microprocessor & microcontroller 8086,8051 notes

Presented byC.GOKUL,AP/EEE

Velalar College of Engg & Tech, ErodeEmail: gokulvlsi@gmail.com

EC6504Microprocessor & Microcontroller

DEPARTMENTS: ECE {semester 05}CSE,IT {semester 04}

Regulation : 2013 ANNA UNIVERSITY Syllabus

syllabus

BOOK ReferencesMain Book: 1. Microprocessors and Interfacing, Programming and Hardware by

Doughlas V.HallOther Authors:

2. Microcomputer Systems: The 8086 / 8088 Family -Architecture, Programming and Design by Yu-Cheng Liu, Glenn A.Gibson

3. INTEL Microprocessors 8086/8088, 80186/80188, 80286, 80386, 80486, Pentium, Prentium ProProcessor, Pentium II, III, 4 by Barry B. Bery

4. Advanced microprocessor and peripherals by A K RAY

LOCAL AUTHOR: 8086 Microprocessor by Nagoor Kani => Unit 1,2,3

8051 Microcontroller by V Udayashankara => Unit 4,5

NPTEL Lecture Materials References

• Microprocessor and Peripheral Devices by Dr. Pramod Agarwal , IIT Roorkee

Link: http://nptel.ac.in/courses/108107029/

• Microprocessors and Microcontrollers by Prof. Krishna Kumar IISc Bangalore

Link: http://nptel.ac.in/courses/106108100/

Microprocessor Basics

• Microprocessor (µP) is the “brain” of a computer that has been implemented on one semiconductor chip.

• The word comes from the combination micro and processor.

• Processor means a device that processes whatever(binary numbers, 0’s and 1’s)

To process means to manipulate. It describes all manipulation.

Micro - > extremely small

Definition of a Microprocessor.

The microprocessor is a programmable device that takes in numbers, performs on them arithmetic or logical operations according to the program stored in memory and then produces other numbers as a result.

Microprocessor ?

A microprocessor is multi programmable clock driven

register based semiconductor device that is used to fetch ,

process & execute a data within fraction of seconds.

Applications

• Calculators• Accounting system• Games machine• Instrumentation• Traffic light Control• Multi user, multi-function environments• Military applications• Communication systems

MICROPROCESSOR HISTORY

DIFFERENT PROCESSORS AVAILABLE

Socket

Processor

Pinless Processor

Slot Processor

ProcessorSlot

Development of Intel Microprocessors

• 8086 - 1979• 286 - 1982• 386 - 1985• 486 - 1989• Pentium - 1993• Pentium Pro - 1995• Pentium MMX -1997• Pentium II - 1997• Pentium II Celeron - 1998• Pentium II Zeon - 1998• Pentium III - 1999• Pentium III Zeon - 1999• Pentium IV - 2000• Pentium IV Zeon - 2001

GENERATION OF PROCESSORS

Processor Bits Speed

8080 8 2 MHz

8086 16 4.5 – 10 MHz

8088 16 4.5 – 10 MHz

80286 16 10 – 20 MHz

80386 32 20 – 40 MHz

80486 32 40 – 133 MHz

GENERATION OF PROCESSORS

Processor Bits Speed

Pentium 32 60 – 233 MHz

Pentium Pro

32 150 – 200 MHz

Pentium II, Celeron ,

32 233 – 450 MHz

Pentium III, Celeron

, Xeon

32 450 MHz –1.4 GHz

Pentium IV, Celeron ,

32 1.3 GHz –3.8 GHz

Itanium 64 800 MHz –3.0 GHz

Intel 4004 Introduced in 1971.

It was the first microprocessor by Intel.

It was a 4-bit µP.

Its clock speed was 740KHz.

It had 2,300 transistors.

It could execute around 60,000 instructions per second.

Intel 4040

Introduced in 1971.

It was also 4-bit µP.

8-bit Microprocessors

Intel 8008

Introduced in 1972.

It was first 8-bit µP.

Its clock speed was 500 KHz.

Could execute 50,000 instructions per second.

Intel 8080

Introduced in 1974.

Its clock speed was 2 MHz.

Intel 8085 Introduced in 1976.

Its data bus is 8-bit and address bus is 16-bit.

Could execute 7,69,230 instructions per second.

It could access 64 KB of memory.

It had 246 instructions.

16-bit Microprocessors

INTEL 8086 Introduced in 1978.

Its clock speed is 4.77 MHz, 8 MHz and 10 MHz, depending on the version.

Could execute 2.5 million instructions per second.

It could access 1 MB of memory.

It had 22,000 instructions.

It had Multiply and Divideinstructions.

It was created as a cheaper version of Intel’s 8086.

It was a 16-bit processor with an 8-bit external bus.

INTEL 80186 & 80188 Introduced in 1982.

They were 16-bit µPs.

Clock speed was 6 MHz.

80188 was a cheaper version of 80186 with an 8-bit external data bus.

It was 16-bit µP.

It could address 16 MB of memory.

It had 1,34,000 transistors.

32-BIT MICROPROCESSORS

It could address 4 GB of memory.

It had 2,75,000 transistors.

Its clock speed varied from 16 MHz to 33 MHz depending upon the various versions. 27

It had 1.2 million transistors.

Its clock speed varied from 16 MHz to 100 MHz depending upon the various versions.

8 KB of cache memory was introduced.

INTEL PENTIUM Introduced in 1993.

It was originally named 80586.

INTEL PENTIUM PRO

Introduced in 1995.

It had 21 million transistors.

Cache memory:

8 KB for instructions.

8 KB for data.

INTEL PENTIUM II Introduced in 1997.

Its clock speed was 233 MHz to 500 MHz.

Could execute 333 million instructions per second.

INTEL PENTIUM II XEON

Introduced in 1998.

It was designed for servers.

Its clock speed was 400 MHz to 450 MHz.

INTEL PENTIUM III Introduced in 1999.

Its clock speed varied from 500 MHz to 1.4 GHz.

It had 9.5 million transistors.

INTEL PENTIUM IV Introduced in 2000.

Its clock speed was from 1.3 GHz to 3.8 GHz.

It had 42 million transistors.

INTEL DUAL CORE Introduced in 2006.

It is 32-bit or 64-bit µP.

64-BIT MICROPROCESSORS

Intel Core 2 Intel Core i3

INTEL CORE I5 INTEL CORE I7

Basic Terms• Bit: A digit of the binary number { 0 or 1 }• Nibble: 4 bit Byte: 8 bit word: 16 bit• Double word: 32 bit • Data: binary number/code operated by an

instruction• Address: Identification number for memory

locations• Clock: square wave used to synchronize various

devices in µP• Memory Capacity = 2^n ,

n->no. of address lines

BUS CONCEPT• BUS: Group of conducting lines that carries data ,

address & control signals.CLASSIFICATION OF BUSES:1.DATA BUS: group of conducting lines that carries

data.2. ADDRESS BUS: group of conducting lines that

carries address.3.CONTROL BUS: group of conducting lines that

carries control signals {RD, WR etc}CPU BUS: group of conducting lines that directly

connected to µPSYSTEM BUS: group of conducting lines that carries

data , address & control signals in a µP system41

TRISTATE LOGIC3 logic levels are:• High State (logic 1) • Low state (logic 0)• High Impedance state

High Impedance: output is not being driven to any defined logic level by the output circuit.

Basic Microprocessors System

InputDevices

Processing Data into

InformationOutput Devices

Control Unit

Secondary Storage Devices

Arithmetic-Logic Unit

Primary Storage Unit

Central Processing Unit

Keyboard,Mouseetc

MonitorPrinter

Disks, Tapes, Optical Disks

THE 8086 MICROPROCESSOR

UNIT 1 Syllabus• Introduction to 8086 • Microprocessor architecture • Addressing modes• Instruction set • Assembler directives• Assembly language programming • Modular Programming

1.Linking and Relocation 2.Stacks , Procedures , Macros

• Interrupts and interrupt service routines• Byte & String Manipulation. 45

8086 Microprocessor-introduction

INTEL launched 8086 in 19788086 is a 16-bit microprocessor with

• 16-bit Data Bus {D0-D15}• 20-bit Address Bus {A0-A19} [can access upto

2^20= 1 MB memory locations] .It has multiplexed address and data bus

AD0-AD15 and A16–A19.It can support upto 64K I/O ports

8086 Microprocessor It provides 14, 16-bit registers.8086 requires one phase clock with a 33%

duty cycle to provide optimized internal timing.

– Range of clock:• 5 MHz for 8086• 8Mhz for 8086-2• 10Mhz for 8086-1

8086 Internal Architecture 8086 employs parallel processing 8086 CPU has two parts which operate at the

same time• Bus Interface Unit• Execution Unit

CPU functions1. Fetch

2. Decode3. Execute

8086 CPU

Bus Interface Unit (BIU)

Execution Unit(EU)

Bus Interface Unit

Sends out addresses for memory locationsFetches Instructions from memoryReads/Writes data to memorySends out addresses for I/O portsReads/Writes data to Input/Output ports

Execution Unit

Tells BIU (addresses) where to fetch instructions or dataDecodes & Executes instructions

Dividing the work between BIU & EU speeds up processing

Architecture Diagram of 8086

STACK POINTER (SP)

BASE POINTER (BP)

SOURCE INDEX (SI)

DESTINATION INDEX (DI)

EXTRA SEGMENT (ES)

CODE SEGMENT (CS)

STACK SEGMENT (SS)

DATA SEGMENT (DS)

INSTRUCTION POINTER (IP)

6 5 4 3 2 1

CONTROL SYSTEM

ARITHMETICLOGIC UNIT

Instruction Queue

OPERANDS

∑ MemoryInterface

InstructionDecoder

Execution Unit

Main components are• Instruction Decoder• Control System• Arithmetic Logic Unit• General Purpose Registers• Flag Register• Pointer & Index registers

Instruction DecoderTranslates instructions fetched from memory

into a series of actions which EU carries out

Control SystemGenerates timing and control signals to

perform the internal operations of the microprocessor

Arithmetic Logic UnitEU has a 16-bit ALU which can ADD,

SUBTRACT, AND, OR, increment, decrement, complement or shift binary numbers

General Purpose Registers EU has 8 general

purpose registers Can be individually

used for storing 8-bit data

AL register is also called Accumulator

Two registers can also be combined to form 16-bit registers

The valid register pairs are – AX, BX, CX, DX

CH CLDH DL

AH AL AX

BH BL BX

CH CL CX

DH DL DX55

Flag Register

8086 has a 16-bit flag registerContains 9 active flagsThere are two types of flags in 8086

• Conditional flags – six flags, set or reset by EU on the basis of results of some arithmetic operations

• Control flags – three flags, used to control certain operations of the processor

U U U U OF DF IF TF SF ZF U AF U PF U CF

Flag Register

1. CF CARRY FLAG Conditional Flags(Compatible with 8085, except OF)

2. PF PARITY FLAG

3. AF AUXILIARY CARRY

4. ZF ZERO FLAG

5. SF SIGN FLAG

6. OF OVERFLOW FLAG

7. TF TRAP FLAG Control Flags8. IF INTERRUPT FLAG

9. DF DIRECTION FLAG57

Flag Register

15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

OF DF IF TF SF ZF AF PF CF

Carry Flag

This flag is set, when there isa carry out of MSB in case ofaddition or a borrow in caseof subtraction.

Parity Flag

This flag is set to 1, if the lowerbyte of the result contains evennumber of 1’s ; for odd numberof 1’s set to zero.

Auxiliary Carry Flag

This is set, if there is a carry from thelowest nibble, i.e, bit three duringaddition, or borrow for the lowestnibble, i.e, bit three, duringsubtraction.

Zero Flag

This flag is set, if the result ofthe computation or comparisonperformed by an instruction iszero

Sign Flag

This flag is set, when the result of any computation

is negative

Tarp FlagIf this flag is set, the processorenters the single step executionmode by generating internalinterrupts after the execution ofeach instruction

Interrupt Flag

Causes the 8086 to recognize external mask interrupts; clearing IF

disables these interrupts.

Direction FlagThis is used by string manipulation instructions. If this flag bitis ‘0’, the string is processed beginning from the lowestaddress to the highest address, i.e., auto incrementing mode.Otherwise, the string is processed from the highest addresstowards the lowest address, i.e., auto incrementing mode.

Over flow FlagThis flag is set, if an overflow occurs, i.e, if the result of a signed

operation is large enough to accommodate in a destination register. The result is of more than 7-bits in size in case of 8-bit signed operation and more than 15-bits in size in case of 16-bit

sign operations, then the overflow will be set.

Registers, Flag

Sl.No. Type Register width Name of register

1 General purpose register

16 bit AX, BX, CX, DX

8 bit AL, AH, BL, BH, CL, CH, DL, DH

2 Pointer register 16 bit SP, BP

3 Index register 16 bit SI, DI

4 Instruction Pointer 16 bit IP

5 Segment register 16 bit CS, DS, SS, ES

6 Flag (PSW) 16 bit Flag register

8086 registers categorized

into 4 groups 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0

OF DF IF TF SF ZF AF PF CF

Register Name of the Register Special Function

AX 16-bit Accumulator Stores the 16-bit results of arithmetic and logic operations

AL 8-bit Accumulator Stores the 8-bit results of arithmetic and logic operations

BX Base register Used to hold base value in base addressing mode to access memory data

CX Count Register Used to hold the count value in SHIFT, ROTATE and LOOP instructions

DX Data Register Used to hold data for multiplication and division operations

SP Stack Pointer Used to hold the offset address of top stack memory

BP Base Pointer Used to hold the base value in base addressing using SS register to access data from stack memory

SI Source Index Used to hold index value of source operand (data) for string instructions

DI Data Index Used to hold the index value of destination operand (data) for string operations

Registers and Special Functions

Bus Interface Unit

Main Components are• Instruction Queue• Segment Registers• Instruction Pointer

Instruction Queue 8086 employs parallel processingWhen EU is busy decoding or executing

current instruction, the buses of 8086 may not be in use.

At that time, BIU can use buses to fetch upto six instruction bytes for the following instructions

BIU stores these pre-fetched bytes in a FIFOregister called Instruction Queue

When EU is ready for its next instruction, it simply reads the instruction from the queue in BIU

Pipelining

EU of 8086 does not have to wait in between for BIU to fetch next instruction byte from memorySo the presence of a queue in 8086

speeds up the processingFetching the next instruction while the

current instruction executes is called pipelining

Memory Segmentation 8086 has a 20-bit address busSo it can address a maximum of 1MB of

memory 8086 can work with only four 64KB segments

at a time within this 1MB rangeThese four memory segments are called

• Code segment• Stack segment• Data segment• Extra segment

Memory

00000H

FFFFFH

1MB Address Range

64KB Memory Segment

Only 4 such segments can be addressed at a time

Code SegmentThat part of memory from where BIU is

currently fetching instruction code bytes

Stack SegmentA section of memory set aside to store

addresses and data while a subprogram executes

Data & Extra SegmentsUsed for storing data values to be used in

the program

Memory

00000H

FFFFFH

1MB Address Range

Code Segment

Stack Segment

Data & Extra Segments

Segment Registers

hold the upper 16-bits of the starting address for each of the segmentsThe four segment registers are

• CS (Code Segment register)• DS (Data Segment register)• SS (Stack Segment register)• ES (Extra Segment register)

Code Segment3

Data SegmentExtra Segment

Stack Segment

Memory00000H

FFFFFH

1MB Address Range

1000 0H

4000 0H5000 0H

F000 0H

Address of a segment is of 20-bitsA segment register stores only upper 16-

bitsBIU always inserts zeros for the lowest 4-

bits of the 20-bit starting address.E.g. if CS = 348AH, then the code

segment will start at 348A0HA 64-KB segment can be located

anywhere in the memory, but will start at an address with zeros in the lowest 4-bits

Instruction Pointer (IP) Register

a 16-bit registerHolds 16-bit offset, of the next instruction

byte in the code segment BIU uses IP and CS registers to generate

the 20-bit address of the instruction to be fetched from memory

Segment3

Code Segment

Extra Segment

Stack Segment

Memory00000H

FFFFFH

1MB Address Range

348A H4214 H

38AB4 H

IPPhysical Address

Start of Code Segment

348A0H

Code Byte MOV AL, BL38AB4H

IP = 4214H

Physical Address Calculation

Stack Segment (SS) Register Stack Pointer (SP) Register

Upper 16-bits of the starting address of stack segment is stored in SS registerIt is located in BIUSP register holds a 16-bit offset from the

start of stack segment to the top of the stackIt is located in EU

Other Pointer & Index Registers

Base Pointer (BP) registerSource Index (SI) registerDestination Index (DI) registerCan be used for temporary storage of dataMain use is to hold a 16-bit offset of a data

word in one of the segments

ADDRESSING MODES OF

808675

Various Addressing Modes1. Immediate Addressing Mode2. Register Addressing Mode3. Direct Addressing Mode4. Register Indirect Addressing Mode5. Index Addressing Mode6. Based Addressing Mode7. Based & Indexed Addressing Mode8. Based & Indexed with displacement Addressing

Mode9. Strings Addressing Mode

76Presented by C.GOKUL,AP/EEE , Velalar College of Engg & Tech, Erode

1. IMMEDIATE ADDRESSING MODE• The instruction will specify the name

of the register which holds the data to be operated by the instruction.

• Source data is within the instruction

• Ex: MOV AX,10ABH

AL=ABH, AH=10H

2.REGISTER ADDRESSING MODE

• In immediate addressing mode, an 8-bit or 16-bit data is specified as part of the instruction

• Ex: MOV AX,BLH

MOV AX,BLH

3. DIRECT ADDRESSING MODE

• Memory address is supplied with in the instruction

• Mnemonic: MOV AH,[MEMBDS]AH [1000H]

• But the memory address is notindex or pointer register

4. REGISTER INDIRECT ADDRESSING MODE

• Memory address is supplied in an index or pointer register

• EX:

MOV AX,[SI] ; AL [SI] ; AH [SI+1]JMP [DI] ; IP [DI+1: DI]INC BYTE PTR [BP] ; [BP] [BP]+1DEC WORD PTR [BX] ;

[BX+1:BX] [BX+1:BX]-1

5.Indexed Addressing Mode

• Memory address is the sum of index register plus displacement

MOV AX,[SI+2] AL [SI+2]; AH [SI+3]JMP [DI+2] IP [BX+3:BX+2]

6. Based Addressing Mode

• Memory address is the sum of the BX or BP base register plus a displacement within instruction

• Ex: MOV AX,[BP+2] AL [BP+2]; AH [BP+3]JMP [BX+2] IP [BX+3:BX+2]

7.BASED & INDEX ADDRESSING MODES

• Memory address is the sum of the index register & base register

Ex:MOV AX,[BX+SI] ; AL [BX+SI] ; AH [BX+SI+1]JMP [BX+DI] ; IP [BX+DI+1 : BX+DI]INC BYTE PTR [BP+SI] ; [BP] [BP]+1DEC WORD PTR [BP+DI] ;

[BX+1:BX] [BX+1:BX]-1

8. BASED & INDEXED WITH DISPLACEMENT ADDRESSING MODE

• Memory address is the sum of an index register , base register and displacement within instruction

MOV AX,[BX+SI+6] ; AL [BX+SI+6] ; AH [BX+SI+7]JMP [BX+DI+6] ; IP [BX+DI+7 : BX+DI+6]INC BYTE PTR [BP+SI+5] ; DEC WORD PTR [BP+DI+5] ;

9. Strings Addressing Mode

• The memory source address is a register SI in the data segment, and the memory destination address is register DI in the extra segment

• Ex: MOVSB [ES:DI] [DS:SI]

• If DF=0 SI SI+1 , DI DI+1DF=1 SI SI-1 , DI DI-1

INSTRUCTION SET of 8086

• Instruction:- An instruction is a binary pattern designed inside a microprocessor to perform a specific function.

• Opcode:- It stands for operational code. It specifies the type of operation to be performed by CPU. It is the first field in the machine language instruction format.

• E.g. 08 is the opcode for instruction “MOV X,Y”.

• Operand:- We can also say it as data on which operation should act. operands may be register values or memory values. The CPU executes the instructions using information present in this field. It may be 8-bit data or 16-bit data.

Instruction set basics

• Assembler:- it converts the instruction into sequence of binary bits, so that this bits can be read by the processor.

• Mnemonics:- these are the symbolic codes for either instructions or commands to perform a particular function.

• E.g. MOV, ADD, SUB etc.

Instruction set basics

Types of instruction set of 8086 microprocessor

(1). Data Copy/Transfer instructions.

(2). Arithmetic & Logical instructions.

(3). Branch instructions.

(4). Loop instructions.

(5). Machine Control instructions.

(6). Flag Manipulation instructions.

(7). Shift & Rotate instructions.

(8). String instructions.89

(1). Data copy/transfer instructions.(1). MOV Destination, Source

There will be transfer of data from source to destination. Source can be register, memory location or immediate

data. Destination can be register or memory operand. Both Source and Destination cannot be memory location

or segment registers at the same time. E.g. (1). MOV CX, 037A H; (2). MOV AL, BL; (3). MOV BX, [0301 H];

BX 2000HAX 2000H

BEFORE EXECUTION

AFTER EXECUTION

MOV BX,AX

MOV CL,M

BEFORE EXECUTION

AFTER EXECUTION

Stack Pointer It is a 16-bit register, contains the address of the data

item currently on top of the stack.

Stack operation includes pushing (providing) data on to the stack and popping (taking)data from the stack.

Pushing operation decrements stack pointer and Popping operation increments stack pointer. i.e. there is a last in first out (LIFO) operation.

(2). Push Source Source can be register, segment register or

memory. This instruction pushes the contents of specified

source on to the stack. In this stack pointer is decremented by 2. The higher byte data is pushed first (SP-1). Then lower byte data is pushed (SP-2).

E.g.: (1). PUSH AX; (2). PUSH DS; (3). PUSH [5000H];

INITIAL POSITION

DECREMENTS SP & STORES HIGHER BYTE

HIGHER BYTE

DECREMENTS SP & STORES LOWER BYTE

LOWER BYTE

HIGHER BYTE

(1) STACK POINTER

(2) STACK POINTER

(3) STACK POINTER

CH 10 CL 50

SP 2002H

SP 2000H

BEFORE EXECUTION

AFTER EXECUTION

PUSH CX

(3) POP Destination Destination can be register, segment register or

memory. This instruction pops (takes) the contents of

specified destination. In this stack pointer is incremented by 2. The lower byte data is popped first (SP+1). Then higher byte data is popped (SP+2).

E.g. (1). POP AX; (2). POP DS; (3). POP [5000H];

INITIAL POSITION AND READS LOWER BYTE

LOWER BYTE

INCREMENTS SP & READS HIGHER BYTE

LOWER BYTE

HIGHER BYTE

INCREMENTS SP

LOWER BYTE

HIGHER BYTE

(1) STACK POINTER

(2) STACK POINTER

(3) STACK POINTER

SP 2000H

SP 2002H

BEFORE EXECUTION

AFTER EXECUTION

POP BX

2000H2001H

(4). XCHG Destination, source;

• This instruction exchanges contents of Source with destination.

• It cannot exchange two memory locations directly.

•The contents of AL are exchanged with BL.

•The contents of AH are exchanged with BH.

•E.g.(1). XCHG BX, AX;(2). XCHG [5000H],AX;

AH 20 AL 40

BH 70 BL 80

AH 70 AL 80

BH 20 BL 40

BEFORE EXECUTION AFTER EXECUTION

XCHG AX,BX100

(5)IN AL/AX, 8-bit/16-bit port address

It reads from the specified port address. It copies data to accumulator from a port with 8-

bit or 16-bit address. DX is the only register is allowed to carry port

address. E.g.(1). IN AL, 80H;(2). IN AX,DX; //DX contains address of 16-bit

port.101

10 AL 10

BEFORE EXECUTION

AFTER EXECUTION

IN AL,80H

PORT 80H

OUT 8-bit/16-bit port address, AL/AX

It writes to the specified port address. It copies contents of accumulator to the port

with 8-bit or 16-bit address. DX is the only register is allowed to carry port

address. E.g.(1). OUT 80H,AL;(2). OUT DX,AX; //DX contains address of 16-bit

port.103

10 AL 40

40 AL 40

BEFORE EXECUTION

AFTER EXECUTION

OUT 50H,AL

PORT 50H

(7) XLAT

Also known as translate instruction. It is used to find out codes in case of code conversion. i.e. it translates code of the key pressed to the

corresponding 7-segment code. After execution this instruction contents of AL register

always gets replaced. E.g. XLAT;

8.LEA 16-bit register (source), address (dest.)

LEA Also known as Load Effective Address (LEA).

It loads effective address formed by the destination into the source register.

E.g.(1). LEA BX,Address;(2). LEA SI,Address[BX];

(9). LDS 16-bit register (source), address (dest.);(10). LES 16-bit register (source), address (dest.);

LDS Also known as Load Data Segment (LDS). LES Also known as Load Extra Segment (LES). It loads the contents of DS (Data Segment) or ES

(Extra Segment) & contents of the destination to the contents of source register.

E.g.(1). LDS BX,5000H;(2). LES BX,5000H;

(1). LDS BX,5000H;(2). LES BX,5000H;

(11). LAHF:- This instruction loads the AH register from the contents of lower byte of the flag register.

This command is used to observe the status of the all conditional flags of flag register.

E.g. LAHF;

(12). SAHF:- This instruction sets or resets all conditional flags of flag register with respect to the corresponding bit positions.

If bit position in AH is 1 then related flag is set otherwise flag will be reset.

E.g. SAHF;

PUSH & POP

(13). PUSH F:- This instruction decrements the stack pointer by 2.

It copies contents of flag register to the memory location pointed by stack pointer.

E.g. PUSH F;

(14). POP F:- This instruction increments the stack pointer by 2.

It copies contents of memory location pointed by stack pointer to the flag register.

E.g. POP F;110

(2). Arithmetic Instructions

These instructions perform the operations like:

Addition, Subtraction, Increment, Decrement.

(2). Arithmetic Instructions(1). ADD destination, source;

This instruction adds the contents of source operand with the contents of destination operand.

The source may be immediate data, memory location or register.

The destination may be memory location or register. The result is stored in destination operand. AX is the default destination register.

E.g. (1). ADD AX,2020H;(2). ADD AX,BX;

AH 10 AL 10

AFTER EXECUTIONBEFORE EXECUTION

AH 10 AL 10

BH 20 BL 20

ADD AX,2020H

ADD AX,BX

AH 30 AL 30

1010+20203030

AH 30 AL 30

BH 20 BL 20

ADC destination, source This instruction adds the contents of source

operand with the contents of destination operand with carry flag bit.

The destination may be memory location or register.

The result is stored in destination operand. AX is the default destination register.

E.g. (1). ADC AX,2020H;(2). ADC AX,BX;

(3) INC source This instruction increases the contents of source

operand by 1. The source may be memory location or register. The source can not be immediate data. The result is stored in the same place.

E.g. (1). INC AX;(2). INC [5000H];

AFTER EXECUTION

INC [5000H]

BEFORE EXECUTION

INC AXAH 10 AL 11 AH 10 AL 12

1011 5000H 1012

4. DEC source This instruction decreases the contents of

source operand by 1. The source may be memory location or register. The source can not be immediate data. The result is stored in the same place.

E.g. (1). DEC AX;(2). DEC [5000H];

AFTER EXECUTION

DEC [5000H]

BEFORE EXECUTION

DEC AXAH 10 AL 11 AH 10 AL 10

1051 5000H 1050

(5) SUB destination, source; This instruction subtracts the contents of source

operand from contents of destination. The source may be immediate data, memory

location or register. The destination may be memory location or

register. The result is stored in the destination place.

E.g. (1). SUB AX,1000H;(2). SUB AX,BX;

SUB AX,1000H

SUB AX,BX

AH 20 AL 00 AH 10 AL 00

2000-1000=1000

AH 20 AL 00BH 10 BL 00

AH 10 AL 00

BH 10 BL 00

(6). SBB destination, source; Also known as Subtract with Borrow. This instruction subtracts the contents of source

operand & borrow from contents of destination operand.

The destination may be memory location or register.

The result is stored in the destination place.

E.g. (1). SBB AX,1000H;(2). SBB AX,BX;

AH 20 AL 20

BH 10 BL 10

SBB AX,1000H

SBB AX,BX

AH 10 AL 192020

- 10001020-

1=1019

AH 10 AL 19

BH 10 BL 10

(7). CMP destination, source Also known as Compare. This instruction compares the contents of source

operand with the contents of destination operands. The source may be immediate data, memory

location or register. The destination may be memory location or

register. Then resulting carry & zero flag will be set or reset.

E.g. (1). CMP AX,1000H;(2). CMP AX,BX;

AFTER EXECUTION

CMP AX,BX

BEFORE EXECUTION

CY 0 Z 1

D=S: CY=0,Z=1D>S: CY=0,Z=0D<S: CY=1,Z=0

AH 10 AL 00BH 10 BL 00

CMP AX,BX CY 0 Z 0AH 10 AL 00BH 00 BL 10

CMP AX,BX CY 1 Z 0AH 10 AL 00BH 20 BL 00

AAA (ASCII Adjust after Addition): The data entered from the terminal is in ASCII format.

In ASCII, 0 – 9 are represented by 30H – 39H.

This instruction allows us to add the ASCII codes.

This instruction does not have any operand.

Other ASCII Instructions: AAS (ASCII Adjust after Subtraction)

AAM (ASCII Adjust after Multiplication)

AAD (ASCII Adjust Before Division)

DAA (Decimal Adjust after Addition)

It is used to make sure that the result of adding two BCD numbers is adjusted to be a correct BCD number.

It only works on AL register.

DAS (Decimal Adjust after Subtraction)

It is used to make sure that the result of subtracting two BCD numbers is adjusted to be a correct BCD number.

It only works on AL register.

MUL operand Unsigned Multiplication. Operand contents are positively signed. Operand may be general purpose register or memory

location. If operand is of 8-bit then multiply it with contents of AL. If operand is of 16-bit then multiply it with contents of AX. Result is stored in accumulator (AX).

E.g. (1). MUL BH // AX= AL*BH; // (+3) * (+4) = +12.

(2). MUL CX // AX=AX*CX;

IMUL operand Signed Multiplication. Operand contents are negatively signed. Operand may be general purpose register, memory location

or index register. If operand is of 8-bit then multiply it with contents of AL. If operand is of 16-bit then multiply it with contents of AX. Result is stored in accumulator (AX).

E.g. (1). IMUL BH // AX= AL*BH; // (-3) * (-4) = 12.

(2). IMUL CX // AX=AX*CX;

DIV operand Unsigned Division. Operand may be register or memory. Operand contents are positively signed. Operand may be general purpose register or

memory location. AL=AX/Operand (8-bit/16-bit) & AH=Remainder.

E.g. MOV AX, 0203 // AX=0203 MOV BL, 04 // BL=04 IDIV BL // AL=0203/04=50 (i.e. AL=50 & AH=03)

IDIV operand Signed Division. Operand may be register or memory. Operand contents are negatively signed. Operand may be general purpose register or

memory location. AL=AX/Operand (8-bit/16-bit) & AH=Remainder.

E.g. MOV AX, -0203 // AX=-0203 MOV BL, 04 // BL=04 DIV BL // AL=-0203/04=-50 (i.e. AL=-50 &

AH=03)

Multiplication and Division Examples

AH 00 AL 05

BH 00 BL 03CH CL

BEFORE EXECUTION

AFTER EXECUTION

MUL BX AX=lower 16 bit {000F}DX=Higher 16 bit {0000}

AH 00 AL 0F

BH BLCH CLDH 00 DL 00

0005*0003 = 0000 000F

AH 00 AL 0F

BH 00 BL 02

BEFORE EXECUTION

AFTER EXECUTION

DIV BX

AH 00 AL 07

BH BLCH CLDH 00 DL 01

AX=Quotient {0007}DX=Reminder {0001}

000F = 7 1

0002 2

LOGICAL (or) Bit Manipulation Instructions

These instructions are used at the bit level.

These instructions can be used for:

Testing a zero bit

Set or reset a bit

Shift bits across registers

Bit Manipulation Instructions(LOGICAL Instructions)

• AND– Especially used in clearing certain bits (masking)

xxxx xxxx AND 0000 1111 = 0000 xxxx (clear the first four bits)

– Examples: AND BL, 0FH

• OR– Used in setting certain bits

xxxx xxxx OR 0000 1111 = xxxx 1111(Set the upper four bits)

XOR– Used in Inverting bits

xxxx xxxx XOR 0000 1111 = xxxxx’x’x’x’

-Example: Clear bits 0 and 1, set bits 6 and 7, invertbit 5 of register CL:

AND CL, FCH ; 1111 1100B

OR CL, C0H ; 1100 0000B

XOR CL, 20H ; 0010 0000B

AND AX,BXH

AH 11 AL 11

BH 11 BL 11

AH FF AL FF

BH 11 BL 11

AX = FFFFH = 1111 1111 1111 1111BX = 1111H = 0001 0001 0001 0001 AND (&)

AND 0001 0001 0001 0001 = 1111H

OR AX,BXH

AH FF AL FF

BH 11 BL 11

AH FF AL FF

BH 11 BL 11

AX = FFFFH = 1111 1111 1111 1111BX = 1111H = 0001 0001 0001 0001 OR

OR 1111 1111 1111 1111 = FFFFH

XOR AX,BXH

AH EE AL EE

BH 11 BL 11

AH FF AL FF

BH 11 BL 11

AX = FFFFH = 1111 1111 1111 1111BX = 1111H = 0001 0001 0001 0001

XOR 1110 1110 1110 1110 = EEEEH

NOT AXH

AH 00 AL 00AH FF AL FF

AX = FFFFH = 1111 1111 1111 1111

NOT 0000 0000 0000 0000 = 0000H

SHL Instruction

The SHL (shift left) instruction performs a logical left shift on the destination operand, filling the lowest bit with 0.

mov dl,5d

shl dl,1

SHR Instruction

The SHR (shift right) instruction performs a logical right shift on the destination operand. The highest bit position is filled with a zero.

MOV DL,80dSHR DL,1 ; DL = 40SHR DL,2 ; DL = 10

SAR Instruction

SAR (shift arithmetic right) performs a right arithmetic shift on the destination operand.

An arithmetic shift preserves the number's sign.

MOV DL,-80SAR DL,1 ; DL = -40SAR DL,2 ; DL = -10

mov dl,5

shl dl,1

Shifting left n bits multiplies the operand by 2n

For example, 5 * 22 = 20

Shifting right n bits divides the operand by 2n

For example, 80 / 23 = 10

0 0 0 0 1 0 1 0

0 0 0 0 0 1 0 1 = 5

Before:

After:

ROL Instruction

ROL (rotate) shifts each bit to the left The highest bit is copied into both the Carry flag

and into the lowest bit No bits are lost

MOV Al,11110000bROL Al,1 ; AL = 11100001b

MOV Dl,3FhROL Dl,4 ; DL = F3h

ROR Instruction ROR (rotate right) shifts each bit to the right The lowest bit is copied into both the Carry flag and

into the highest bit No bits are lost

MOV AL,11110000bROR AL,1 ; AL = 01111000b

MOV DL,3FhROR DL,4 ; DL = F3h

RCL Instruction RCL (rotate carry left) shifts each bit to the left Copies the Carry flag to the least significant bit Copies the most significant bit to the Carry flag

CLC ; CF = 0MOV BL,88H ; CF,BL = 0 10001000bRCL BL,1 ; CF,BL = 1 00010000bRCL BL,1 ; CF,BL = 0 00100001b

RCR Instruction RCR (rotate carry right) shifts each bit to the right Copies the Carry flag to the most significant bit Copies the least significant bit to the Carry flag

STC ; CF = 1MOV AH,10H ; CF,AH = 00010000 1RCR AH,1 ; CF,AH = 10001000 0

SHL Instruction

The SHL (shift left) instruction performs a logical left shift on the destination operand, filling the lowest bit with 0.

0 0 0 0 0 1 0 1 =05H

0 0 0 0 1 0 1 0CF

BEFORE EXECUTION

AFTER EXECUTION

SHR Instruction

0 0 0 0 0 1 0 1 =05H

0 0 0 0 0 0 1 0CF

BEFORE EXECUTION

AFTEREXECUTION

ROL Instruction

0 0 0 0 0 1 0 1 =05H

0 0 0 0 1 0 1 0CF

0 =0AH

BEFORE EXECUTION

AFTER EXECUTION

ROR Instruction

0 0 0 0 0 1 0 1 =05H

1 0 0 0 0 0 1 0CF

1 =82H

BEFORE EXECUTION

AFTER EXECUTION

Branching Instructions (or)Program Execution Transfer

Instructions

These instructions cause change in the sequence of the execution of instruction.

This change can be through a condition or sometimes unconditional.

The conditions are represented by flags.

CALL Des:

This instruction is used to call a subroutine or function or procedure.

The address of next instruction after CALL is saved onto stack.

It returns the control from procedure to calling program.

Every CALL instruction should have a RET.

SUBROUTINE & SUBROUTINE HANDILING INSTRUCTIONS

Call subroutine A

Next instruction

Call subroutine A

Next instruction

Main program

Subroutine A

First Instruction

Return

JMP Des:

This instruction is used for unconditional jump from one place to another.

Jxx Des (Conditional Jump):

All the conditional jumps follow some conditional statements or any instruction that affects the flag.

Conditional Jump TableMnemonic Meaning

JA Jump if Above

JAE Jump if Above or Equal

JB Jump if Below

JBE Jump if Below or Equal

JC Jump if Carry

JE Jump if Equal

JNC Jump if Not Carry

JNE Jump if Not Equal

JNZ Jump if Not Zero

JPE Jump if Parity Even

JPO Jump if Parity Odd

JZ Jump if Zero160

Loop Des:

This is a looping instruction.

The number of times looping is required is placed in the CX register.

With each iteration, the contents of CX are decremented.

ZF is checked whether to loop again or not.

String Instructions String in assembly language is just a sequentially stored bytes or

words.

There are very strong set of string instructions in 8086.

By using these string instructions, the size of the program is considerably reduced.

CMPS Des, Src:

It compares the string bytes or words.

SCAS String:

It scans a string.

It compares the String with byte in AL or with word in AX.

MOVS / MOVSB / MOVSW:

It causes moving of byte or word from one string to another.

In this instruction, the source string is in Data Segment and destination string is in Extra Segment.

SI and DI store the offset values for source and destination index.

1. Copying a string (MOV SB)MOV CX,0003 copy 3 memory locationsMOV SI,1000MOV DI,2000

L1 CLDMOV SBDEC CX decrement CXJNZ L1HLT

2. Find & Replace

REP (Repeat):

This is an instruction prefix.

It causes the repetition of the instruction until CX becomes zero.

E.g.: REP MOVSB STR1, STR2

It copies byte by byte contents.

REP repeats the operation MOVSB until CX becomes zero.

Processor Control Instructions These instructions control the processor itself.

8086 allows to control certain control flags that:

causes the processing in a certain direction

processor synchronization if more than one microprocessor attached.

It sets the carry flag to 1.

It clears the carry flag to 0.

It complements the carry flag.

STD: It sets the direction flag to 1.

If it is set, string bytes are accessed from higher memory address to lower memory address.

CLD: It clears the direction flag to 0.

If it is reset, the string bytes are accessed from lower memory address to higher memory address.

HLT instruction – HALT processing

The HLT instruction will cause the 8086 to stop fetching andexecuting instructions.

NOP instructionthis instruction simply takes up three clock cycles and does no

processing.

LOCK instructionthis is a prefix to an instruction. This prefix makes sure that during

execution of the instruction, control of system bus is not taken by othermicroprocessor.

WAIT instructionthis instruction takes 8086 to an idle condition. The CPU

will not do any processing during this.171

INSTRUCTION SET-summary1.DATA TRANSFER INSTRUCTIONS

Mnemonic Meaning Format Operation

MOV Move Mov D,S (S) (D)

XCHG Exchange XCHG D,S (S) (D)

LEA Load Effective Address LEA Reg16,EA EA (Reg16)

PUSH pushes the operand into top of stack.

PUSH BX sp=sp-2Copy 16 bit value to top

of stack

POP pops the operand from top of stack to Des.

POP BX Copy top of stack to 16 bit reg

sp=sp+2

IN transfers the operand from specified port to accumulator register.

IN AL,28

OUT transfers the operand from accumulator to specified port.

OUT 28,AL

2. ARITHMETIC INSTRUCTIONSMnemonic Meaning Format Operation

SUB Subtract SUB D,S (D) - (S) (D)

Borrow (CF)

SBB Subtract with borrow

SBB D,S (D) - (S) - (CF) (D)

DEC Decrement by one DEC D (D) - 1 (D)

NEG Negate NEG D

DAS Decimal adjust for subtraction

DAS Convert the result in AL to packed decimal format

AAS ASCII adjust for subtraction

AAS (AL) difference (AH) dec by 1 if borrow

ADD Addition ADD D,S (S)+(D) (D) carry (CF)

ADC Add with carry ADC D,S (S)+(D)+(CF) (D) carry (CF)

INC Increment by one INC D (D)+1 (D)

AAA ASCII adjust for addition

AAA If the sum is >9, AH

is incremented by 1DAA Decimal adjust for

addition DAA Adjust AL for decimal Packed BCD173

Mnemonic Meaning Format Operation

Logical AND

Logical Inclusive OR

Logical Exclusive OR

LOGICAL NOT

AND D,S

OR D,S

XOR D,S

(S) · (D) → (D)

(S)+(D) → (D)

(S) (D)→(D)

(D) → (D)

3. Bit Manipulation Instructions(Logical Instructions)

Shift & Rotate Instructions

Mnemonic Meaning Format

ROL Rotate Left ROL D,Count

ROR Rotate Right ROR D,Count

RCL Rotate Left through Carry RCL D,Count

RCR Rotate right through Carry RCR D,Count

Mnemonic Meaning FormatSAL/SHL

Shift arithmetic Left/Shift Logical left

Shift logical right

Shift arithmeticright

SAL/SHL D, Count

SHR D, Count

SAR D, Count

4. Branching or PROGRAM EXECUTION TRANSFER INSTRUCTIONS• CALL - call a subroutine• RET - returns the control from procedure to calling

program

• JMP Des – Unconditional Jump• Jxx Des – conditional Jump (ex: JC 8000)• Loop Des

5. STRING INSTRUCTIONS

• CMPS Des, Src - compares the string bytes• SCAS String - scans a string• MOVS / MOVSB / MOVSW - moving of byte or

word• REP (Repeat) - repetition of the instruction

6. PROCESSOR CONTROL INSTRUCTIONS• STC – set the carry flag (CF=1)• CLC – clear the carry flag (CF=0)• STD – set the direction flag (DF=1)• CLD – clear the direction flag (DF=0)• HLT – stop fetching & execution• NOP – no operation(no processing)• LOCK - control of system bus is not taken by other µP

• WAIT - CPU will not do any processing• ESC - µP does NOP or access a data from memory for coprocessor

Assembler Directives

ASSUME,END,ENDP,EQU,EVEN,DD – 8 mark

Directives Expansion

• ASSUME Directive - The ASSUME directive is used to tell the assembler that the name of the logical segment should be used for a specified segment.

• DB(define byte) - DB directive is used to declare a byte type variable or to store a byte in memory location.

• DW(define word) - The DW directive is used to define a variable of type word or to reserve storage location of type word in memory.

• DD(define double word) :This directive is used to declare a variable of type double word or restore memory locations which can be accessed as type double word.

• DQ (define quadword) :This directive is used to tell the assembler to declare a variable 4 words in length or to reserve 4 words of storage in memory .

• DT (define ten bytes):It is used to inform the assembler to define a variable which is 10bytes in length or to reserve 10 bytes of storage in memory.

• END- End program .This directive indicates the assembler that this is the end of the program module. The assembler ignores any statements after an END directive.

• ENDP- End procedure: It indicates the end of the procedure (subroutine) to the assembler.

• ENDS-End Segment: This directive is used with the name of the segment to indicate the end of that logical segment.

• EQU - This EQU directive is used to give a name to some value or to a symbol.

• PROC - The PROC directive is used to identify the start of a procedure.

• PTR -This PTR operator is used to assign a specific type of a variable or to a label.

• ORG -Originate : The ORG statement changes the starting offset address of the data.

Directives examples

• ASSUME CS:CODE cs=> code segment• ORG 3000• NAME DB ‘THOMAS’• POINTER DD 12341234H

• FACTOR EQU 03H

Assembly Language Programming(ALP)

Program 1: Increment an 8-bit number

• MOV AL, 05H Move 8-bit data to AL.• INC AL Increment AL.

Program 2: Increment an 16-bit number

• MOV AX, 0005H Move 16-bit data to AX.• INC AX Increment AX.

After Execution AL = 06H

After Execution AX = 0006H

Program 3: Decrement an 8-bit number

• MOV AL, 05H Move 8-bit data to AL.• DEC AL Decrement AL.

Program 4: Decrement an 16-bit number

• MOV AX, 0005H Move 16-bit data to AX.• DEC AX Decrement AX.

Program 5: 1’s complement of an 8-bit number.

• MOV AL, 05H Move 8-bit data to AL.• NOT AL Complement AL.

Program 6: 1’s complement of a 16-bit number.

• MOV AX, 0005H Move 16-bit data to AX.• NOT AX Complement AX.

After Execution AL = FAH

After Execution AX = FFFAH

Program 7: 2’s complement of an 8-bit number.• MOV AL, 05H Move 8-bit data to AL.• NOT AL Complement AL.• INC AL Increment AL

Program 8: 2’s complement of a 16-bit number.

• MOV AX, 0005H Move 16-bit data to AX.• NOT AX Complement AX.• INC AX Increment AX

After Execution AX = FAH + 1 = FB

After Execution AX = FFFAH + 1 = FFFB

Program 9: Add two 8-bit numbers

MOV AL, 05H Move 1st 8-bit number to AL.MOV BL, 03H Move 2nd 8-bit number to BL.ADD AL, BL Add BL with AL.

Program 10: Add two 16-bit numbers

MOV AX, 0005H Move 1st 16-bit number to AX.MOV BX, 0003H Move 2nd 16-bit number to BX.ADD AX, BX Add BX with AX.

Program 11: subtract two 8-bit numbers

MOV AL, 05H Move 1st 8-bit number to AL.MOV BL, 03H Move 2nd 8-bit number to BL.SUB AL, BL subtract BL from AL.

Program 12: subtract two 16-bit numbers

MOV AX, 0005H Move 1st 16-bit number to AX.MOV BX, 0003H Move 2nd 16-bit number to BX.SUB AX, BX subtract BX from AX.

Program 13: Multiply two 8-bit unsigned numbers.

MOV AL, 04H Move 1st 8-bit number to AL.MOV BL, 02H Move 2nd 8-bit number to BL.MUL BL Multiply BL with AL and the result will

be in AX.

Program 14: Multiply two 8-bit signed numbers.

MOV AL, 04H Move 1st 8-bit number to AL.MOV BL, 02H Move 2nd 8-bit number to BL.IMUL BL Multiply BL with AL and the result will

be in AX.

Program 15: Multiply two 16-bit unsigned numbers.

MOV AX, 0004H Move 1st 16-bit number to AL.MOV BX, 0002H Move 2nd 16-bit number to BL.MUL BX Multiply BX with AX and the result will

be in DX:AX {4*2=0008=> 08=> AX , 00=> DX}

Program 16: Divide two 16-bit unsigned numbers.

MOV AX, 0004H Move 1st 16-bit number to AL.MOV BX, 0002H Move 2nd 16-bit number to BL.DIV BX Divide BX from AX and the result will be in AX & DX

{4/2=0002=> 02=> AX ,00=>DX} (ie: Quotient => AX , Reminder => DX )

Detailed coding16 BIT ADDITION

Detailed coding16 BIT SUBTRACTION

16 BIT MULTIPLICATION

16 BIT DIVISION

SUM of N numbersMOV AX,0000MOV SI,1100MOV DI,1200MOV CX,0005 5 NUMBERS TO BE TAKEN SUMMOV DX,0000

L1: ADD AX,[SI]INC SIINC DXCMP CX,DXJNZ L1MOV [1200],AXHLT 199

Average of N numbersMOV AX,0000MOV SI,1100MOV DI,1200MOV CX,0005 5 NUMBERS TO BE TAKEN AVERAGEMOV DX,0000

L1: ADD AX,[SI]INC SIINC DXCMP CX,DXJNZ L1DIV CX AX=AX/5(AVERAGE OF 5 NUMBERS)MOV [1200],AXHLT 200Presented by C.GOKUL,AP/EEE , Velalar College of Engg & Tech, Erode

FACTORIAL of NMOV CX,0005 5 Factorial=5*4*3*2*1=120MOV DX,0000MOV AX,0001

L1: MUL CXDEC DXCMP CX,DXJNZ L1MOV [1200],AXHLT

ASCENDING ORDER

DECENDING ORDER

Note: change the coding JNB L1 into JB L1 in the LINE 10204

LARGEST, smallest NUMBER IN AN ARRAY

LARGEST NUMBER

SMALLEST NUMBER

Modular Programming

• Generally , industry-programming projects consist of thousands of lines of instructions or operation code.

• The size of the modules are reduced to a humanly comprehensible and manageable level.

• Program is composed from several smaller modules. Modules could be developed by separate teams concurrently.OBJ modules (Object modules).

• The .OBJ modules so produced are combined using a LINK program.

• Modular programming techniques simplify the software development process

CHARACTERISTICS of module:1. Each module is independent of other modules.2. Each module has one input and one output.3. A module is small in size.4. Programming a single function per module is a goalAdvantages of Modular Programming:• It is easy to write, test and debug a module.• Code can be reused.• The programmer can divide tasks.• Re-usable Modules can be re-used within a programDRAWBACKS:Modular programming requires extra time and memory

MODULAR PROGRAMMING:1.LINKING & RELOCATION2.STACKS3.Procedures4.Interrupts & Interrupt Routines5.Macros

LINKING & RELOCATION

LINKER• A linker is a program used to join together several

object files into one large object file. • The linker produces a link file which contains the

binary codes for all the combined modules.

The linker program is invoked using the following options. C> LINK

or C>LINK MS.OBJ

• The loader is a part of the operating system and places codes into the memory after reading the ‘.exe’ file

• A program called locator reallocates the linked file and creates a file for permanent location of codes in a standard format.

Creation and execution of a program

Loader->Loader is a utility program which takes object code as

input prepares it for execution and loads the executable code into the memory .

->Loader is actually responsible for initializing the process of execution.

Functions of loaders:1.It allocates the space for program in the memory(Allocation)2.It resolves the code between the object modules(Linking)3. some address dependent locations in the program, address constants

must be adjusted according to allocated space(Relocation)4. It also places all the machine instructions and data of corresponding

programs and subroutines into the memory .(Loading)

Relocating loader (BSS Loader)• When a single subroutine is changed then all

the subroutine needs to be reassembled.• The binary symbolic subroutine (BSS) loader

used in IBM 7094 machine is relocating loader.• In BSS loader there are many procedure

segments• The assembler reads one sourced program

and assembles each procedure segment independently

• The output of the relocating loader is the object program• The assembler takes the source program as input; this source

program may call some external routines.SEGMENT COMBINATION:

ASM-86 assembler regulating the way segments with the same name are concatenated & sometimes they are overlaid.

Form of segment directive:Segment name SEGEMENT Combine-type

Possible combine-type are:• PUBLIC• COMMON• STACK• AT• MEMORY

Procedures219

CALL & RET instruction

• Procedure is a part of code that can be called from your program in order to make some specific task. Procedures make program more structural and easier to understand.

• syntax for procedure declaration:name PROC

…………. ; here goes the code…………. ; of the procedure ...

name ENDP

here PROC is the procedure name.(used in top & bottom)RET - used to return from OS. CALL-call a procedure PROC & ENDP – complier directivesCALL & RET - instructions 220

EXAMPLE 1 (call a procedure)ORG 100hCALL m1MOV AX, 2RET ; return to operating system.

m1 PROCMOV BX, 5RET ; return to caller.m1 ENDPEND

• The above example calls procedure m1, does MOV BX, 5 & returns to the next instruction after CALL: MOV AX, 2.

Example 2 : several ways to pass parameters to procedure

ORG 100hMOV AL, 1MOV BL, 2CALL m2CALL m2CALL m2CALL m2

RET ; return to operating system.

m2 PROCMUL BL ; AX = AL * BL.RET ; return to caller.m2 ENDPEND

value of AL register is update every time theprocedure is called.final result in AX register is 16 (or 10h)

PUSH & POP instruction

• Stack is an area of memory for keeping temporary data.

• STACK is used by CALL & RET instructions.PUSH -stores 16 bit value in the stack.POP -gets 16 bit value from the stack.

• PUSH and POP instruction are especially useful because we don't have too much registers to operate

1. Store original value of the register in stack (using PUSH).

2. Use the register for any purpose.3. Restore the original value of the register from stack

(using POP).

Example-1 (store value in STACK using PUSH & POP)

ORG 100hMOV AX, 1234hPUSH AX ; store value of AX in stack.MOV AX, 5678h ; modify the AX value.POP AX ; restore the original value of AX.RETEND

Example 2: use of the stack is for exchanging the values

ORG 100hMOV AX, 1212h ; store 1212h in AX.MOV BX, 3434h ; store 3434h in BXPUSH AX ; store value of AX in stack.PUSH BX ; store value of BX in stack.POP AX ; set AX to original value of BX.POP BX ; set BX to original value of AX.RETEND

push 1212h and then 3434h, on pop we will first get 3434h and only after it 1212h 226

MACROS227

How to pass parameters using macros-6/8 Mark

• Macros are just like procedures, but not really.• Macros exist only until your code is compiled• After compilation all macros are replaced with

real instructions• several macros to make coding easier(Reduce

large & complex programs)Example (Macro definition)

name MACRO [parameters,...]<instructions>ENDM

Example1 : Macro DefinitionsSAVE MACRO definition of MACRO name SAVE

PUSH AXPUSH BXPUSH CXENDM

RETREIVE MACRO Another definition of MACRO name RETREIVE

POP CXPOP BXPOP AXENDM

MACROS with Parameters

Example:COPY MACRO x, y ; macro named COPY with

2 parameters{x, y}

PUSH AXMOV AX, xMOV y, AXPOP AXENDM

INTERRUPTS &

INTERRUPT SERVICE ROUTINE(ISR)

INTERRUPT & ISR ?

• ‘Interrupts’ is to break the sequence of operation.

• While the CPU is executing a program, on ‘interrupt’ breaks the normal sequence of execution of instructions, diverts its execution to some other program called Interrupt Service Routine (ISR)

• Maskable Interrupt: An Interrupt that can be disabled or ignored by the instructions of CPU are called as Maskable Interrupt.

• Non- Maskable Interrupt: An interrupt that cannot be disabled or ignored by the instructions of CPU are called as Non- Maskable Interrupt.

• Software interrupts are machine instructions that amount to a call to the designated interrupt subroutine, usually identified by interrupt number. Ex: INT0 - INT255

INTERRUPT VECTOR TABLE

256 INTERRUPTS OF 8086 ARE DIVIDED IN TO 3 GROUPS

1. TYPE 0 TO TYPE 4 INTERRUPTS-These are used for fixed operations and hence are called

dedicated interrupts

2. TYPE 5 TO TYPE 31 INTERRUPTSNot Used By 8086,reserved For Higher Processors Like 8028680386 Etc

3. TYPE 32 TO 255 INTERRUPTSAvailable For User, called User Defined Interrupts These Can

Be H/W Interrupts And Activated Through Intr Line Or Can BeS/W Interrupts. 243

Type – 0 Divide Error Interrupt

Quotient is too large cant be fit in AL/AX or Divide By Zero {AX/0=∞}

Type –1 Single Step Interruptused for executing the program in single step mode by setting Trap Flag

To Set Trap Flag PUSHF MOV BP,SPOR [BP+0],0100H;SET BIT8POPF

Type – 2 Non Maskable InterruptThis Interrupt is used for executing ISR of NMI Pin (Positive Egde Signal). NMI cant be masked by S/W

Type – 3 Break Point Interruptused for providing BREAK POINTS in the program

Type – 4 Over Flow Interruptused to handle any Overflow Error after signed arithmetic

PRIORITY OF INTERRUPTS

Interrupt Type Priority

INT0, INT3-INT 255, Highest

NMI(INT2)

SINGLE STEP Lowest

Byte &String

Manipulation246

Refer String Instructions in Instruction SetSlide No: 160-163

Move, compare, store, load, scan

Byte ManipulationExample 1:

MOV AX,[1000]MOV BX,[1002]AND AX,BXMOV [2000],AXHLT

Example 2:MOV AX,[1000]MOV BX,[1002]OR AX,BXMOV [2000],AXHLT

Example 3:MOV AX,[1000]MOV BX,[1002]XOR AX,BXMOV [2000],AXHLT

Example 4:MOV AX,[1000]NOT AXMOV [2000],AXHLT

STRING MANIPULATION1. Copying a string (MOV SB)

MOV CX,0003 copy 3 memory locationsMOV SI,1000MOV DI,2000

L1 CLDMOV SBDEC CX decrement CXJNZ L1HLT

2. Find & Replace

UNIT-28086 SYSTEM BUS

STRUCTURE

Velalar College of Engg & Tech , Erode

DEPARTMENTS: CSE,IT {semester 04}ECE {semester 05}

Regulation : 2013

UNIT 2 Syllabus

8086 signals or

Pin Diagram

INTEL 8086-Pin Diagram/Signal Description

INTEL 8086 - Pin Details

Ground

ClockDuty cycle: 33%

Power Supply5V ± 10%

ResetRegisters, seg

regs, flags

CS: FFFFH, IP: 0000H

If high for minimum 4

Address/Data Bus:

Contains address bits A15-A0 when ALE is 1 & data bits D15 –

D0 when ALE is 0.

Address Latch Enable:

When high, multiplexed

address/data bus contains address

information.

INTERRUPT

Non - maskable interrupt

Interrupt request

Interrupt acknowledge

Direct Memory Access

Hold acknowledge

Address/Status Bus

Address bits A19 –A16 & Status bits S6

– S3

Bus High Enable/S7

Enables most significant data bits D15 – D8 during read or write operation.

S7: Always 1.

BHE#, A0:

0,0: Whole word (16-bits)

0,1: High byte to/from odd address

1,0: Low byte to/from even address

1,1: No selection

Min/Max modeMinimum Mode: +5VMaximum Mode: 0V

Minimum Mode Pins

Maximum Mode Pins

Minimum Mode- Pin Details

Read Signal

Write Signal

Memory or I/0

Data Bus Enable

Data Transmit/Receive

Maximum Mode - Pin Details

Status Signal

Inputs to 8288 to generate eliminated signals due to max

S2 S1 S0

000: INTA001: read I/O port010: write I/O port011: halt100: code access101: read memory110: write memory111: none -passive

DMA Request/Grant

Lock Output

Lock OutputUsed to lock peripheralsoff the system

Activated by using theLOCK: prefix on anyinstruction

Queue StatusUsed by numeric

coprocessor (8087)

QS1 QS000: Queue is idle

01: First byte of opcode

10: Queue is empty

11: Subsequent byte of opcode

GNDAD14AD13AD12AD11AD10

AD9AD8AD7AD6AD5AD4AD3AD2AD1AD0NMIINTR

CLKGND

VccAD15A16/S3A17/S4A18/S5A19/S6___BHE/S7 (HIGH)___MN/MX___RD ___ ____HOLD (RQ/GT0)___ ____HLDA (RQ/GT1)___ ______WR (LOCK)__ __IO/M (S2)__ __DT/R (S1)____ __DEN (S0)ALE (QS0)_____INTA (QS1)_____TESTREADYRESET

INTEL8086

Minmode operation signals (MN/MX=1)

Maxmode operation signals (MN/MX=0)

Time-multiplexed Address / Data Bus

(bidirectional)

Hardware interrupt

requests (inputs)

2...5MHz, 1/3 duty cycle

(input)

0V=“0”, reference

for all voltages

5V±10%

Time-multiplexed Address Bus

/Status signals(outputs)

Status signals

(outputs)

Operation Mode, (input):

1 = minmode (8088 generates all the needed control signals for a small

system),

0 = maxmode (8288 Bus

Controller expands the status signals to generate more

control signals)

Interrupt acknowledge

(output)

Control Bus

(in,out)

Timing Diagram

Basicsonly for understanding

System Timing DiagramsT-State:

— One clock period is referred to as a T-State

T-State

CPU Bus Cycle:— A bus cycle consists of 4 T-States

T1 T2 T3 T4

Signal Transition occurs when the clock signal is HIGH

Signal Transition occurs when the clock signal is LOW

Signal Transition occurs from HIGH to LOW on RISING EDGE

AD0-AD15

SYSTEM BUS TIMING

Memory Read Timing Diagrams

• Dump address on address bus.• Issue a read ( RD ) and set M/ IO to 1.• Wait for memory access cycle.

• Dump address on address bus.• Dump data on data bus.• Issue a write ( WR ) and set M/ IO to 1.

Memory Write Timing Diagrams

Bus TimingDuring T 1 :• The address is placed on the Address/Data bus.• Control signals M/ IO , ALE and DT/ R specify memory or I/O, latch the address

onto the address bus and set the direction of data transfer on data bus.During T 2 :• 8086 issues the RD or WR signal, DEN , and, for a write, the data.

• DEN enables the memory or I/O device to receive the data for writes and the 8086 to receive the data for reads.

During T 3 :• This cycle is provided to allow memory to access data.• READY is sampled at the end of T 2 .

• If low, T 3 becomes a wait state.• Otherwise, the data bus is sampled at the end of T 3 .

During T 4 :• All bus signals are deactivated, in preparation for next bus cycle.• Data is sampled for reads, writes occur for writes.

Setup & Hold Time

Setup time – The time before the rising edge of the clock, while the data must be valid and constantHold time – The time after the rising edge of the clock during which the data must remain valid and constant

WAIT State

• A wait state (Tw) is an extra clocking period, insertedbetween T2 and T3, to lengthen the bus cycle, allowingslower memory and I/O components to respond.

• The READY input is sampled at the end of T2, and again,if necessary in the middle of Tw. If READY is ‘0’ then aTw is inserted.

1 2 3 4 Clock

Basic configurations

BASIC CONFIGURATIONS-1.Minimum Mode 2.Maximum Mode– Minimum mode(MN/MX=Vcc)

• Pin #33 (MN/MX) connect to +5V• Pin 24-31 are used as memory and I/O control signal • The control signals are generated internally by the 8086/88 • More cost-efficient

– Maximum mode(MN/MX=GND)• Pin #33 (MN/MX) connect to Ground• Some control signals are generated externally by the 8288

bus controller chip• Max mode is used when math processor is used.

1.Minimum Mode

configuration

Minimum Mode 8086 System• 8086 is operated in minimum mode by

MN/MX pin to logic 1 ( Vcc ).• In this mode, all the control signals are given

out by the microprocessor chip itself.

285NOTE: Explain Minimum mode signals also {refer pin diagram}

MINIMUM MODE SIGNALS

Memory READ in Minimum Mode

Memory WRITE in Minimum Mode

2.Maximum Mode

configurationNOTE: Explain Maximum mode signals also {refer pin diagram}

MAXIMUM MODE SIGNALS

8288 – BUS CONTROLLER

MAXIMUM MODE

MULTIPROCESSOR CONFIGURATIONS

Multiprocessor configuration

Coprocessor 8087

Multiprocessor configuration• Multiprocessor Systems refer to the use of multiple

processors that executes instructions simultaneouslyand communicate with each other using mail boxes andSemaphores.

• Maximum mode of 8086 is designed to implement 3basic multiprocessor configurations:

1. Coprocessor (8087)2. Closely coupled (8089)3. Loosely coupled (Multibus)

• Coprocessors and Closely coupled configurations aresimilar in that both the 8086 and the external processorshares the:

- Memory- I/O system- Bus & bus control logic- Clock generator

Co-processor – Intel 8087

8087 instructions are inserted in the 8086 program

8086 and 8087 reads instruction bytes and puts them in the respective queues

8087 instructions have 11011 as the MSB of their first code byte

Coprocessor / Closely Coupled Configuration

TEST pin of 8086• Used in conjunction with the WAIT instruction in

multiprocessing environments.

• This is input from the 8087 coprocessor.

• During execution of a wait instruction, the CPU checks thissignal.

• If it is low, execution of the signal will continue; if not, itwill stop executing.

1.Coprocessor Execution ExampleCoprocessor cannot take control of the bus, it does everything through the CPU

2.Closely Coupled Execution Example

• Closely Coupled processor may take control of the bus independently.

• Two 8086’s cannot be closely coupled.

3.Loosely Coupled Configuration

• has shared system bus, system memory, and systemI/O.

• each processor has its own clock as well as its ownmemory (in addition to access to the system resources).

• Used for medium to large multiprocessor systems.

• Each module is capable of being the bus master.

• Any module could be a processor capable of being a busmaster, a coprocessor configuration or a closely coupledconfiguration.

Loosely Coupled Configuration• No direct connections between the modules.

• Each share the system bus and communicate throughshared resources.

• Processor in their separate modules can simultaneouslyaccess their private subsystems through their localbusses, and perform their local data references andinstruction fetches independently. This results inimproved degree of concurrent processing.

• Excellent for real time applications, as separate modulescan be assigned specialized tasks

BUS ALLOCATION SCHEMES:Three bus allocation schemes:1. Daisy Chaining2. Pooling3. Independent

1. Daisy Chaining:- Need a bus controller to monitor bus busy and bus request

signals- Sends a bus grant to a Master >> each Master either keeps the

service or passes it on- Controller synchronizes the clocks- Master releases the Bus Busy signal when finished

Daisy Chaining:

Independent

Advantages of Multiprocessor Configuration

1. High system throughput can be achieved by having more thanone CPU.

2. The system can be expanded in modular form.Each bus master module is an independent unit and normally resides ona separate PC board. One can be added or removed without affecting theothers in the system.

3. A failure in one module normally does not affect the breakdownof the entire system and the faulty module can be easilydetected and replaced

4. Each bus master has its own local bus to access dedicatedmemory or IO devices. So a greater degree of parallel processingcan be achieved.

INTRODUCTION TO ADVANCED PROCESSORS

Intel family of microprocessor, bus and memory sizes

Microprocessor

Data bus width

Address bus width

Memory size

80186 16 20 1M

80286 16 24 16M

80386 DX 32 32 4G80486 32 32 4G

Pentium 4 & core 2

64 40 1T

UNIT-3I/O

INTERFACING

Regulation : 2013

UNIT 3 Syllabus• Memory Interfacing & I/O interfacing• Parallel communication interface {8255 PPI}• Serial communication interface {8251 USART}• D/A and A/D Interface {ADC 0800/0809,DAC 0800}• Timer {or counter} – {8253/8254 Timer}• Keyboard /display controller {8279}• Interrupt controller {8259}• DMA controller {8237/8257}• Programming and applications Case studies

1.Traffic Light control 2.LED display 3.LCD display 4.Keyboard display interface 5.Alarm Controller

Data Transfers Synchronous ----- Usually occur when

peripherals are located within the same computer as the CPU. Close proximity allows all state bits change at same time on a common clock.

Asynchronous ----- Do not require that the source and destination use the same system clock.

MEMORY DEVICES I/O DEVICESPresented by C.GOKUL,AP/EEE , Velalar College of Engg & Tech, Erode

interface memory (RAM, ROM, EPROM'...) or I/O devices to 8086 microprocessor. Several memory chips or I/O devices can connected to a microprocessor. An address decoding circuit is used to select the required I/O device or a memory chip.

IO mapped IO V/s Memory Mapped IO

Memory Mapped IO

IO is treated as memory. 16-bit addressing. More Decoder Hardware. Can address 216=64k

locations. Less memory is available.

IO Mapped IO

IO is treated IO. 8- bit addressing. Less Decoder

Hardware. Can address 28=256

locations. Whole memory address

space is available.

Memory Mapped IO

• Memory Instructions are used.

• Memory control signals are used.

• Arithmetic and logic operations can be performed on data.

• Data transfer b/w register and IO.

IO Mapped IO

• Special Instructions are used like IN, OUT.

• Special control signals are used.

• Arithmetic and logic operations can not be performed on data.

• Data transfer b/w accumulator and IO.

Parallel communication interface

INTEL 8255

Presented by C.GOKUL,AP/EEE , Velalar College of Engg & Tech, Erode

8255 PPI• The 8255 chip is also called as Programmable

Peripheral Interface. • The Intel’s 8255 is designed for use with Intel’s

8-bit, 16-bit and higher capability microprocessors

• The 8255 is a 40 pin integrated circuit (IC), designed to perform a variety of interface functions in a computer environment.

• It is flexible and economical.

PIN DIAGRAM OF 8255328

Signals of 8085329

8255 PIO/PPI It has 24 input/output lines which may be

individually programmed. 2 groups of I/O pins are named as

Group A (Port-A & Port C Upper)Group B (Port-B & Port C Lower)

3 ports(each port has 8 bit)Port A lines are identified by symbols PA0-PA7

Port B lines are identified by symbols PB0-PB7

Port C lines are identified by PC0-PC7 , PC3-PC0ie: PORT C UPPER(PC7-PC4) , PORT C LOWER(PC3-PC0)

D0 - D7: data input/output lines for the device. All information read from and written to the 8255 occurs via these 8 data lines.

CS (Chip Select). If this line is a logical 0, the microprocessor can read and write to the 8255.

RESET : The 8255 is placed into its reset state if this input line is a logical 1

• RD : This is the input line driven by the microprocessor and should be low to indicate read operation to 8255.

• WR : This is an input line driven by the microprocessor. A low on this line indicates write operation.

• A1-A0 : These are the address input lines and are driven by the microprocessor.

Control Logic CS signal is the master Chip Select A0 and A1 specify one of the two I/O Ports

CS A1 A0 Selected0 0 0 Port A0 0 1 Port B0 1 0 Port C0 1 1 Control

Register1 X X 8255 is not

selected

Block Diagram of 8255A 334

Block Diagram of 8255 (Architecture)

It has a 40 pins of 4 parts.1. Data bus buffer2. Read/Write control logic3. Group A and Group B controls4. Port A, B and C

1. Data bus buffer This is a tristate bidirectional buffer used

to interface the 8255 to system data bus. Data is transmitted or received by the buffer on execution of input or output instruction by the CPU.

2. Read/Write control logic This unit accepts control signals ( RD, WR ) and

also inputs from address bus and issues commands to individual group of control blocks ( Group A, Group B).

It has the following pins.

CS , RD , WR , RESET , A1 , A0

3. Group A and Group B controls• These block receive control from the CPU

and issues commands to their respective ports.Group A - PA and PCU ( PC7 –PC4)Group B – PB and PCL ( PC3 –PC0)

a) Port A: This has an 8 bit latched/buffered O/P and 8 bit input latch. It can be programmed in 3 modes – mode 0, mode 1, mode 2.

b) Port B: It can be programmed in mode 0, mode1

c) Port C : It can be programmed in mode 0

Modes of Operation of 8255

Bit Set/Reset(BSR) Mode Set/Reset bits in Port C

I/O Mode Mode 0 (Simple input/output) Mode 1 (Handshake mode) Mode 2 (Bidirectional Data Transfer)

1. BSR Mode342

B3 B2 B1 Bit/pin of port C selected

0 0 0 PC0

0 0 1 PC1

0 1 0 PC2

0 1 1 PC3

1 0 0 PC4

1 0 1 PC5

1 1 0 PC6

1 1 1 PC7

Concerned only with the 8-bits of Port C.Set or Reset by control wordPorts A and B are not affected

a) Mode 0 (Simple Input or Output):

• Ports A and B are used as Simple I/O Ports

• Port C as two 4-bit ports

• Features– Outputs are latched– Inputs are not latched– Ports do not have handshake or

interrupt capability

2. I/O MODE 344

b) Mode 1: (Input or Output with Handshake)

• Handshake signals are exchanged between MPU & Peripherals

• Features– Ports A and B are used as Simple I/O Ports– Each port uses 3 lines from Port C as

handshake signals– Input & Output data are latched– interrupt logic supported

c) Mode 2: Bidirectional Data Transfer

• Used primarily in applications such as data transfer between two computers

• Features– Ports A can be configured as the bidirectional

Port– Port B in Mode 0 or Mode 1.– Port A uses 5 Signals from Port C as handshake

signals for data transfer– Remaining 3 Signals from Port C Used as –

Simple I/O or handshake for Port B

Find control word(1) Port A: output with handshake (2) Port B: input with handshake (3) Port CL: output (4)Port CU: input

Solution:

1 0 1 0 1 1 1 0 = AEH

Port A: Output, Port B: Output, Port CU: Output, Port CL: Output

Solution:

1 0 0 0 0 0 0 0 = 80H

The control word register for the above ports of Intel 8255 is 80H.

Port A: Input, Port B: Input, Port CU: Input, Port CL: Input

Solution:

1 0 0 1 1 0 1 1 = 9BH

The control word register for the above ports of intel 8255 is 9BH.

Basics of serial communication1. Transmitter:- A parallel-in, serial-out shift register

2. Receiver:- A serial-in, parallel-out shift register.

Parallel Transfer

TRANSMITTER

Receiver

Serial communicationinterface

INTEL 8251 USART

UNIVERSAL SYNCHRONOUS ASYNCHRONOUS RECEIVER

TRANSMITTER (USART) Programmable chip designed for

synchronous and asynchronous serial data transmission

28 pin DIP Coverts the parallel data into a serial stream

of bits suitable for serial transmission. Receives a serial stream of bits and convert

it into parallel data bytes to be read by a microprocessor.

BLOCK DIAGRAM 356

Five Sections– Read/Write Control Logic

• Interfaces the chip with MPU• Determine the functions according to the control word • Monitors data flow

– Transmitter• Converts parallel word received from MPU into serial bits• Transmits serial bits over TXD line to a peripheral.

– Receiver• Receives serial bits from peripheral• Converts serial bits into parallel word• Transfers the parallel word to the MPU

– Data Bus Buffer- 8 bit Bidirectional bus.– Modem Controller

• Used to establish data communication modems over telephone line

Input Signals

CS – Chip Select When this signal goes low, 8251 is selected by

MPU for communication C/D – Control/Data

When this signal is high, the control registeror status register is addressed

When it is low, the data buffer is addressed Control and Status register is differentiated by

WR and RD signals, respectively

• WR – Write– writes in the control register or sends outputs to the

data buffer.– This connected to IOW or MEMW

• RD – Read– Either reads a status from status register or accepts

data from the data buffer– This is connected to either IOR or MEMR

• RESET - Reset• CLK - Clock

– Connected to system clock– Necessary for communication with microprocessor.

CS C/D RD WR Function0 1 1 0 MPU writes instruction in the

control register0 1 0 1 MPU reads status from the status

register 0 0 1 0 MPU outputs the data to the Data

Buffer0 0 0 1 MPU accepts data from the Data

Buffer1 X X X USART is not Selected

• Control Register– 16-bit register– This register can be accessed an output port

when the C/D pin is high

• Status Register– Checks ready status of a peripheral

• Data Buffer

Transmitter Section

Accepts parallel data and converts it into serial data

Two registers Buffer Register

To hold eight bits

Output Register Converts eight bits into a stream of serial bits

Transmits data on TxD pin with appropriate framing bits(Start and Stop)

Signals Associated with Transmitter Section

• TxD – Transmit Data– Serial bits are transmitted on this line

• TxC – Transmitter Clock– Controls the rate at which bits are transmitted

• TxRDY – Transmitter Ready– Can be used either to interrupt the MPU or

indicate the status• TxE – Transmitter Empty

– Logic 1 on this line indicate that the output register is empty

Receiver Section

Accepts serial data from peripheral and converts it into parallel data

The section has two registers Input Register Buffer Register

Signals Associated with Receiver Section

RxD – Receive Data Bits are received serially on this line and

converted into parallel byte in the receiver input

RxC – Receiver Clock RxRDY – Receiver Ready

It goes high when the USART has a character in the buffer register and is ready to transfer it to the MPU

Signals Associated with Modem Control

• DSR- Data Set Ready– Normally used to check if the Data Set is ready when

communicating with a modem• DTR – Data Terminal Ready

– device is ready to accept data when the 8251 is communicating with a modem.

• RTS – Request to send Data– the receiver is ready to receive a data byte from

modem• CTS – Clear to Send

Control words367

Interfacing of 8255(PPI) with 8085 processor: 372

11-374

Programming 8251 8251 mode register

7 6 5 4 3 2 1 0 Mode register

Number of Stop bits

00: invalid01: 1 bit10: 1.5 bits11: 2 bits

Parity0: odd1: even

Parity enable0: disable1: enable

Character length00: 5 bits01: 6 bits10: 7 bits11: 8 bits

Baud Rate00: Syn. Mode01: x1 clock10: x16 clock11: x64 clock

11-375

8251 command register

EH IR RTS ER SBRK RxE DTR TxE command register

TxE: transmit enableDTR: data terminal ready, DTR pin will be lowRxE: receiver enableSBPRK: send break character, TxD pin will be lowER: error resetRTS: request to send, CTS pin will be lowIR: internal resetEH: enter hunt mode (1=enable search for SYN character)

11-376

8251 status register

DSR SYNDET FE OE PE TxEMPTY RxRDY TxRDY status register

TxRDY: transmit readyRxRDY: receiver readyTxEMPTY: transmitter emptyPE: parity errorOE: overrun errorFE: framing errorSYNDET: sync. character detectedDSR: data set ready

The analog to digital converter chips 0808and 0809 are 8-bit CMOS,successive approximation converters.

Successive approximation technique is one of the fast techniques for analog to digital conversion. The conversion delay is 100 µsat a clock frequency of 640 kHz.

The digital to analog converters convert binary numbers into their analog equivalent voltages or currents. Techniques are employed for digital to analog conversion.

i. Weighted resistor network ii. R-2R ladder network iii. Current output D/A converter

The DAC find applications in areas like digitally controlled gains, motor speed control, programmable gain amplifiers, digital voltmeters, panel meters, etc.

In a compact disk audio player for example a 14 or16-bit D/A converter is used to convert the binary data read off the disk by a laser to an analog audio signal.

Characteristics :1. Resolution: It is a change in analog output for one LSB change in digital input.It is given by(1/2^n )*Vref. If n=8 (i.e.8-bit DAC)

1/256*5V=39.06mV2. Settling time: It is the time required for the DAC to settle for a full scale code change.

DAC 0800 8-bit Digital to Analog converter

Features: i. DAC0800 is a monolithic 8-bit DAC manufactured by

National semiconductor. ii. It has settling time around 100ms iii. It can operate on a range of power supply voltage i.e.

from 4.5V to +18V. Usually the supply V+ is 5V or +12V. The V- pin can be kept at a minimum of -12V.

iv. Resolution of the DAC is 39.06mV

TIMER/COUNTER

RD: read signal WR: write signal CS: chip select signal A0, A1: address lines Clock :This is the clock input for the counter.

The counter is 16 bits. Out :This single output line is the signal that

is the final programmed output of the device. Gate :This input can act as a gate for the

clock input line, or it can act as a start pulse,

8254 Programming

11-394

8254 ModesGate is low the count will be paused

Gate is highWill continuecounting

Mode 0: An events counter enabled with G.

Mode 1: One-shot mode. s

Gate isHigh outputwill be high

Counter will be reloadedAfter gate high.

Mode 2: Counter generates a series of pulses 1 clock pulse wide

Mode 3: Generates a continuous square-wave with G set to 1

cycle is repeated untilreprogrammed or G pin set to 0

If count is even, 50% duty cycleotherwise OUT is high 1 cycle longer

Mode 4: Software triggered one-shot.

Mode 5: Hardware triggered one-shot. G controls similar to Mode 1.

In the last countingWill be stop(not repeated)

In the last countOut will be low

Keyboard/Display Controller

INTEL 8279

The INTEL 8279 is specially developed for interfacing keyboard and display devices to 8085/8086 microprocessor based system

Simultaneous keyboard and display operations

Scanned keyboard mode Scanned sensor mode 8-character keyboard FIFO 1 6-character display

Keyboard section Display section Scan section CPU interface section

The keyboard section consists of 8 return lines RL0 - RL7 that can be used to form the columns of a keyboard matrix.

It has two additional input : shift and control/strobe. The keys are automatically debounced.

The two operating modes of keyboard section are 2-key lockout and N-key rollover.

In the 2-key lockout mode, if two keys are pressed simultaneously, only the first key is recognized.

In the N-key rollover mode simultaneous keys are recognized and their codes are stored in FIFO.

The keyboard section also have an 8 x 8 FIFO (First In First Out) RAM.

The FIFO can store eight key codes in the scan keyboard mode. The status of the shift key and control key are also stored along with key code. The 8279 generate an interrupt signal (IRQ)when there is an entry in FIFO.

The display section has eight output lines divided into two groups A0-A3 and B0-B3.

The output lines can be used either as a single group of eight lines or as two groups of four lines, in conjunction with the scan lines for a multiplexed display.

The output lines are connected to the anodes through driver transistor in case of common cathode 7-segment LEDs.

The cathodes are connected to scan lines through driver transistors.

The display can be blanked by BD (low) line.

The display section consists of 16 x 8 display RAM. The CPU can read from or write into any location of the display RAM.

The scan section has a scan counter and four scan lines, SL0 to SL3.

In decoded scan mode, the output of scan lines will be similar to a 2-to-4 decoder.

In encoded scan mode, the output of scan lines will be binary count, and so an external decoder should be used to convert the binary count to decoded output.

The scan lines are common for keyboard and display.

The CPU interface section takes care of data transfer between 8279 and the processor.

This section has eight bidirectional data lines DB0 to DB7 for data transfer between 8279 and CPU.

It requires two internal address A =0 for selecting data buffer and A = 1 for selecting control register of8279.

The control signals WR (low), RD (low), CS (low) and A0 are used for read/write to 8279.

It has an interrupt request line IRQ, for interrupt driven data transfer with processor.

The 8279 require an internal clock frequency of 100 kHz. This can be obtained by dividing the input clock by an internal prescaler.

All the command words or status words are written orread with A0 = 1 and CS = 0 to or from 8279.

a) Keyboard Display Mode Set : The format of the command word to select different modes of operation of 8279 is given below with its bit definitions.

D7 D6 D5 D4 D3 D2 D1 D0

0 0 0 D D K K K

SENSOR MATRIX

B) Programmable clock :

The clock for operation of 8279 is obtained by dividing the external clock input signal by a programmable constant called prescaler. PPPPP is a 5-bit binary constant. The input frequency is divided by a decimal constant ranging from 2 to 31, decided by the bits of an internal prescaler, PPPPP.

D7 D6 D5 D4 D3 D2 D1 D0

0 0 1 P P P P P

c) Read FIFO / Sensor RAM : The format of this command is given below.

AI – Auto Increment FlagAAA – Address pointer to 8 bit FIFO RAM

X- Don’t careThis word is written to set up 8279 for reading FIFO/ sensor RAM. In scanned keyboard mode, AI and AAA bits are of no use. The 8279 will automatically drive data bus for each subsequent read, in the same sequence, in which the data was entered.In sensor matrix mode, the bits AAA select one of the 8 rows of RAM. If AI flag is set, each successive read will be from the subsequent RAM location.

D7 D6 D5 D4 D3 D2 D1 D0

0 1 0 AI X A A A

d) Read Display RAM : This command enables a programmer to read the display RAM data.

The CPU writes this command word to 8279 to prepare it for display RAM read operation. AI is auto increment flag and AAAA, the 4-bit address points to the 16-byte display RAM that is to be read.If AI=1, the address will be automatically, incremented after each read or write to the Display RAM. The same address counter is used for reading and writing.

D7 D6 D5 D4 D3 D2 D1 D0

0 1 1 AI A A A A

d) Write Display RAM : This command enables a programmer to write the display RAM data.

AI – Auto increment Flag.AAAA – 4 bit address for 16-bit display RAM to be

written.e) Display Write Inhibit/Blanking :

D7 D6 D5 D4 D3 D2 D1 D0

1 0 0 AI A A A A

D7 D6 D5 D4 D3 D2 D1 D0

1 0 1 X IW IW BL BL

IW - inhibit write flag BL - blank display bit flags

g) Clear Display RAM :

ENABLES CLEAR DISPLAY WHEN CD2=1

• CD2 must be 1 for enabling the clear display command.• If CD2 = 0, the clear display command is invoked by setting CA(CLEAR ALL) =1 and maintaining CD1, CD0 bits exactly same as above. • If CF(CLEAR FIFO RAM STATUS) =1, FIFO status is cleared and IRQ line is pulled down and the sensor RAM pointer is set to row 0. •If CA=1, this combines the effect of CD and CF bits.

D7 D6 D5 D4 D3 D2 D1 D0

1 1 0 CD2 CD1 CD0 CF CA

CD2 CD1 CD0

0X - All zeros ( x don’t care ) AB=0010 - A3-A0 =2 (0010) and B3-B0=00 (0000)11 - All ones (AB =FF), i.e. clear RAM

h) End Interrupt / Error mode Set :

E- Error modeX- don’t care

For the sensor matrix mode, this command lowers the IRQ line and enables further writing into the RAM. Otherwise, if a change in sensor value is detected, IRQ goes high that inhibits writing in the sensor RAM. For N-Key roll over mode, if the E bit is programmed to be ‘1’, the 8279 operates in special Error mode

D7 D6 D5 D4 D3 D2 D1 D0

1 1 1 E X X X 1

INTERRUPT CONTROLLER

1. This IC is designed to simplify the implementation of the interrupt interface in the 8088

and 8086 based microcomputer systems.

2. This device is known as a ‘Programmable Interrupt Controller’ or PIC.3. It is manufactured using the NMOS technology and It is available in 28-pin DIP.4. The operation of the PIC is programmable under software control (Programmable)and it

can be configured for a wide variety of applications.

5. 8259A is treated as peripheral in a microcomputer system.

6. 8259A PIC adds eight vectored priority encoded interrupts to the microprocessor.

7. This controller can be expanded without additional hardware to accept up to 64

interrupt request inputs. This expansion required a master 8259A and eight 8259A

slaves.

8. Some of its programmable features are:

· The ability to accept level-triggered or edge-triggered inputs.

· The ability to be easily cascaded to expand from 8 to 64 interrupt-inputs.

· Its ability to be configured to implement a wide variety of priority schemes.

8259 Programmable Interrupt Controller (PIC)

8259A PIC- PIN DIGRAM

ASSINGMENT OF SIGNALS FOR 8259: 1. D7- D0 is connected to microprocessor data bus D7-D0 (AD7-AD0).2. IR7- IR0, Interrupt Request inputs are used to request an interrupt and to connect to a slave

in a system with multiple 8259As.3. WR - the write input connects to write strobe signal of microprocessor.4. RD - the read input connects to the IORC signal.5. INT - the interrupt output connects to the INTR pin on the microprocessor from the master,

and is connected to a master IR pin on a slave.6. INTA - the interrupt acknowledge is an input that connects to the INTA signal on the system.

In a system with a master and slaves, only the master INTA signal is connected.7. A0 - this address input selects different command words within the 8259A.8. CS - chip select enables the 8259A for programming and control.9. SP/EN - Slave Program/Enable Buffer is a dual-function pin.

When the 8259A is in buffered mode, this pin is anoutput that controls the data bus transceivers in alarge microprocessor-based system.

When the 8259A is not in buffered mode, this pinprograms the device as a master (1) or a slave (0).

CAS2-CAS0, the cascade lines are used as outputs fromthe master to the slaves for cascading multiple8259As in a system.

8259A PIC- BLOCK DIAGRAM

The 82C59A accepts two types of command words generated by theCPU:1. Initialization Command Words (ICWs):

Before normal operation can begin, each 82C59A in thesystem must be brought to a starting point - by a sequence of 2 to4 bytes timed by WR pulses.

2. Operational Command Words (OCWs):These are the command words which command the 82C59A

to operate in various interrupt modes. Among these modes are:a. Fully nested mode.b. Rotating priority mode.c. Special mask mode.d. Polled mode.

The OCWs can be written into the 82C59A anytime afterinitialization.

Programming the 8259A: -

To program this ICW for 8086 we place a logic 1 in bit IC4.

Bits D7, D6 , D5and D2 are don’t care for microprocessor operation and only

apply to the 8259A when used with an 8-bit 8085 microprocessor.

This ICW selects single or cascade operation by programming the SNGL bit. If

cascade operation is selected, we must also program ICW3.

The LTIM bit determines whether the interrupt request inputs are positive edge

triggered or level-triggered.

Selects the vector number used with the interrupt request inputs.

For example, if we decide to program the 8259A so that it functions at vector

locations 08H-0FH, we place a 08H into this command word.

Likewise, if we decide to program the 8259A for vectors 70H-77H, we place a

70H in this ICW.

Is used only when ICW1 indicates that the system is operated in cascade mode.

This ICW indicates where the slave is connected to the master.

For example, if we connected a slave to IR2, then to program ICW3 for this

connection, in both master and slave, we place a 04H in ICW3.

Suppose we have two slaves connected to a master using IR0 and IR1. The

master is programmed with an ICW3 of 03H; one slave is programmed with an

ICW3 of 01H and the other with an ICW3 of 02H.

Is programmed for use with the 8088/8086. This ICWis not programmed in a system that functions with the8085 microprocessors.

The rightmost bit must be logic 1 to select operationwith the 8086 microprocessor, and the remaining bitsare programmed as follows:

Is used to set and read the interrupt mask register.

When a mask bit is set, it will turn off (mask) the corresponding

interrupt input. The mask register is read when OCW1 is read.

Because the state of the mask bits is known when the 8259A is

first initialized, OCW1 must be programmed after programming

the ICW upon initialization.

Operation Command Words

Is programmed only when the AEOI mod is not selected for the 8259A.

In this case, this OCW selects how the 8259A responds to an interrupt.

The modes are listed as follows in next slide:

Selects the register to be read, the operation of the special mask register, and

the poll command.

If polling is selected, the P-bit must be set and then output to the 8259A. The

next read operation would read the poll word. The rightmost three bits of the

poll word indicate the active interrupt request with the highest priority.

The leftmost bit indicates whether there is an interrupt, and must be checked

to determine whether the rightmost three bits contain valid information.

8237DMA CONTROLLER

Introduction: Direct Memory Access (DMA) is a method of allowing data

to be moved from one location to another in a computerwithout intervention from the central processor (CPU).

It is also a fast way of transferring data within (andsometimes between) computer.

The DMA I/O technique provides direct access to thememory while the microprocessor is temporarily disabled.

The DMA controller temporarily borrows the address bus,data bus and control bus from the microprocessor andtransfers the data directly from the external devices to aseries of memory locations (and vice versa).

The 8237 DMA controller• Supplies memory and I/O with control signals and addresses during DMA

transfer• 4-channels (expandable)

– 0: DRAM refresh– 1: Free– 2: Floppy disk controller– 3: Free

• 1.6MByte/sec transfer rate• 64 KByte section of memory address capability with single programming• “fly-by” controller (data does not pass through the DMA-only memory to I/O

transfer capability)• Initialization involves writing into each channel:

• i) The address of the first byte of the block of data that must be transferred (called the base address).

• ii) The number of bytes to be transferred (called the word count).

8237 pins• CLK: System clock• CS΄: Chip select (decoder output)• RESET: Clears registers, sets mask register• READY: 0 for inserting wait states• HLDA: Signals that the μp has relinquished buses• DREQ3 – DREQ0: DMA request input for each channel• DB7-DB0: Data bus pins• IOR΄: Bidirectional pin used during programming and during a DMA write cycle• IOW΄: Bidirectional pin used during programming and during a DMA read cycle• EOP΄: End of process is a bidirectional signal used as input to terminate a DMA process or

as output to signal the end of the DMA transfer• A3-A0: Address pins for selecting internal registers• A7-A4: Outputs that provide part of the DMA transfer address• HRQ: DMA request output• DACK3-DACK0: DMA acknowledge for each channel.• AEN: Address enable signal• ADSTB: Address strobe• MEMR΄: Memory read output used in DMA read cycle• MEMW΄: Memory write output used in DMA write cycle

8237 block diagram

Block Diagram Description

It containing Five main Blocks.1. Data bus buffer2. Read/Control logic3. Control logic block4. Priority resolver5. DMA channels.

DATA BUS BUFFER: It contain tristate ,8 bit bi-directional buffer. Slave mode ,it transfer data between

microprocessor and internal data bus. Master mode ,the outputs A8-A15 bits of

memory address on data lines (Unidirectional).

READ/CONTROL LOGIC: It control all internal Read/Write operation. Slave mode ,it accepts address bits and control

signal from microprocessor. Master mode ,it generate address bits and control

signal.459

Control logic block It contains ,1. Control logic2. Mode set register and 3. Status Register.

CONTROL LOGIC: Master mode ,It control the sequence of DMA

operation during all DMA cycles. It generates address and control signals. It increments 16 bit address and decrement 14 bit

counter registers. It activate a HRQ signal on DMA channel Request. Slave ,mode it is disabled.

DMA controller details

Programming and applications Case

studies1.Traffic Light control

2.LED display 3.LCD display

4.Keyboard display interface 5.Alarm Controller462

1. TRAFFIC LIGHT

CONTROL463

Traffic lights, which may also be known as stoplights, traffic lamps, traffic signals, signal lights, robots or semaphore, are signaling devices positioned at road intersections, pedestrian crossings and other locations to control competing flows of traffic.

INTERFACING TRAFFIC LIGHT WITH 8086The Traffic light controller section consists of 12 Nos.

point led’s arranged by 4Lanes in Traffic light interface card. Each lane has Go(Green), Listen(Yellow) and Stop(Red) LED is being placed.

LAN Direction 8086 LINES MODULES

CIRCUIT DIAGRAM TO INTERFACE TRAFFIC LIGHT WITH 8086

8086 ALP:1100: START: MOV BX, 1200H

MOV CX, 0008HMOV AL,[BX]MOV DX, CONTROL PORTOUT DX, ALINC BX

NEXT: MOV AL,[BX]MOV DX, PORT AOUT DX,ALCALL DELAYINC BXLOOP NEXTJMP START

DELAY: PUSH CXMOV CX,0005H

REPEAT: MOV DX,0FFFFHLOOP2: DEC DX

JNZ LOOP2LOOP REPEATPOP CXRET

Lookup Table 1200 80H

1201 21H,09H,10H,00H (SOUTH WAY) 1205 0CH,09H,80H,00H (EAST WAY) 1209 64H,08H,00H,04H (NOURTH WAY) 120D 24H,03H,02H,00H (WEST WAY) 1211 END

2. LED DISPLAY

Light Emitting Diodes (LED) is the most commonly used components, usually for displaying pins digital states. Typical uses of LEDs include alarm devices, timers and confirmation of user input such as a mouse click or keystroke.

INTERFACING LEDAnode is connected through a resistor to GND & the

Cathode is connected to the Microprocessor pin. So when the Port Pin is HIGH the LED is OFF & when the Port Pin is LOW the LED is turned ON.

PIN ASSIGNMENT WITH 8086

INTERFACE LED WITH 8255

8086 ALP LED interface1100: START: MOV AL, 80

MOV DX, FF36 OUT DX, AL

BEGIN: MOV AL, 00MOV DX, FF30OUT DX, ALCALL DELAYMOV AL, FFOUT DX, ALCALL DELAYJMP BEGIN

DELAY: MOV CX, FFFFPO: DEC CX

JNE PORET

3. LCD DISPLAY

HARDWARE CONFIGURATION OF LCD WITH 8051/8086/8085

LCD INTERFACING WITH 8086 TRAINER KIT

GPIO- I (8255) J1 Connector PORTS ADDRESS

Control port FF26PORT A FF20PORT B FF22PORT C FF24

GPIO- I (8255) J4 Connector PORTS ADDRESS

LCD INTERFACING WITH 8051 TRAINER KIT GPIO- I (8255) J1 Connector

PORTS ADDRESSControl port 4003PORT A 4000PORT B 4001PORT C 4002

Used in UNIT 5 also

4. Keyboard display interface

HARDWARE DESCRIPTION OF 8279 INTERFACE CARDKeyboard and display is configured in the encoded mode.

In the encoded mode, a binary count sequence is put on the scan lines SL0-SL3.These lines must be externally decoded to provide the scan lines for keyboard and display. A 3 to 8 decoder 74LS138 is provided for this purpose. The S0-S1 output lines of this decoder are connected to the two rows of the keyboard. And QA0 to QA7 is connected to 7 Segment Display

PIN DIAGRAM OF 8279 PIN DIAGRAMOF 74LS138

MVI A, 00H Initialize keyboard/display in encodedOUT 81H scan keyboard 2 key lockout modeMVI A, 34H

OUT 81H Initialize prescaler countMVI A, 0BH Load mask pattern to enable RST 7.5SIM mask other interruptsEI Enable Interrupt

HERE: JMP HERE Wait for the interruptInterrupt service routine

MVI A, 40H Initialize 8279 in read FIFO RAM modeOUT 81H

IN 80H Get keycodeMVI H, 62H Initialize memory pointer to pointMOV L, A 7-Segment codeMVI A, 80H : Initialize 8279 in write display RAM modeOUT 81H

MOV A, M : Get the 7 segment codeOUT 80H : Write 7-segment code in display RAMEI : Enable interruptRET : Return to main program

5. ALARM CONTROLLER

Relevant MaterialNot exact

GPIO- I J1 Connecter PORTS ADDRESS

GPIO- II J1 Connecter PORTS ADDRESS

BasicsMicroprocessor &Microcontroller

What is Microcontroller?

Micro Controller

Very Small A mechanism that controls the operation of a machine

CPU for Computers No RAM, ROM, I/O on CPU chip itself Example: Intel's x86, Motorola’s 680x0

A smaller computer On-chip RAM, ROM, I/O ports... Example: Motorola’s 6811, Intel’s 8051, Zilog’s

Z8 and PIC

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

General-purpose

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

Not Expansive

Single-purpose

Home Appliances, intercom, telephones, security systems, garage door

openers, answering machines, fax machines, home computers,TVs, cable TV tuner, VCR, camcorder, remote controls, videogames, cellular phones, musical instruments, sewing machines,lighting control, paging, camera, pinball machines, toys, exerciseequipment etc.

Office Telephones, computers, security systems, fax machines,

microwave, copier, laser printer, color printer, paging etc.

Auto Trip computer, engine control, air bag, ABS, instrumentation,

security system, transmission control, entertainment, climatecontrol, cellular phone, keyless entry

Regulation : 2013

UNIT 4 Syllabus

• Architecture of 8051• Special Function Registers(SFRs)• I/O Pins Ports and Circuits {Pin Diagram}• Instruction set• Addressing modes • Assembly language programming

The 8051 is a subset of the 8052 The 8031 is a ROM-less 8051

Add external ROM to it You lose two ports, and leave only 2 ports for I/O

operations

Intel introduced 8051, developed in the year1981.

The 8051 is an 8-bit controller. D0-D7 DATA LINES A0-A15 ADDRESS LINES

InterruptControl

8bitCPU

256 BRAM

OSCBus

Control 4 I/O Ports SerialPort

Timer 1

Timer 0

General Block Diagram of 8051

TXD RXDP0 P1 P2 P3

External Interrupts

CounterInputs

8 bit CPU On-chip clock oscillator 4K bytes of on-chip Program Memory-ROM 128 bytes of on-chip Data RAM 64KB Program Memory address space 64KB Data Memory address space 32 bidirectional I/0 lines (Port 0,1,2,3)

Port 0 { P0.0-P0.7 } – 8 pinsPort 1 { P1.0-P1.7 } – 8 pinsPort 2 { P2.0-P2.7 } – 8 pinsPort 3 { P3.0-P3.7 } – 8 pins

Two 16-bit timer/counters(Timer 1,Timer 0) One serial port

UART(Universal Asynchronous Receiver Transmitter) 6-source interrupt structure

1. External interrupt INT02. Timer interrupt T03. External interrupt INT14. Timer interrupt T15. Serial communication interrupt6. Timer Interrupt T2

4 Register Banks (Bank 0, Bank 1, Bank 2, Bank 3) each bank has R0-R7 registers

Pin Description of the 8051

orIO Port structure

EA/VPP

• EA, “external access’’

• EA = 0, 8051 microcontroller access fromexternal program memory (ROM) only.

• EA = 1, then it access internal and externalprogram memories (ROMS).

I/O Port Pins

• The four 8-bit I/O ports

Port 0 { P0.0-P0.7 } – 8 pinsPort 1 { P1.0-P1.7 } – 8 pinsPort 2 { P2.0-P2.7 } – 8 pinsPort 3 { P3.0-P3.7 } – 8 pins

Port 3

• Port 3 can be used as input or output.

• Port 3 has the additional function ofproviding some extremely importantsignals

Pin Description SummaryPIN TYPE NAME AND FUNCTION

Vss I Ground: 0 V reference.

Vcc I Power Supply + 5V.

P0.0 - P0.7I/O Port 0: Port 0 is also the multiplexed low-order address and

data bus during accesses to external program and datamemory.

P1.0 - P1.7I/O Port 1: Port 1 is an 8-bit bi-directional simple I/O port.

P2.0 - P2.7

I/O Port 2: Port 2 is an 8-bit bidirectional I/O. Port 2 emits thehigh order address byte

P3.0 - P3.7I/O Port 3: Port 3 is an 8 bit bidirectional I/O port. Port 3 also

serves special features as explained.511

Pin Description SummaryPIN TYPE NAME AND FUNCTION

RST I Reset: resets the device.

ALE O Address Latch Enable:When ALE=0, it provides data D0-D7When ALE=1, it has address A0-A7

PSEN* O Program Store Enable:For External Code Memory, PSEN = 0For External Data Memory, PSEN = 1

EA*/VPP I External Access Enable/Programming Supply Voltage:EA = 0, 8051 microcontroller access from externalprogram memory (ROM) only.

EA = 1, then it access internal and external programmemories (ROMS).

Architecture of 8051

microcontroller

Program Counter(PC) : The program counter always points to the address of the next instruction to be executed.Stack Pointer Register (SP) : It is an 8-bit register which stores the address of the stack top.ALU: perform arithmetic & logical operations

Flags : Carry(C),Auxiliary Carry(AC), Overflow(O) & Parity(P)

Timing & Control: Timing and control unit synchronises all microcontroller operations with clock & generates control signals.

DPTR: (Data Pointer) - 16 bit DPH-Data Pointer High – 8 bit DPL-Data Pointer Low – 8 bit

DPTR Register is usually used for storing data and intermediate results.

8051 Program Memory,

Data Memory structure

8051 Memory Structure

EXT INT 128

Program Memory Data Memory

64K 64K

EA = 0 EA = 1

Special Function

Registers [SFR]520

• A Register (Accumulator)• B Register• Program Status Word (PSW) Register• Data Pointer Register (DPTR)

– DPH (Data Pointer High) , DPL(Data Pointer Low)• Stack Pointer (SP) Register• P0, P1, P2, P3 - Input/output port Registers• Timer T0 - TH0 & TL0• Timer T1 – TH1 & TL1• Timer Control (TCON) Register• Serial Port Control (SCON) Register• Serial Buffer Control (SBUF) Register• IP Register (Interrupt Priority)• IE Register (Interrupt Enable)

8051 Register Bank Structure4 MEMORY BANKS

Bank 0

R0 R1 R2 R3 R4 R5 R6 R7Bank 3

R0 R1 R2 R3 R4 R5 R6 R7

Program Status Word [PSW]

C AC F0 RS1 RS0 OV F1 P

Register Bank Select

Auxiliary Carry

User Flag 0

Parity

User Flag 1

Overflow

00-Bank 001-Bank 110-Bank 211-Bank 3

Data Pointer Register (DPTR)It consists of two separate registers: DPH (Data Pointer High) &DPL (Data Pointer Low).

Stack Pointer (SP) Register

P0, P1, P2, P3 – Input / Output Registers

INSTRUCTION SET OF 8051

8051 Instruction Set• The instructions are grouped into 5 groups

– Arithmetic– Logic– Data Transfer– Boolean– Branching

1. Arithmetic Instructions• ADD A, source

A ← A + <operand>.

• ADDC A, sourceA ← A + <operand> + CY.

• SUBB A, sourceA ← A - <operand> - CY{borrow}.

• INC– Increment the operand by one. Ex: INC DPTR

• DEC– Decrement the operand by one. Ex: DEC B

• MUL AB

• DIV AB

Multiplication A*B Result

8 byte * 8 byte A=low byte,B=high byte

Division

A/BQuotient Remainder

8 byte /8 byte A B

Multiplication of NumbersMUL AB ; A × B, place 16-bit result in B and A

A=07 , B=02 MUL AB ;07 * 02 = 000E where B = 00 and A = 0E

Division of NumbersDIV AB ; A / B , 8-bit Quotient result in A &

8-bit Remainder result in BA=07 , B=02 DIV AB ;07 / 02 = Quotient 03(A) Remainder 01 (B)

2. Logical instructions

•ANL D,S-Performs logical AND of destination & source

- Eg: ANL A,#0FH ANL A,R5•ORL D,S

-Performs logical OR of destination & source- Eg: ORL A,#28H ORL A,@R0

•XRL D,S-Performs logical XOR of destination & source- Eg: XRL A,#28H XRL A,@R0

• CPL A-Compliment accumulator-gives 1’s compliment of accumulator data

• RL A-Rotate data of accumulator towards left without carry

• RLC A- Rotate data of accumulator towards left with carry

• RR A-Rotate data of accumulator towards right without carry

• RRC A- Rotate data of accumulator towards right with carry

3. Data Transfer Instructions

MOV Instruction• MOV destination, source ; copy source to destination.

• MOV A,#55H ;load value 55H into reg. AMOV R0,A ;copy contents of A into R0

;(now A=R0=55H)MOV R1,A ;copy contents of A into R1

;(now A=R0=R1=55H)MOV R2,A ;copy contents of A into R2

;(now A=R0=R1=R2=55H)MOV R3,#95H ;load value 95H into R3

;(now R3=95H)MOV A,R3 ;copy contents of R3 into A

;now A=R3=95H

•MOVX– Data transfer between the accumulator and

a byte from external data memory.•MOVX A, @DPTR•MOVX @DPTR, A

•PUSH / POP– Push and Pop a data byte onto the stack.

•PUSH DPL•POP 40H

• XCH– Exchange accumulator and a byte variable

•XCH A, Rn•XCH A, direct•XCH A, @Ri

4.Boolean variable instructions

CLR:• The operation clears the specified bit indicated in

the instruction• Ex: CLR C clear the carry

SETB:• The operation sets the specified bit to 1.

CPL:• The operation complements the specified bit

indicated in the instruction

•ANL C,<Source-bit>

-Performs AND bit addressed with the carry bit.- Eg: ANL C,P2.7 AND carry flag with bit 7 of P2

•ORL C,<Source-bit>

-Performs OR bit addressed with the carry bit.- Eg: ORL C,P2.1 OR carry flag with bit 1 of P2

• XORL C,<Source-bit>

-Performs XOR bit addressed with the carry bit.- Eg: XOL C,P2.1 OR carry flag with bit 1 of P2

•MOV P2.3,C•MOV C,P3.3•MOV P2.0,C

5. Branching instructions

Jump Instructions• LJMP (long jump):

– Original 8051 has only 4KB on-chip ROM

• SJMP (short jump):– 1-byte relative address: -128 to +127

Call Instructions• LCALL (long call):

– Target address within 64K-byte range

• ACALL (absolute call): – Target address within 2K-byte range

• 2 forms for the return instruction:– Return from subroutine – RET– Return from ISR – RETI

8051 Addressing

8051 Addressing Modes

• The CPU can access data in various ways, which are called addressing modes

1. Immediate2. Register3. Direct4. Indirect5. Relative6. Absolute7. Long8. Indexed

1. Immediate Addressing Mode• The immediate data sign, “#”• Data is provided as a part of instruction.

2. Register Addressing Mode• In the Register Addressing mode, the instruction involves

transfer of information between registers.

3. Direct Addressing Mode

• This mode allows you to specify the operand by giving its actual memory address

4. Indirect Addressing Mode

• A register is used as a pointer to the data.• Only register R0 and R1 are used for this purpose.• R2 – R7 cannot be used to hold the address of an

operand located in RAM.• When R0 and R1 hold the addresses of RAM locations,

they must be preceded by the “@” sign.

MOVX A,@DPTR

5. Relative Addressing

• This mode of addressing is used with some type of jump instructions, like SJMP (short jump) and conditional jumps like JNZ

Loop : DEC A ;Decrement AJNZ Loop ;If A is not zero, Loop

6. Absolute Addressing

• In Absolute Addressing mode, the absoluteaddress, to which the control is transferred, isspecified by a label.

• Two instructions associated with this modeof addressing are ACALL and AJMPinstructions.

• These are 2-byte instructions

7. Long Addressing

• This mode of addressing is used with the LCALL and LJMP instructions.

• It is a 3-byte instruction• It allows use of the full 64K code space.

8. Indexed Addressing

• The Indexed addressing is useful when there is a need to retrieve data from a look-up table (LUT).

8051 Assembly Language

Programming(ALP)

ADDITION OF TWO 8 bit Numbers

ADDRESS LABEL MNEMONICS

9100: MOV A,#05

MOV B,#03

ADD A,B

MOV DPTR,#9200

MOVX @DPTR,AHERE SJMP HERE

559After execution: A=08

SUBTRACTION OF TWO 8 bit Numbers

ADDRESS LABEL MNEMONICS

9100: CLR C

MOV A,#05

MOV B,#03

SUBB A,B

MOV DPTR,#9200

MOVX @DPTR,AHERE SJMP HERE

After execution: A=02

MULTIPLICATION OF TWO 8 bit Numbers

Address Label Mnemonics

9000 START MOV A,#05

MOV B,#03

MUL AB

MOV DPTR,#9200

MOVX @ DPTR,A

INC DPTR

MOV A,B

MOVX @DPTR,A

HERE SJMP HERE

Address Label Mnemonics

9000 START MOV A,#05

MOV B,#03

DIV AB

MOV DPTR,#9200

MOVX @ DPTR,A

INC DPTR

MOV A,B

MOVX @DPTR,A

HERE SJMP HERE

DIVISION OF TWO 8 bit Numbers

After execution: A=0F , B=00 After execution: A=01 , B=02

MOV 40H, #02H store 1st number in location 40HMOV 41H, #04H

MOV 42H, #06H

MOV 43H, #08H

MOV 44H, #01H

MOV R0, #40H store 1 st number address 40H in R0MOV R5, #05H store the count {N=05} in R5MOV B,R5 store the count {N=05} in BCLR A Clear Acc

LOOP: ADD A,@R0INC R0DJNZ R5,LOOPDIV ABMOV 55H,A Save the quotient in location 55H

HERE SJMP HERE

Average of N (N=5) 8 bit Numbers

Answer: 02+04+06+08+01 = 21(decimal) = 15 (Hexa)

SUM = 15 H Average = 21(decimal) / 5 = 04 (remainder) , 01 (quotient) quotient55

Regulation : 2013

UNIT 5 Syllabus

• Programming 8051 Timers • Serial Port Programming • Interrupts Programming • LCD & Keyboard Interfacing • ADC, DAC & Sensor Interfacing • External Memory Interface• Stepper Motor

8051 TIMERS

8051 Timer Modes

Timer 0

Mode 3

Mode 2

Mode 1

Mode 0

Mode 2

Mode 1

Mode 0

Timer 1

8051 TIMERS

TMOD Register

GATE:When set, timer/counter x is enabled, if INTx pin is high and TRx is set. When cleared, timer/counter x is enabled, if TRx bit set.

C/T*:When set(1), counter operation (input from Tx input pin).When clear(0), timer operation (input from internal clock).

TMOD Register

The TMOD byte is not bit addressable.

00- MODE 001- MODE 110- MODE 211- MODE 3

TCON Register

TF 1-Timer 1 overflow flagTF0-TR1- Timer 1 Run control bitTR0-IE1- Interrupt 1IE0-IT1- Timer 1 interruptIT0-

8051 Timer/Counter

OSC ÷12

TLx(8 Bit)

/ 0C T =

/ 1C T =

INT PIN

THx(8 Bit)

TFx(1 Bit)

INTERRUPT

OSC ÷12

TL0/ 0C T =

/ 1C T =

0INT PIN

0TR0T PIN

INTERRUPT

TIMER 0

TL0(5 Bit)

INTERRUPT

TIMER 0 – Mode 0

OSC ÷12/ 0C T =

/ 1C T =

0INT PIN

0TR0T PIN

TH0(8 Bit) TF0

13 Bit Timer / Counter

Maximum Count = 1FFFh (0001111111111111)

TL0(8 Bit)

INTERRUPT

TIMER 0 – Mode 1

OSC ÷12/ 0C T =

/ 1C T =

0INT PIN

0TR0T PIN

TH0(8 Bit) TF0

Maximum Count = FFFFh (1111111111111111)

TH0(8 Bit)

Reload

TIMER 0 – Mode 2

8 Bit Timer / Counter with AUTORELOAD

TL0(8 Bit)

OSC ÷12/ 0C T =

/ 1C T =

0INT PIN

0TR0T PIN

TH0(8 Bit) TF0 INTERRUPT

Maximum Count = FFh (11111111)574

TL0(8 Bit)

INTERRUPT

TIMER 0 – Mode 3

OSC ÷12/ 0C T =

/ 1C T =

0INT PIN

0TR0T PIN

Two - 8 Bit Timer / Counter

OSC ÷12

TH0(8 Bit)

INTERRUPTTF1

OSC ÷12

TL1/ 0C T =

/ 1C T =

INTERRUPT

TIMER 1

1INT PIN

1T PIN

TL1(5 Bit)

INTERRUPT

TIMER 1 – Mode 0

OSC ÷12/ 0C T =

/ 1C T =

TH1(8 Bit) TF1

Maximum Count = 1FFFh (0001111111111111)

1INT PIN

1T PIN

TL1(8 Bit)

INTERRUPT

TIMER 1 – Mode 1

OSC ÷12/ 0C T =

/ 1C T =

TH1(8 Bit) TF1

Maximum Count = FFFFh (1111111111111111)

1INT PIN

1T PIN

TH1(8 Bit)

Reload

TIMER 1 – Mode 2

8 Bit Timer / Counter with AUTORELOAD

TL1(8 Bit)

OSC ÷12/ 0C T =

/ 1C T =

TH1(8 Bit) TF1 INTERRUPT

Maximum Count = FFh (11111111)

1INT PIN

1T PIN

Timer modes

TCON Register (1/2)• Timer control register: TMOD

– Upper nibble for timer/counter, lower nibble for interrupts

• TR (run control bit)– TR0 for Timer/counter 0; TR1 for Timer/counter 1.– TR is set by programmer to turn timer/counter on/off.

• TR=0: off (stop) TR=1: on (start)

TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0Timer 1 Timer0 for Interrupt

(MSB) (LSB)

TCON Register (2/2)

• TF (timer flag, control flag) – TF0 for timer/counter 0; TF1 for timer/counter 1.– TF is like a carry. Originally, TF=0. When TH-TL roll

over to 0000 from FFFFH, the TF is set to 1.• TF=0 : not reach • TF=1: reach • If we enable interrupt, TF=1 will trigger ISR.

TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0Timer 1 Timer0 for Interrupt

(MSB) (LSB)

Equivalent Instructions for the Timer Control Register

For timer 0SETB TR0 = SETB TCON.4CLR TR0 = CLR TCON.4

SETB TF0 = SETB TCON.5CLR TF0 = CLR TCON.5

For timer 1SETB TR1 = SETB TCON.6CLR TR1 = CLR TCON.6

SETB TF1 = SETB TCON.7CLR TF1 = CLR TCON.7

TF1 IT0IE0IT1IE1TR0TF0TR1

TCON: Timer/Counter Control Register

Programs in 8051 TIMERS

Timer Mode 1• In following, we all use timer 0 as an example.

• 16-bit timer (TH0 and TL0)

• TH0-TL0 is incremented continuously when TR0 is set to 1. And the 8051 stops to increment TH0-TL0 when TR0 is cleared.

• The timer works with the internal system clock. In other words, the timer counts up each machine cycle.

• When the timer (TH0-TL0) reaches its maximum of FFFFH, it rolls over to 0000, and TF0 is raised.

• Programmer should check TF0 and stop the timer 0.

Steps of Mode 1 (1/3)

1. Choose mode 1 timer 0– MOV TMOD,#01H

2. Set the original value to TH0 and TL0.– MOV TH0,#FFH– MOV TL0,#FCH

3. You had better to clear the flag to monitor: TF0=0.– CLR TF0

4. Start the timer.– SETB TR0

Steps of Mode 1 (2/3)5.The 8051 starts to count up by incrementing the

TH0-TL0.– TH0-TL0=

FFFCH,FFFDH,FFFEH,FFFFH,0000H

FFFC FFFD FFFE FFFF 0000

TF = 0 TF = 0 TF = 0 TF = 0 TF = 1

TH0 TL0Start timer Stop timer

Monitor TF until TF=1

TR0=1 TR0=0

Steps of Mode 1 (3/3)6. When TH0-TL0 rolls over from FFFFH to

0000, the 8051 set TF0=1. TH0-TL0= FFFEH, FFFFH, 0000H (Now TF0=1)

7. Keep monitoring the timer flag (TF) to see if it is raised.AGAIN: JNB TF0, AGAIN

8. Clear TR0 to stop the process.CLR TR0

9. Clear the TF flag for the next round.CLR TF0

Mode 1 Programming

XTALoscillator ÷ 12

TH TL TF

Timeroverflow

C/T = 0

TF goes high when FFFF 0

Timer Delay Calculation for XTAL = 11.0592 MHz

(a) in hex• (FFFF – YYXX + 1) × 1.085 µs• 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 µs

Example 1 (1/3)• square wave of 50% duty on P1.5 • Timer 0 is used

;each loop is a half clockMOV TMOD,#01 ;Timer 0,mode 1(16-bit)

HERE: MOV TL0,#0F2H ;Timer value = FFF2HMOV TH0,#0FFH CPL P1.5 ACALL DELAY SJMP HERE

50% 50%

whole clock

Example 1 (2/3);generate delay using timer 0DELAY:

SETB TR0 ;start the timer 0AGAIN:JNB TF0,AGAIN

CLR TR0 ;stop timer 0CLR TF0 ;clear timer 0 flagRET

FFF2 FFF3 FFF4 FFFF 0000

TF0 = 0 TF0 = 0 TF0 = 0 TF0 = 0 TF0 = 1

Example 1 (3/3)Solution:In the above program notice the following steps.1. TMOD = 0000 0001 is loaded.2. FFF2H is loaded into TH0 – TL0.3. P1.5 is toggled for the high and low portions of the pulse.4. The DELAY subroutine using the timer is called.5. In the DELAY subroutine, timer 0 is started by the “SETB TR0”

instruction.6. Timer 0 counts up with the passing of each clock, which is provided by the

crystal oscillator. As the timer counts up, it goes through the states of FFF3, FFF4, FFF5, FFF6,

FFF7, FFF8, FFF9, FFFA, FFFB, FFFC, FFFFD, FFFE, FFFFH. One more clock rolls it to 0, raising the timer flag (TF0 = 1). At that point, the JNB instruction falls through.

7. Timer 0 is stopped by the instruction “CLR TR0”. The DELAY subroutine ends, and the process is repeated.

Notice that to repeat the process, we must reload the TL and TH registers, and start the timer again (in the main program).

Example 2 (1/2)• This program generates a square wave on pin P1.5 Using timer 1 • Find the frequency.(dont include the overhead of instruction delay)• XTAL = 11.0592 MHz

MOV TMOD,#10H ;timer 1, mode 1AGAIN:MOV TL1,#34H ;timer value=3476H

MOV TH1,#76H SETB TR1 ;start

BACK: JNB TF1,BACK CLR TR1 ;stopCPL P1.5 ;next half clockCLR TF1 ;clear timer flag 1SJMP AGAIN ;reload timer1

Example 2 (2/2)

Solution:FFFFH – 7634H + 1 = 89CCH = 35276 clock

count Half period = 35276 × 1.085 µs = 38.274 ms Whole period = 2 × 38.274 ms = 76.548 msFrequency = 1/ 76.548 ms = 13.064 Hz.

NoteMode 1 is not auto reload then the program must reload the TH1, TL1 register every timer overflow if we want to have a continuous wave.

Find Timer Values

• Assume that XTAL = 11.0592 MHz .• And we know desired delay• how to find the values for the TH,TL ?

1. Divide the delay by 1.085 µs and get n.2. Perform 65536 –n3. Convert the result of Step 2 to hex (yyxx )4. Set TH = yy and TL = xx.

Example 3 (1/2)• Assuming XTAL = 11.0592 MHz, • write a program to generate a square wave of 50 Hz

frequency on pin P2.3.

Solution:1. The period of the square wave = 1 / 50 Hz = 20 ms.2. The high or low portion of the square wave = 10 ms.3. 10 ms / 1.085 µs = 92164. 65536 – 9216 = 56320 in decimal = DC00H in hex.5. TL1 = 00H and TH1 = DCH.

Example 3 (2/2)

MOV TMOD,#10H ;timer 1, mode 1AGAIN: MOV TL1,#00 ;Timer value = DC00H

MOV TH1,#0DCH SETB TR1 ;start

BACK: JNB TF1,BACK CLR TR1 ;stopCPL P2.3 CLR TF1 ;clear timer flag 1SJMP AGAIN ;reload timer since

;mode 1 is not;auto-reload

Programs in 8051 TIMERS

Another Explanation

MODE 1 Programming{16 bit mode}

MODE 2 Programming{8 bit mode}

Auto Reload Mode

8051 Serial Port

Basics of Serial Communication

• Serial data communication uses two methods– Synchronous method transfers a block of data at a time

– Asynchronous method transfers a single byte at a time

• There are special IC’s made by many manufacturers for serial communications.– UART (universal asynchronous Receiver transmitter)

– USART (universal synchronous-asynchronous Receiver-transmitter)

Asynchronous – Start & Stop Bit

• Asynchronous serial data communication is widely used for character-oriented transmissions

• The start bit is always a 0 (low) and the stop bit(s) is 1 (high)

Asynchronous – Start & Stop Bit

Data Transfer Rate• The rate of data transfer in serial data communication is

stated in bps (bits per second).

• Another widely used terminology for bps is baud rate.– It is modem terminology and is defined as the number of

signal changes per second

8051 Serial Port

• Synchronous and Asynchronous• SCON Register is used to Control• Data Transfer through TXd & RXd pins• Some time - Clock through TXd Pin• Four Modes of Operation:

Mode 0 :Synchronous Serial CommunicationMode 1 :8-Bit UART with Timer Data RateMode 2 :9-Bit UART with Set Data RateMode 3 :9-Bit UART with Timer Data Rate

Registers related to Serial Communication

1. SBUF Register

2. SCON Register

3. PCON Register

SBUF Register

• SBUF is an 8-bit register used solely for serial communication.

• For a byte data to be transferred via the TxD line, it must beplaced in the SBUF register.

• SBUF holds the byte of data when it is received by 8051 RxDline.

SBUF Register

• Sample Program:

SCON Register

SM0 SM1 SM2 REN TB8 RB8 TI RI

Enable MultiprocessorCommunication Mode

Set to EnableSerial Data reception

9th Data Bit Transmittedin Mode 2,3

9th Data Bit Received in Mode 2,3

Set when Stop bit Txed

Set when a Cha-ractor received

8051 Serial Port – Mode 0

The Serial Port in Mode-0 has the following features:

1. Serial data enters and exits through RXD

2. TXD outputs the clock

3. 8 bits are transmitted / received

4. The baud rate is fixed at (1/12) of the oscillator frequency

1. Serial data enters through RXD

2. Serial data exits through TXD

3. On receive, the stop bit goes into RB8 in SCON

4. 10 bits are transmitted / received1. Start bit (0)

2. Data bits (8)

3. Stop Bit (1)

5. Baud rate is determined by the Timer 1 over flow rate.

1. Serial data enters through RXD2. Serial data exits through TXD3. 9th data bit (TB8) can be assign value 0 or 14. On receive, the 9th data bit goes into RB8 in SCON5. 11 bits are transmitted / received

1.Start bit (0)2.Data bits (9)3.Stop Bit (1)

6. Baud rate is programmable

1. Serial data enters through RXD2. Serial data exits through TXD3. 9th data bit (TB8) can be assign value 0 or 14. On receive, the 9th data bit goes into RB8 in SCON5. 11 bits are transmitted / received

1.Start bit (0)2.Data bits (9)3.Stop Bit (1)

6. Baud rate is determined by Timer 1 overflow rate.

Programs in 8051 serial port

TIMER 1 MODE 2 {AUTO RELOAD}

MOV TMOD, #20H ; Timer 1, mode 2MOV TH1,#-06 TH1 is loaded to set the baud rate. MOV SCON, #50HSETB TR1 ; Run Timer 1

L2 : MOV SBUF, # ’A’ Loop: JNB TI, Loop ; Monitor RI

MOV A, SBUFCLR TISJMP L2

Write a program for the 8051 to transfer letter ‘A’ serially at 4800 baud rate, continuously.

MOV TMOD, #20H ; Timer 1, mode 2MOV TH1,#-06 TH1 is loaded to set the baud rate. MOV SCON, #50HSETB TR1 ; Run Timer 1

Loop: JNB RI, Loop ; Monitor RIMOV A, SBUFCLR RISJMP Loop

Program the 8051 to receive bytes of data serially, and put them in P1. Set the baud rate at 4800.

Write a program to transfer the message “YES” serially at 9600 baud, 8 -bit data, 1 stop bit. Do this continuously.

8051 Interrupts

INTERRUPTS

• An interrupt is an external or internal event thatinterrupts the microcontroller to inform it that a deviceneeds its service

• A single microcontroller can serve several devices by twoways:

1. Interrupt2. Polling

Interrupt

– Upon receiving an interrupt signal, themicrocontroller interrupts whatever it is doingand serves the device.

– The program which is associated with theinterrupt is called the interrupt service routine(ISR) .

Interrupt Vs Polling

1. InterruptsWhenever any device needs its service, the device notifies the

microcontroller by sending it an interrupt signal.Upon receiving an interrupt signal, the microcontroller interrupts

whatever it is doing and serves the device.The program which is associated with the interrupt is called the

interrupt service routine (ISR) or interrupt handler.

2. PollingThe microcontroller continuously monitors the status of a given

device.When the conditions met, it performs the service.After that, it moves on to monitor the next device until every one

is serviced.

Steps in Executing an Interrupt1. It finishes the instruction it is executing and saves the address of

the next instruction (PC) on the stack.

2. It also saves the current status of all the interrupts internally (i.e:not on the stack).

3. It jumps to a fixed location in memory, called the interruptvector table, that holds the address of the ISR.

4. The microcontroller gets the address of the ISR from theinterrupt vector table and jumps to it.

5. It starts to execute the interrupt service subroutine until itreaches the last instruction of the subroutine which is RETI(return from interrupt).

6. Upon executing the RETI instruction, the microcontroller returnsto the place where it was interrupted.

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 to the place where it was interrupted. Get pop PC from stack

Interrupt Sources• Original 8051 has 6 sources of interrupts

– Reset (RST)– Timer 0 overflow (TF0)– Timer 1 overflow (TF1)– External Interrupt 0 (INT0)– External Interrupt 1 (INT1)– Serial Port events (RI+TI)

{Reception/Transmission of Serial Character}

8051 Interrupt Vectors

8051 Interrupt related Registers• The various registers associated with the use of

interrupts are:

– TCON - Edge and Type bits for External Interrupts 0/1

– SCON - RI and TI interrupt flags for RS232 {SERIALCOMMUNICATION}

– IE - interrupt Enable

– IP - Interrupts priority

Enabling and Disabling an Interrupt

• The register called IE (interrupt enable) that isresponsible for enabling (unmasking) and disabling(masking) the interrupts.

Interrupt Enable (IE) Register

• EA : Global enable/disable.

• --- : Reserved for additional interrupt hardware.

• ES : Enable Serial port interrupt.

• ET1 : Enable Timer 1 control bit.

• EX1 : Enable External 1 interrupt.

• ET0 : Enable Timer 0 control bit.

• EX0 : Enable External 0 interrupt.

MOV IE,#08hor

SETB ET1

Interrupt Priority

Interrupt Priority (IP) Register

PS PT1 PX1 PT0 PX0Reserved

Serial Port

Timer 1 Pin

INT 1 Pin Timer 0 Pin

INT 0 Pin

Priority bit=1 assigns high priorityPriority bit=0 assigns low priority

KEYBOARD INTERFACING

KEYBOARD INTERFACING • Keyboards are organized in a matrix of rows

and columnsThe CPU accesses both rows and columns

through ports .• �Therefore, with two 8-bit ports, an 8 x 8

matrix of keys can be connected to a microprocessor

When a key is pressed, a row and a column make a contact

•Otherwise, there is no connection between rows and columns

•�A 4x4 matrix connected to two portsThe rows are connected to an

output port and the columns are connected to an input port

4x4 matrix

Connection with keyboard matrix

Final Circuit

Stepper Motor Interfacing

• Stepper motor is used in applications such as; dot matrix printer, robotics etc

• It has a permanent magnet rotor called the shaft which is surrounded by a stator. Commonly used stepper motors have 4 stator windings

• Such motors are called as four-phase or unipolar stepper motor.

Full step

Step angle:

• Step angle is defined as the minimum degree of rotation with a single step.

• No of steps per revolution = 360° / step angle• Steps per second = (rpm x steps per revolution) / 60• Example: step angle = 2°• No of steps per revolution = 180

A switch is connected to pin P2.7. Write an ALP to monitor the status of the SW. If SW = 0, motor moves clockwise and If SW = 1, motor moves anticlockwise

SETB P2.7MOV A, #66HMOV P1,A

TURN: JNB P2.7, CWRL AACALL DELAYMOV P1,ASJMP TURN

CW: RR AACALL DELAYMOV P1,ASJMP TURN662

DELAY: MOV R1,#20L2: MOV R2,#50L1:DJNZ R2,L2

DJNZ R2,L1RET

LCD Interfacing using 8051

{before discussed in Unit 3 LCD interfacing using 8086}

Pin Connections of LCD:

A/D Interfacing using 8051

{before discussed in Unit 3 A/D interfacing using 8086}

Refer book Mohammad Ali Explanation is not sufficient

Interfacing ADC to 8051ADC0804 is an 8 bit successive approximation analogue to digital

converter from National semiconductors. The features of ADC0804 are differential analogue voltage inputs, 0-5V input voltage range, no zero adjustment, built in clock generator, reference voltage can be externally adjusted to convert smaller analogue voltage span to 8 bit resolution etc.

ADC Interfacing:

D/A Interfacing using 8051

{before discussed in Unit 3 D/A interfacing using 8086}

8051 Connection to DAC808

program to send data to the DAC to generate a stair-step ramp

SENSOR INTERFACING

take temperature sensor for example

Shunt voltage diodes

potentiometer

EXTERNAL MEMORY

INTERFACING676

Access to External Memory• Port 0 acts as a multiplexed address/data bus. Sending

the low byte of the program counter (PCL) as an address.

• Port 2 sends the program counter high byte (PCH) directly to the external memory.

• The signal ALE operates as in the 8051 to allow an external latch to store the PCL byte while the multiplexed bus is made ready to receive the code byte from the external memory.

• Port 0 then switches function and becomes the data bus receiving the byte from memory.

Documents References• 8086 SYSTEM BUS STRUCTURE by Prof.L.PETER STANLEY

BEBINGTON ( PROFESSOR AND DEAN(ACADEMIC),VCET,Erode)

• I/O Interfacing by Prof.P.JAYACHANDAR , ASSOCIATE PROFESSOR and DEAN(SA),VCET,Erode

• 8086 Microprocessor by Dr. M. Gopikrishna ,Assistant Professor of Physics,Maharajas College ,Ernakulam

• 8086 architecture By Er. Swapnil Kaware• 8086 presentations by Gursharan Singh Tatla (Eazynotes.com)• Microprocessor - Ramesh Gaonkar• 8086 micro processor prasadpawaskar• 8086 class notes-Y.N.M by MURTHY Y.N• Introduction to 8086 Microprocessor by Rajvir Singh• 8086 micro processor by Poojith Chowdhary• 8086 ASSEMBLY LANGUAGE PROGRAMMING Cutajar & Cutajar• Intel microprocessor history by Ramzi_Alqrainy

Website References• http://80864beginner.com/• www.eazynotes.com• www.slideshare.net• www.scribd.com• www.docstoc.com• www.slideworld.com• www.nptel.ac.in• http://opencourses.emu.edu.tr/• http://engineeringppt.blogspot.in/• http://www.pptsearchengine.net/• www.4shared.com• http://8085projects.info/

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