time?



• The interrupt with the highest PRIORITY gets servicedfirst.

• All interrupts have a power on default priority order.

1. External interrupt 0 (INT0)2. Timer interrupt0 (TF0)

3. External interrupt 1 (INT1)

4. Timer interrupt1 (TF1)

5. Serial communication (RI+TI)

• Priority can also be set to “high” or “low” by IP reg.

Interrupt Priorities (IP) Register

--- PX0PT0PX1PT1PSPT2---



IP.7: reserved

IP.6: reserved

IP.5: timer 2 interrupt priority bit(8052 only)

IP.4: serial port interrupt priority bit

IP.3: timer 1 interrupt priority bit

IP.2: external interrupt 1 priority bit

IP.1: timer 0 interrupt priority bitIP.0: external interrupt 0 priority bit

Interrupt Priorities Example




• MOV IP , #00000100B or SETB IP.2 gives priority order

1. Int1

2. Int0

3. Timer0

4. Timer1

5. Serial

• MOV IP , #00001100B gives priority order

1. Int1

2. Timer1

3. Int04. Timer0

5. Serial

Interrupt inside an interrupt




A high-priority interrupt can interrupta low-priority interrupy

All interrupt are latched internally

Low-priority interrupt wait until 8051has finished servicing the high-priority interrupt

Interrupts

mov a, #2

mov b, #16



mul ab mov R0, a

mov R1, b

mov a, #12

mov b, #20

mul abadd a, R0

mov R0, a

mov a, R1

addc a, b

mov R1, aend

P r o gr am Ex e c u

t i on

interruptISR: inc r7

mov a,r7

jnz NEXT

cpl P1.6

NEXT: reti

return

Interrupt Sources

Original 8051 has 5 sources of



• interrupts – Timer 0 overflow

– Timer 1 overflow

– External Interrupt 0

– External Interrupt 1 – Serial Port events (buffer full, buffer empty, etc)

• Enhanced version has 22 sources

– More timers, programmable counter array, ADC, moreexternal interrupts, another serial port (UART)

Interrupt Process

f fl f h



If interrupt event occurs AND interrupt flag for that event isenabled, AND interrupts are enabled, then:

1. Current PC is pushed on stack.

2. Program execution continues at the interrupt vector

address for that interrupt.3. When a RETI instruction is encountered, the PC is

popped from the stack and program executionresumes where it left off.

Interrupt Priorities

h f



• What if two interrupt sources interrupt atthe same time?

• The interrupt with the highest PRIORITY

gets serviced first.• All interrupts have a default priority order.

• Priority can also be set to “high” or “low”.

Interrupt SFRs



Global Interrupt Enable

– must be set to 1 for anyinterrupt to be enabled

Interrupt enables for the 5 original 8051 interrupts:

Timer 2

Serial (UART0)

Timer 1

External 1

Timer 0External 0

1 = Enable

0 = Disable

Interrupt Vectors

Each interrupt has a specific place in code memory where

ti (i t t i ti ) b i



program execution (interrupt service routine) begins.





Serial : 0023h

Timer 2 overflow(8052+) 002bh

Note: that there are

only 8 memory

locations between

vectors.

Interrupt Vectors

To avoid overlapping Interrupt Service routines, it ist t JUMP i t ti t th t dd



common to put JUMP instructions at the vector address.This is similar to the reset vector.

org 009B ; at EX7 vector

ljmp EX7ISR

cseg at 0x100 ; at Main program

Main: ... ; Main program

...

EX7ISR:... ; Interrupt service routine

... ; Can go after main program

reti ; and subroutines.

theory class 1dggfg

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