Download ppt - Orientation of Subject By:- Mr.G.P SINGH Asst.Prof. Faculty of Computer Application,Gharaun Campus,Mohali 111/10/2013

Orientation of Subject By:-

Mr.G.P SINGH Asst.Prof.

Faculty of Computer Application,Gharaun Campus,Mohali 104/10/23

INTRODUCTION TO MICROPROCESSOR

MCA-205 (N2)

Internal Assessment: 40

External Assessment: 60


CONTENTSSection AIntroduction to Microprocessor, its historical background and Microprocessor applications.

INTEL 8085: Microprocessor Architecture and its operations, 8085 MPU and its architecture, 8085

instruction cycle and timing diagram, Memory read and Memory Write operations, Instructions for

8085: Data movement, Arithmetic and logic; and branch control instructions

Section BINTEL 8086: Introduction, 8086Architecture, real and Protected mode, Memory Addressing,

Memory Paging, Addressing Modes. Pin diagram of 8086, clock generator (8284A)

Section CVarious types of instructions: Data movement, Arithmetic and logic; and program control.

Section DInterrupts: Introduction, 8257 Interrupt controller, basic DMA operation and 8237 DMA Controller,

Arithmetic coprocessor, 80X87 Architecture, ., RISC v/s CISC

processors.


REFERENCES:

• B. Brey The Intel microprocessors 8086/8086, 80186/80188, 80286,80386, 80486 Pentium pro processor Architecture,Programming and interfacing 4th Edition.

• B. Ram Fundamentals of microprocessors and HI microcomputers,Dhanpat RaiPublication.

• Ramesh S. Gaonkar Microprocessor Architecture, Programming and Applications with 8085,4th edition, Penram International Publishing (India)


Practical Hardware Lab – I(Microprocessor)MCA-207 (N2)

Internal Assessment 40External Assessment 60

• Using 8085 and 8086 microprocessor kits do the following programs:• 8085• 1. To examine and modify the contents of a register and memory location.• 2. To add two hexadecimal nos.• 3. To subtract two hexadecimal nos.• 4. To add two hexadecimal nos. The result should not be greater than 199.• 5. To add two sixteen bit nos.• 6. To subtract two sixteen bit nos.• 7. For addition of 8 bit no series neglecting the carry generated.• 8. To separate hexadecimal number into two digits(Breaking the byte into two nibbles).• 8086• 1.To add two binary no’s each 8 bit long.• 2 To add two binary no’s each 8 bit long.• 3. To multiply two binary no’s.• 4.To find the maximum no in a given string (16 bytes long) and store it in a• particular location.• 5.To find the minimum no in a given string (16 bytes long) and store it in a• particular location.• 6.To sort a string of a no of bytes in descending order.• 7.To multiply an ASCII string of eight numbers by single ASCII digit.• 8.To calculate the no. of bytes in a string starting from a particular location up to an Identifier• (data byte) placed in AL register. Store the actual count in a particular memory• Location.


What we’ll Study in This?Theory-Part

• 1. Microprocessor’s Origin.• 2. Various Processor’s available till date.• 3. Application in real world.i.e daily life

examples.(Case Studies )…Traffic light,etc.4. Programming in ALP(in Practical using 8085 and 8086 Kit.)

• 5. Job Prospects???????????????


Practical Part

1. Programming in ALP(using 8085 and 8086 Kit.)


INTRODUCTION

• COMPUTER GENERATIONS:-• First Generation Computers(1940-1956) • VACUUM TUBES .e.g.:-ENIAC(Electronic Numerical Integrator

and Calculator)• EDVAC:-Electronic discrete Variable Automatic Computer.• EDSAC: Electronic Delay Storage Automatic Computer.• UNIVAC-1: Universal Accounting Computer Setup.


COMPUTER GENERATIONS

• Second Generation(1956-1963)• Transistors.e.g IBM 1620,IBM 1401,CDC

3600• Programming Languages:-

COBOL,FORTAN.



• THIRD GENERATION(1964-1971)• INTEGRATED CIRCUITS:-(CHIPS),

(Registers,capacitors,Transistors)• IBM-360,ICL-1900,IBM-370,VAX-750.• Programming Language:- BASIC



• FOURH GENERATION(1971-Present)• MICROPROCESSORS.• LSIC(Large Scale Integrated Circuits) built on

single Chip called as MICROPROCESSORS.• VLSIC(Very Large scale integrated Circuits)• E.g.:- PC.



• FIFTH GENERATION:-PRESENT and BEYOND• ARTIFICIAL INTELLIGENCE.• YEAR-1990-Fifth Generation Computers

Started.• QUANTUM COMPUTATION,MOLECULAR,NANOTECHNOLOGY.• Goal:- To develop computer that respond to natural language

input and are capable of learning and self-organization.


HISTORY OF MICROPROCESSORS

• Fairchild Semiconductors (founded in 1957) invented the first IC in

1959.

• In 1968, Robert Noyce, Gordan Moore, Andrew Grove resigned from

Fairchild Semiconductors

• They founded their own company Intel (Integrated Electronics).

• Intel grown from 3 man start-up in 1968 to industrial giant by 1981.

• It had 20,000 employees and $188 million revenue.


Generation of Microprocessor

• FIRST GENERATION MICROPROCESSOR:-• Ted Hoff of INTEL Corporation developed

Controlled Processor in 1969.• Intel 4004:-• Introduced in 1971.

• It was the first microprocessor by Intel

• It was a 4-bit MP.

• PMOS Technology.

• Device: CALCULATOR



• Intel 4040:-

• Introduced in 1971.

• It was also 4-bit MP.



Faculty of Computer Application,Gharaun Campus,Mohali

•INTEL-8008

•Introduced in 1972.

•It was first 8-bit MP.

•Could execute 50,000

instructions per second

1604/10/23

Generation of MicroprocessorFirst Generation Summary

MICRPPROCESSOR WORD SIZE

INTEL 4004 & 4040 4-bit

FAIRCHILD PPS-25 4-bit

NATIONAL IMP-4 4-bit

ROCKWELL PPS-4 4 bit

MICROSYSTEM 4-bit

INYEL 8008 8-bit

NATIONAL IMP-8 8-bit

ROCKWELL PPS 8-bit

AMI 7200 8-bit

MOSTEK 5065 8-bit


Generation of Microprocessor2nd Generation

• Started in Year-1973.• Intel 8080• It was also 8-bit MP.

• Was 10 times faster than 8008.

• Could execute 5,00,000 instructions per second

• NMOS TECHNOLOGY.




Introduced in 1977.

It was also 8-bit MP.

Could execute 7,69,230 instructions

per second.

It could access 64 KB of memory.

It had 256 instructions.

Over 100 million copies were sold

Intel 8085

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• FEATURES OF SECOND GENERATION:-• LARGE CHIP SIZE(170*200) WITH 40 PINS.• MORE CHIP ON DECODING CIRCUITS.• ABLITY TO ADDRESS LARGE MEMORY SPACE(64KB) AND I/O PORTS

(256).• MORE POWERFUL INSTRUCTION SET.• Dissipate less power.• Better INTERUPT HANDLING FACILITIES. • CYCLE TIME REDUCED TO HALF (1.3 TO 9 n.s)• LESS SUPPORT CHIPS REQUIRED.• USED SINGLE POWER SUPPLY.



Second Generation Summary

MICROPROCESSOR WORD SIZE

INTEL 8080/8085 8-bit

FAIRCHILD F8 8-bit

NATIONAL CMP-4 8 bit

MOTOROLA 6800 8 bit

RCA COSMAC 8 bit

MOS TECH 6500 8 bit

SIGNETICS 2650 8 bit

ZILOG Z-80 8 bit

INTERSIL 6100 12 bit

TOSHIBA TICS-12 12 bit


Generation of Microprocessor3rd Generation

• Intel 8086• Introduced in 1978.

• It was first 16-bit MP.

• Could execute 2.5 million instructions /sec.

• It could access 1 MB of memory.

• It had 22,000 instructions.

• It had Multiply and Divide instructions.

• HMOS TECHNOLOGY.(high density short channel MOS)



• Intel 8088



• Could execute 2.5 million instructions per second.

• It could access 1 MB of memory.

• It had 22,000 instructions.

• It had Multiply and Divide instructions




•Introduced in 1982.

•They were 16-bit MPs.

•They had additional components like:

•Interrupt Controller

•Clock Generator

•Local Bus Controller

•Counters

Intel 80186 & 80188

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Generation of Microprocessor4th Generation

• Intel 80286 Introduced in 1982.

It was 16-bit MP.

It could address 16 MB of memory.

It could execute 4 million instructions per second.

Its clock speed was 8 MHz



• Intel 80386• Introduced in 1986.

• It was first 32-bit MP.

• It could address 4 GB of memory.

• Different versions:

• 80386 SX

• 80386 SL / 80386 SLC

• 80386 EX





• It had 1.2 million transistors.

• Cache memory was introduced


Intel 80486

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Generation of Microprocessor5th Generation(1993-onwards)

• Intel Pentium• Introduced in March 22,1993.


• It was originally named 80586.

• Could execute 110 million instructions per sec.

• Cache memory:

• 8 KB for instructions.

• 8 KB for data


Generation of MicroprocessorTHE PENTIUM PRO

• Intel Pentium Pro• Introduced in 1995.


• It had 21 million transistors

• Cache memory:

• 8 KB for instructions.

• 8 KB for data.

• It had L2 cache of 256 KB.(Level 2)• L2 cache memory, also called the secondary cache, resides on a separate chip from the microprocessor chip


http://www.webopedia.com/TERM/C/chip.htm

Generation of MicroprocessorTHE PENTIUM SERIES

• Intel Pentium II• Introduced in 1997.


• Could execute 333 million instructions per second.

• MMX technology was supported.(Multi-Media-eXtension)

• L2 cache & processor were on one circuit.

• Level 3 cache is now the name for the extra cache built into

motherboards between the microprocessor and the main memory.Faculty of Computer Application,Gharaun

Campus,Mohali 3004/10/23

http://www.webopedia.com/TERM/C/cache.htm

http://www.webopedia.com/TERM/M/motherboard.htm

http://www.webopedia.com/TERM/M/main_memory.htm


• Intel Pentium II Xeon• Introduced in 1998.


• It was designed for servers.

• L1 cache of 32 KB & L2 cache of 512 KB, 1MB or 2 MB.

• It could work with 4 Xeons in same system.



• Intel Pentium III



• Its clock speed was 1GHz.



• Intel Pentium IV• Introduced in 2000.


• L1 cache was of 32 KB & L2 cache of 256 KB.

• It had 42 million transistors.

• All internal connections were made from aluminum to copper



• Intel Dual Core• Introduced in 2006.

• It was 32-bit or 64-bit MP.

• It had two cores.

• It supported SMT technology.

• SMT: Simultaneously Multi-Threading

• E.g.: Adobe Photoshop supported SMT



• Intel Core 2 Duo


• It was 32-bit or 64-bit MP


The Intel family of Processors

• Intel was founded on July 18, 1968, as Integrated Electronics Corporation, is based in Santa Clara, California, USA.

• Gordon Moore and Robert Noyce


http://en.wikipedia.org/wiki/Santa_Clara,_California

http://en.wikipedia.org/wiki/California

OTHER PROCESSOR’S

• Elbrus E2K(Elbrus 2000):-• It has been developed by МЦСТ (MZST, Moscow

center for SPARC-technology).• Elbrus:- ExpLicit Basic Resources Utilization

Scheduling.(named after Mount Elbrus in russia)• Soviet supercomputer systems developed by

Lebedev Institute of Precision Mechanics and Computer Engineering


http://en.wikipedia.org/w/index.php?title=%D0%9C%D0%A6%D0%A1%D0%A2&action=edit&redlink=1

http://en.wikipedia.org/wiki/Mount_Elbrus

http://en.wikipedia.org/wiki/Soviet_Union

• Advanced Micro Devices, Inc. (AMD)• It is an American multinational semiconductor company based in

Sunnyvale, California USA.

• products include microprocessors, motherboard chipsets, embedded processors and graphics processors for servers, workstations and personal computers, and processor technologies for handheld devices, digital television, automobiles, game consoles, and other

embedded systems applications.


List of AMD microprocessors


AMD AM9080ADC / C8080A), 1977

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AMD D8086

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AMD K51996

4104/10/23



K6 (Model 6)1997.

4204/10/23



K6 "Little Foot" (Model 7)

4304/10/23



Athlon (Thunderbird (T-Bird)

June 5, 2000

4404/10/23



Athlon XP/MP Palomino

October 9, 2001

4504/10/23



Thoroughbred (T-Bred)

10 June 2002

4604/10/23



AMD Duron "Spitfire" 600MHz CPU

June 19, 2000

4704/10/23



Sempron 3000+ (Barton)

July 2004

4804/10/23

APPLICATIONS OF MICROPROCESSOR

1. Microprocessors used in everything from the smallest embedded systems and handheld devices to the largest mainframes and supercomputers.

2. Embedded system:- An embedded system is a computer system designed to perform one or a few dedicated functions often with real-time computing constraints. It is embedded as part of a complete device often including hardware and mechanical parts. By contrast, a general-purpose computer, such as a personal computer (PC), is designed to be flexible and to meet a wide range of end-user needs. Embedded systems control many devices in common use today.

Embedded systems are controlled by one or more main processing cores that are typically either microcontrollers or digital signal processors (DSP).The key characteristic, however, is being dedicated to handle a particular task, which may require very powerful processors.



• For example, air traffic control systems may usefully be viewed as embedded, even though they involve mainframe computers and dedicated regional and national networks between airports and radar sites (each radar probably includes one or more embedded systems of its own).



• The embedded system is dedicated to specific tasks, design engineers can optimize it to reduce the size and cost of the product and increase the reliability and performance.

• Embedded systems range from portable devices such as digital watches and MP3 players, to large stationary installations like traffic lights, factory controllers, or the systems controlling nuclear power plants. Complexity varies from low, with a single microcontroller chip, to very high with multiple units, peripherals and networks mounted inside a large chassis or enclosure.



• The Intel Core i7 microprocessor in aerospace and defense applications .

• Today, micro processors are included in almost any electronically device: computers, and any computer-like device such as mobile phones, PDAs, digital video cameras or recorders, digital cameras, etc. Microprocessors are also used in many cars (or: vehicles in general), domestic appliances like washing machines, refrigerators, microwave ovens or coffee makers. Basically, almost any electronic device, or device that uses electronics, employs some form of a micro processor.The group of devices using micro processors even extends to those devices that were traditionally pure electrical, or electro-mechanic, devices such as light switches or light bulb holders, thermostatic radiator valves.

•



• iPhone :- There are actually 2 microprocessors in the iPhone: The processor and the baseband. The baseband controls wireless functions of the iPhone such as Bluetooth and telephone connection. This processor is a resource to the main processor which is used to control the user interface and higher-level systems of the Phone, such as applications that the user is likely to interact with.


Difference between a microprocessor and a microcontroller?

• A microcontroller is a specialized form of microprocessor that is designed to be self-sufficient and cost-effective, where a microprocessor is typically designed to be general purpose (the kind used in a PC). Microcontrollers are frequently found in automobiles, office machines, toys, and appliances.

• The microcontroller is the integration of a number of useful functions into a single IC package. These functions are:

a) The ability to execute a stored set of instructions to carry out user defined tasks. b) The ability to be able to access external memory chips to both read and write data from and to the memory.

Basically, a microcontroller is a device which integrates a number of the components of a microprocessor system onto a single microchip.


Microcontroller combines onto the same microchip.

• The CPU core (microprocessor) .

• Memory (both ROM and RAM) .

• Some parallel digital I/O • Also, a microcontroller is part of an

embedded system, which is essentially the whole circuit board.


BLOCK DIAGRAM OFINTEL 8085


Introduction to 8085• Introduced in 1977.

• It is 8-bit MP.

• It is a 40 pin dual-in-line chip.

• It uses a single +5V supply for its operations.

• Its clock speed is about 3MHz.


Block Diagram of 8085


Three Units of 8085

• Processing Unit

• Instruction Unit

• Storage and Interface Unit


Processing Unit

• Arithmetic and Logic Unit

• Accumulator

• Status Flags

• Temporary Register


Instruction Unit

• Instruction Register

• Instruction Decoder

• Timing and Control Unit


Storage and Interface Unit

• General Purpose Registers

• Stack Pointer

• Program Counter

• Increment/Decrement Register

• Address Latch

• Address/Data Latch


Three Other Units

• Interrupt Controller

• Serial I/O Controller

• Power Supply


Accumulator

• It the main register of microprocessor.

• It is also called register ‘A’.

• It is an 8-bit register.

• It is used in the arithmetic and logic operations.

• It always contains one of the operands on which arithmetic/logic has to be performed.

• After the arithmetic/logic operation, the contents of accumulator are replaced by the result.


Arithmetic & Logic Unit (ALU)• It performs various arithmetic and logic

operations.

• The data is available in accumulator and temporary/general purpose registers.

• Arithmetic Operations:

– Addition, Subtraction, Increment, Decrement etc.

• Logic Operations:

– AND, OR, X-OR, Complement etc.


Temporary Register


• It is used to store temporary 8-bit operand from general purpose register.

• It is also used to store intermediate results.


Status Flags

• Status Flags are set of flip-flops which are used to check the status of Accumulator after the operation is performed.


Status Flags

• S = Sign Flag

• Z = Zero Flag

• AC = Auxiliary Carry Flag

• P = Parity Flag

• CY = Carry Flag


Status Flags

• Sign Flag (S):

– It tells the sign of result stored in Accumulator after the operation is performed.

– MSB(7th bit) of 8 bit number will tell sign. Rest of bit’s will tell magnitude.(same in case of 16 bit or 32 bit).

– So numbers can be used in the range -128 to 127.

– If result is –ve i.e MSB is 1, sign flag is set (1).

– If result is +ve i.e MSB is 0, sign flag is reset (0).


Status Flags

• Zero Flag (Z):– It tells whether the result stored in Accumulator is zero or not after the operation is

performed.

– If result is zero, zero flag is set (1).

– If result is not zero, zero flag is reset (0).

– Hexadecimal: B3+4D=00, Carry:- 1

– SO CARRY FLAG (CY) IS ALSO SET TO 1.


Status Flags

• Auxiliary Carry Flag (AC):– It is used in BCD operations.

– ADD CB+E9=B4.

– There is carry from 3rd bit to 4th bit. So AC is set to 1.

– The counting stars from zero.

– If there is carry in BCD addition, auxiliary carry is set (1).

– If there is no carry, auxiliary carry is reset (0).


Status Flags

• Parity Flag (P):

– It tells the parity of data stored in Accumulator after execution of airthmatic or logical operations..

– It is defined as number of “1’s” present in the accumulator.

– If parity is even, parity flag is set (1).

– If parity is odd, parity flag is reset (0).


Program Status Word (PSW)

• The contents of Accumulator and Status Flags clubbed together is known as Program Status Word (PSW).

• It is a 16-bit word.


Instruction Register

• It is used to hold the current instruction which the microprocessor is about to execute.



Instruction Decoder

• It interprets the instruction stored in instruction register.

• It generates various machine cycles depending upon the instruction.

• The machine cycles are then given to the Timing and Control Unit.


Timing and Control Unit

• It controls all the operations of microprocessor and peripheral devices.

• Depending upon the machine cycles received from Instruction Decoder, it generates 12 control signals:

– S0 and S1 (Status Signals).

– ALE (Address Latch Enable).


Timing and Control Unit– RD (Read, active low).

– WR (Write, active low).

– IO/M (Input-Output/Memory).

– READY

– RESET IN

– RESET OUT

– CLK OUT

– HOLD and HLDA


General Purpose Registers• There are 6 general purpose registers, namely B, C, D, E, H, L.

• Each of the them is 8-bit register.

• They are used to hold data and results.

• To hold 16-bit data, combination of two 8-bit registers can be used.

• This combination is known as Register Pair.

• The valid register pairs are:

– B – C, D – E, H – L.


Program Counter

• It is used to hold the address of next instruction to be executed.

• It is a 16-bit register.

• The microprocessor increments the value of Program Counter after the execution of the current instruction, so that, it always points to the next instruction.


Stack Pointer

• It holds the address of top most item in the stack.

• It is also 16-bit register.

• Any portion of memory can be used as stack.


Increment/Decrement Register

• This register is used to increment or decrement the value of Stack Pointer.

• During PUSH operation, the value of Stack Pointer is incremented.

• During POP operation, the value of Stack Pointer is decremented.


Address Latch

• It is group of 8 buffers.

• The upper-byte of 16-bit address is stored in this latch.

• And then it is made available to the peripheral devices.


Address/Data Latch• The lower-byte of address and 8-bit of data are

multiplexed.

• It holds either lower-byte of address or 8-bits of data.

• This is decided by ALE (Address Latch Enable) signal.

• If ALE = 1 then

– Address/Data Latch contains lower-byte of address.

• If ALE = 0 then

– It contains 8-bit data.


Serial I/O Controller

• It is used to convert serial data into parallel and parallel data into serial.

• Microprocessor works with 8-bit parallel data.

• Serial I/O devices works with serial transfer of data.

• Therefore, this unit is the interface between microprocessor and serial I/O devices.


Interrupt Controller

• It is used to handle the interrupts.

• There are 5 interrupt signals in 8085:

– TRAP

– RST 7.5

– RST 6.5

– RST 5.5

– INTRFaculty of Computer Application,Gharaun


Interrupt Controller

• Interrupt controller receives these interrupts according to their priority and applies them to the microprocessor.

• There is one outgoing signal INTA which is called Interrupt Acknowledge.


Power Supply

• This unit provides +5V power supply to the microprocessor.

• The microprocessor needs +5V power supply for its operation.


How to increase speed of Operation of 8085?

• The main use is to hold data which is Frequently used.

• It increases the speed of program execution. The data in Microprocessor can be stored in memory OR GENERAL PURPOSE registers. If the data is present in memory the mpu has to perform an operation of memory read. This data is taken by microprocessor, The required operation is performed and result is stored back to memory. To store result in memory the microprocessor has to perform one more operation of memory WRITE. So there are two operations involved in using memory to hold data.

• But if data is present in general purpose register there is no operation involved. As the general purpose registers are part of microprocessor architecture, the microprocessor doesn’t have to perform any external memory read and write operation. Thus the time required to execute program using general purpose register is very less as compared to program using memory.


Further Reading of Covered Topic


• Chapter :- 3• Page no:- 3.1 to 3.5


PIN-Diagram of 8085

• Introduction to 8085 It was introduced in 1977. It is 8-bit microprocessor. Its actual name is 8085 A. It is single NMOS device. It contains 6200 transistors approx. Its dimensions are

164 mm x 222 mm. It is having 40 pins Dual-Inline-Package (DIP).


Introduction to 8085

It has three advanced versions:◦8085 AH◦8085 AH2◦8085 AH1

These advanced versions are designed using HMOS technology.



The advanced versions consume 20% less power supply.

The clock frequencies of 8085 are:◦8085 A 3 MHz◦8085 AH 3 MHz◦8085 AH2 5 MHz◦8085 AH1 6 MHz



• The signals are in following groups:-

• Power supply signals

• Clock signals

• Reset signals

• Interrupt signals

• Address and data bus

• Status and control signals

• Serial input/output Signals

• DMA request signals


Pin Diagram of 8085


X1 & X2

Pin 1 and Pin 2 (Input)

Faculty of Computer Application,Gharaun Campus,Mohali 95

These are also called Crystal Input Pins.

Crystal is used as a clock source

8085 can generate clock signals internally.

To generate clock signals internally, 8085 requires external inputs from X1 and X2.

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Crystal

• A crystal oscillator is an electronic oscillator circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a very precise frequency. This frequency is commonly used to keep track of time (as in quartz wristwatches), to provide a stable clock signal for digital integrated circuits, and to stabilize frequencies for radio transmitters and receivers. The most common type of piezoelectric resonator used is the quartz crystal, so oscillator circuits designed around them became known as "crystal oscillators."

04/10/23 Faculty of Computer Application,Gharaun Campus,Mohali 96

X1 & X2

Pin 1 and Pin 2 (Input)

• Intel 8085 needs 3.07 MHz frequency as a clock signal. generally we know that,clock frequency is half of the crystal frequency. so we connect crystal between pin no 1 & 2 in order to make 6.14 MHz frequency accurately. so that we have crystal frequency of 3.07 MHz for Intel 8085 microprocessor.

• Why crystal is a preferred clock source?

• Because of high stability, large Q (Quality Factor) & the frequency that doesn’t drift with aging. Crystal is used as a clock source most of the times.


RESET IN and RESET OUTPin 36 (Input) and Pin 3 (Output)


98

RESET IN:

◦ It is used to reset the microprocessor.

◦ It is active low signal.

◦When the signal on this pin is low for at least 3 clocking cycles, it forces the microprocessor to reset itself.

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Resetting the microprocessor means:

◦Clearing the PC and IR.◦Disabling all interrupts

(except TRAP).◦Disabling the SOD pin.◦All the buses (data,

address, control) are tri-stated.

◦Gives HIGH output to RESET OUT pin.

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RESET OUT:

◦ It is used to reset the peripheral devices and other ICs on the circuit.

◦ It is an output signal.

◦ It is an active high signal.

◦ The output on this pin goes high whenever RESET IN is given low signal.

◦ The output remains high as long as RESET IN is kept low.

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SID and SODPin 4 (Input) and Pin 5 (Output)


SID (Serial Input Data):

o It takes 1 bit input from serial port of 8085.

o Stores the bit at the 8th position (MSB) of the Accumulator.

o RIM (Read Interrupt Mask) instruction is used to transfer the bit.

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SID and SODPin 4 (Input) and Pin 5 (Output)


SOD (Serial Output Data):

o It takes 1 bit from Accumulator to serial port of 8085.

o Takes the bit from the 8th position (MSB) of the Accumulator.

o SIM (Set Interrupt Mask) instruction is used to transfer the bit.

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103

8085 Interrupts

8085

TRAPRST7.5RST6.5RST 5.5

INTRINTA

Faculty of Computer Application,Gharaun Campus,Mohali04/10/23 Faculty of Computer Application,Gharaun Campus,Mohali

Interrupt Pins


Interrupt:

• It means interrupting the normal execution of the microprocessor.

• When microprocessor receives interrupt signal, it discontinues whatever it was executing.

• It starts executing new program indicated by the interrupt signal.

• Interrupt signals are generated by external peripheral devices.

• After execution of the new program, microprocessor goes back to the previous program.

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Sequence of Steps Whenever There is an Interrupt


Microprocessor completes execution of current instruction of the program.

PC contents are stored in stack.

PC is loaded with address of the new program.

After executing the new program, the microprocessor returns back to the previous program.

It goes to the previous program by reading the top value of stack.

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Responding to Interrupts

• Responding to an interrupt may be immediate or delayed depending on whether the interrupt is maskable or non-maskable and whether interrupts are being masked or not.

• There are two ways of redirecting the execution to the ISR depending on whether the interrupt is vectored or non-vectored.

– Vectored: The address of the subroutine is already known to the Microprocessor

– Non Vectored: The device will have to supply the address of the subroutine to the Microprocessor


Five Hardware Interrupts in 8085


TRAP

RST 7.5

RST 6.5

RST 5.5

INTR

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Classification of Interrupts


108

• Maskable and Non-Maskable

• Vectored and Non-Vectored

• Edge Triggered and Level Triggered

• Priority Based Interrupts

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MASKING

• Disabling of interrupt is called MASKING.• When interrupt are to be used they are

enabled by Software using the instruction ENABLE INTERUPT.[EI].The instruction DISABLE INTERRUPT [DI] is used to disable interupts.


Maskable Interrupts


110

• Maskable interrupts are those interrupts which can be enabled or disabled.

• Enabling and Disabling is done by software instructions.

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Maskable Interrupts


111

• List of Maskable Interrupts:

• RST 7.5

• RST 6.5

• RST 5.5

• INTR

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Non-Maskable Interrupts


112

• The interrupts which are always in enabled mode are called non-maskable interrupts.

• These interrupts can never be disabled by any software instruction.

• TRAP is a non-maskable interrupt.

• It is not accessible to user.

• TRAP is usually used for power failure and emergency shutoff.

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Vectored Interrupts


113

• The interrupts which have fixed memory location for transfer of control from normal execution.

• Each vectored interrupt points to the particular location in memory.

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Vectored Interrupts


114

• List of vectored interrupts:

• RST 7.5

• RST 6.5

• RST 5.5

• TRAP

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Vectored Interrupts


The addresses to which program control goes:

Absolute address is calculated by multiplying the RST value with 0008 H.

Name Vectored Address

RST 7.5 003C H (7.5 x 0008 H)

RST 6.5 0034 H (6.5 x 0008 H)

RST 5.5 002C H (5.5 x 0008 H)

TRAP 0024 H (4.5 x 0008 H)

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Non-Vectored Interrupts


116

• The interrupts which don't have fixed memory location for transfer of control from normal execution.

• The address of the memory location is sent along with the interrupt.

• INTR is a non-vectored interrupt.

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Edge Triggered Interrupts


117

• The interrupts which are triggered at leading or trailing edge are called edge triggered interrupts.

• RST 7.5 is an edge triggered interrupt.

• It is triggered during the leading (positive) edge.

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Level Triggered Interrupts


The interrupts which are triggered at high or low level are called level triggered interrupts.

RST 6.5RST 5.5INTR

TRAP is edge and level triggered interrupt.04/10/23

Priority Based Interrupts


119

• Whenever there exists a simultaneous request at two or more pins then the pin with higher priority is selected by the microprocessor.

• Priority is considered only when there are simultaneous requests.

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Priority Based Interrupts


120

• Priority of interrupts:

Interrupt Priority

TRAP 1

RST 7.5 2

RST 6.5 3

RST 5.5 4

INTR 5

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TRAPPin 6 (Input)


121

It is an non-maskable interrupt.It has the highest priority.It cannot be disabled.It is both edge and level

triggered.It means TRAP signal must go

from low to high.And must remain high for a

certain period of time.TRAP is usually used for power

failure and emergency shutoff.

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RST 7.5Pin 7 (Input)


122

It is a maskable interrupt.It has the second highest

priority.It is positive edge

triggered only.The internal flip-flop is

triggered by the rising edge.

The flip-flop remains high until it is cleared by RESET IN.

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It is a maskable interrupt.It has the third highest

priority.It is level triggered only.The pin has to be held

high for a specific period of time.

RST 6.5 can be enabled by EI instruction.

It can be disabled by DI instruction.

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124

It is a maskable interrupt.

It has the fourth highest priority.

It is also level triggered.The pin has to be held

high for a specific period of time.

This interrupt is very similar to RST 6.5.

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INTRPin 10 (Input)


It is a maskable interrupt.It has the lowest priority.It is also level triggered.It is a general purpose

interrupt.By general purpose we

mean that it can be used to vector microprocessor to any specific subroutine having any address.

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INTAPin 11 (Output)


It stands for interrupt acknowledge.

It is an out going signal.It is an active low signal.Low output on this pin

indicates that microprocessor has acknowledged the INTR request.

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Address and Data Pins


127

• Address Bus:

• The address bus is used to send address to memory.

• It selects one of the many locations in memory.

• Its size is 16-bit.

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Address and Data Pins


128

• Data Bus:

• It is used to transfer data between microprocessor and memory.

• Data bus is of 8-bit.

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AD0 – AD7Pin 19-12 (Bidirectional)


• These pins serve the dual purpose of transmitting lower order address and data byte.

• During 1st clock cycle, these pins act as lower half of address.

• In remaining clock cycles, these pins act as data bus.

• The separation of lower order address and data is done by address latch.

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A8 – A15Pin 21-28 (Unidirectional)


• These pins carry the higher order of address bus.

• The address is sent from microprocessor to memory.

• These 8 pins are switched to high impedance state during HOLD and RESET mode.

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ALEPin 30 (Output)


131

• It is used to enable Address Latch.

• It indicates whether bus functions as address bus or data bus.

• If ALE = 1 then– Bus functions as address bus.

• If ALE = 0 then– Bus functions as data bus.

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S0 and S1Pin 29 (Output) and Pin 33 (Output)


• S0 and S1 are called Status Pins.

• They tell the current operation which is in progress in 8085.

S0 S1 Operation

0 0 Halt

0 1 Write

1 0 Read

1 1 Opcode Fetch

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IO/MPin 34 (Output)


133

• This pin tells whether I/O or memory operation is being performed.

• If IO/M = 1 then– I/O operation is being

performed.

• If IO/M = 0 then– Memory operation is being

performed.

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IO/MPin 34 (Output)


• The operation being performed is indicated by S0 and S1.

• If S0 = 0 and S1 = 1 then– It indicates WRITE operation.

• If IO/M = 0 then– It indicates Memory operation.

• Combining these two we get Memory Write Operation.

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Table Showing IO/M, S0, S1 and Corresponding Operations


135

Operations IO/M S0 S1

Opcode Fetch 0 1 1

Memory Read 0 1 0

Memory Write 0 0 1

I/O Read 1 1 0

I/O Write 1 0 1

Interrupt Ack. 1 1 1

Halt High Impedance 0 0

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RDPin 32 (Output)


• RD stands for Read.

• It is an active low signal.

• It is a control signal used for Read operation either from memory or from Input device.

• A low signal indicates that data on the data bus must be placed either from selected memory location or from input device.

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WRPin 31 (Output)


137

• WR stands for Write.

• It is also active low signal.

• It is a control signal used for Write operation either into memory or into output device.

• A low signal indicates that data on the data bus must be written into selected memory location or into output device.

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READYPin 35 (Input)


• This pin is used to synchronize slower peripheral devices with fast microprocessor.

• A low value causes the microprocessor to enter into wait state.

• The microprocessor remains in wait state until the input at this pin goes high.

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HOLDPin 38 (Input)


• HOLD pin is used to request the microprocessor for DMA transfer.

• A high signal on this pin is a request to microprocessor to relinquish the hold on buses.

• This request is sent by DMA controller.

• Intel 8257 and Intel 8237 are two DMA controllers.

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HLDAPin 39 (Output)


140

• HLDA stands for Hold Acknowledge.

• The microprocessor uses this pin to acknowledge the receipt of HOLD signal.

• When HLDA signal goes high, address bus, data bus, RD, WR, IO/M pins are tri-stated.

• This means they are cut-off from external environment.

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HLDAPin 39 (Output)


• The control of these buses goes to DMA Controller.

• Control remains at DMA Controller until HOLD is held high.

• When HOLD goes low, HLDA also goes low and the microprocessor takes control of the buses.

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VSS and VCCPin 20 (Input) and Pin 40 (Input)


142

• +5V power supply is connected to VCC.

• Ground signal is connected to VSS.

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8085 Interrupts

• 5 interrupt pins• Maskable

– INTR– RST5.5, RST6.5, RST7.5

• Non-Maskable– TRAP: cannot be disabled by instruction.

• TRAP has highest priority• Once a interrupt is serviced all interrupts except

TRAP is disabledFaculty of Computer Application,Gharaun


8085 Interrupts• An interrupt is considered to be an emergency signal that

may be serviced.

– The Microprocessor may respond to it as soon as possible.

• What happens when MP is interrupted ?

– When the Microprocessor receives an interrupt signal, it suspends the currently executing program and jumps to an Interrupt Service Routine (ISR) to respond to the incoming interrupt.

– Each interrupt will most probably have its own ISR.


Interrupts• Interrupt is a process where an external device can get the attention of the

microprocessor.– The process starts from the I/O device – The process is asynchronous.

• Classification of Interrupts – Interrupts can be classified into two types:

• Maskable Interrupts (Can be delayed or Rejected)• Non-Maskable Interrupts (Can not be delayed or Rejected)

• Interrupts can also be classified into:• Vectored (the address of the service routine is hard-wired)• Non-vectored (the address of the service routine needs to be

supplied externally by the device)


8085 Interrupts

• When a device interrupts, it actually wants the MP to give a service which is equivalent to asking the MP to call a subroutine. This subroutine is called ISR (Interrupt Service Routine)

• The ‘EI’ instruction is a one byte instruction and is used to Enable the non-maskable interrupts.

• The ‘DI’ instruction is a one byte instruction and is used to Disable the non-maskable interrupts.

• The 8085 has a single Non-Maskable interrupt.

– The non-maskable interrupt is not affected by the value of the Interrupt Enable flip flop.


147

The 8085 Interrupts

Interrupt name Maskable Vectored

INTR Yes No

RST 5.5 Yes Yes

RST 6.5 Yes Yes

RST 7.5 Yes Yes

TRAP No Yes

TRAP

• TRAP is the only non-maskable interrupt.

– It does not need to be enabled because it cannot be disabled.

• It has the highest priority amongst interrupts.

• It is edge and level sensitive.

– It needs to be high and stay high to be recognized.

– Once it is recognized, it won’t be recognized again until it goes low, then high again.

• TRAP is usually used for power failure and emergency shutoff.






8085 Machine cycles

• The 8085 executes several types of instructions with each requiring a different number of operations of different types. However, the operations can be grouped into a small set.

• The three main types are:• Memory Read and Write.• I/O Read and Write.• Request Acknowledge.


Opcode Fetch Machine Cycle

1. Step 1 (State T1): In the state,8085 sends the status signals,IO/M,S1 and S0.IO/M=0,S0=1 and S1=1.

The 8085 sends a 16-bit address on A8-A15 and AD0-AD7.



• The high order byte of program counter is placed on the A8-A15 lines and it remains there upto T3 state. The lower order byte of program counter is placed on the AD0-AD7 lines which remain there only for T7.



• During this state ,ALE gives a positive pulse which represent the content of AD0-AD7 as an address. The ALE signal is used to latch the address to A0-A7.

• NO control signal is generated in this sate.



• Step 2(State T2): • The contents of PC(Lower

address bus) will disappear on AD0-AD7 lines, so that the lines can be used as data lines. The contents if A0 – A7 are still available for memory from external latch.



The control signal RD is made LOW by the processor which enables the read circuit of addressed memory device. The memory device then sends the contents on the data bus i.e. AD0-AD7.

In addition to these operations the MP increments PC by 1.



• Step 3:- (State T3) : During this clock cycle, the data from memory i.e. OPCODE is transferred to instruction register and RD control signal is made HIGH. Thus RD disables the memory device.


Opcode Fetch Machine Cycle• Step 4: (State T4): The

microprocessor performs only internal operation. The OPCODE is decoded by the CPU and upon decoding 8085 knows all the information about:

• (i) Whether it should enter T5 and T6 states.

• (ii) How many bytes of instruction it is?

• If the instruction does not require T5 and T6 states, it will start or go to next machine cycle.


Timing diagram. of Memory cycle

CLK

A15-A8

AD7-AD0

IO/M

RD

MEMRD

A7-A0 A7-A0Data from MPU

Data from memory

WR

MEMWR

T

1

T

2

T

3

ALE

T

1

T

2

T

3

READ Cycle WRITE Cycle04/10/23 158Faculty of Computer Application,Gharaun

Campus,Mohali

READ Cycle

• Step 1(State T1):- In T1 state,8085 sends appropriate status signals,IO/M,S0 and S1. IO/M=0,S=0,S1=1(memory read).The 16-bit address is transferred on AD0-AD7.

• The address is dependant on the operation. In operand fetch cycle, address is given by PC and PC is incremented by 1.In memory read cycle, address depends upon instruction:- Address may be from SP or any General purpose Reg.Pair.

• ALE is generated by 8085 to indicate the availability of address A0-A7 on AD0-AD7.The ALE is used o latch A0-A7.


READ Cycle

• Step -2 (State T2):- In T2 state, the lines ADO-AD7 will be used as D0-D7 to transfer data. The control signal RD is made LOW which will enable the selected memory. The memory will send data on the data bus.


READ Cycle

• Step -3 (State T3) :- In T3 State, data from memory is transferred to 8085. 8085 accepts this data and transfers control on internal data bus and RD is made HIGH.

• Now where the data is transferred depends on the instruction for which this machine cycle is used. it is generally stored in general purpose register.


WRITE Cycle

• Step1(T1) :- In T1 state,8085 sends the appropriate status signals IO/M,S0 and S1.i.e IO/M=0,SO=1,S1=0(memory write).the 16 bit address is transferred on A8-A15 and AD0-AD7.ALE is active for short Duration.


WRITE Cycle

• Step 2(T2) :- In T2 state the address on AD0-AD7 i.e. A0-A7 is removed and data to be stored in memory is transferred on these lines. The control signals WR is made LOW will make memory Active to accept the contents of data bus. The accepted contents are stored at selected location.


WRITE Cycle

• Step3 (State T3):- In this state, data from data bus is stored at memory location .WR is made HIGH which deactivates memory and microprocessor completes the machine cycle.



• B. Ram Fundamentals of microprocessors and HI microcomputers,Dhanpat Rai Publication.



ADDRESSING MODES OF 8085



To perform any operation, we have to give the corresponding instructions to the microprocessor.

In each instruction, programmer has to specify 3 things:Operation to be performed.Address of source of data.Address of destination of result.



The method by which the address of source of data or the address of destination of result is given in the instruction is called Addressing Modes.

The term addressing mode refers to the way in which the operand of the instruction is specified.



Types of Addressing ModesIntel 8085 uses the following addressing

modes:1. Direct Addressing Mode

2. Register Addressing Mode

3. Register Indirect Addressing Mode

4. Immediate Addressing Mode

5. Implicit Addressing Mode



1. Direct Addressing ModeIn this mode, the address of the operand is

given in the instruction itself.

LDA is the operation.2500 H is the address of source.Accumulator is the destination.


LDA 2500 H Load the contents of memory location 2500 H in accumulator.

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2. Register Addressing ModeIn this mode, the operand is in general

purpose register.

MOV is the operation.B is the source of data.A is the destination.


MOV A, B Move the contents of register B to A.

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3. Register Indirect Addressing ModeIn this mode, the address of operand is

specified by a register pair.

MOV is the operation.

M is the memory location specified by H-L register pair.

A is the destination.


MOV A, M Move data from memory location specified by H-L pair to accumulator.

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4. Immediate Addressing ModeIn this mode, the operand is specified within

the instruction itself.

MVI is the operation.05 H is the immediate data (source).A is the destination.


MVI A, 05 H Move 05 H in accumulator.

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5. Implicit Addressing Mode If address of source of data as well as address of destination of result is

fixed, then there is no need to give any operand along with the instruction.

CMA is the operation.

A is the source.

A is the destination.


CMA Complement accumulator.

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Further Reading:-Chapter 4 ,B.RAMTopic no. 4.3 to 4.3.5


INSTRUCTIONS SET OF 8085


INSTRUCTIONS FOR 8085

The instructions are generally classified into the functional categories as follows:-

Data transfer groupArithmetic groupLogical groupBranching groupStack and Machine control group


Data Transfer Group

Data transfer group of instructions copies data from source to destination without modifying the contents of source.

The various types of data transfer that are possible between registers and memory locations as follows:-


Data Transfer Group

S.NO Data Transfer Example

1. Between Registers Reg B Reg D

2. Specific data byte to register or a memory Location

Data Byte Reg B

3. Between Memory Location and Register Mem.Loc. Reg A

4. Between an I/O device and accumulator Input Device Reg. A

5. Between a Reg. Pair and the Stack Reg. Pair data Stack Location


Data Transfer Group

The Data Transfer group of instruction include the Following Instructions:-


1. MOV Rd,Rs 9. LHLD address

2. MOV R,M 10. SHLD address

3. MOV M,R 11. LDAX Rp

4. MVI R,Data 12. STAX Rp

5. MVI M,Data 13. XCHG

6. LXI Rp,16-bit Data

7. LDA address

8. STA address

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Data Transfer Group

1. MOV Rd,Rs


Mnemonic MOV Rd,Rs

Operation Rd=Rs

No.of Bytes 1 byte

Machine Cycle 1 (OF)

Flags No flags are Modified

Algorithm Rd Rs

Addr.Mode Register addressing Mode

T-States 4

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Data Transfer Group

Description:- This instruction copies data from source

register Rs to destination Register Rd.The source register Rs and destination

register Rd can be any general purpose register like A,B,C,D,E,H or L.

The contents of Source register remain unchanged.


Data Transfer Group

Example:- MOV B,CThis instruction will copy the contents of

register C to register B.The contents of Register C remain

unchanged.Suppose B=20H,C=10H and Instruction MOV

B,C is executed. After the execution B=10H and C=10H.


Data Transfer Group

2. MOV R,M


MNEMONIC MOV R,M

Operation R=M or R=(HL)

No.of Bytes 1 byte

Machine Cycle 2(OF+MR)

Flags NO flags are modified

Algorithm R M or R (HL)

Addressing Mode

Indirect Addressing Mode

T-states 4+3=7

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Data Transfer Group

Description:- This instruction Copies data from memory M to

register R. The term M specifies the HL memory Pointer. The

content of HL register pair are used as the address of Memory Location. The contents of that Memory location are transferred to the specified register R.

The register R can be any General purpose register.


Data Transfer Group

Example:- MOV C,M This instruction will copy the data from the memory location

pointed by HL register pair to C register. Let the contents of HL register pair be 2000H,reg C=20H.At

the address 2000H:10H is stored. The HL register pair contents are used as address.i.e HL=2000H.

The contents of memory location 2000H are copied to C register, So Contents of Reg.C, Will change from 20H to 10H.

The contents of Memory location remain unchanged.


Data Transfer Group

3. MOV M,R


MNEMONIC MOV M,R

Operation M=R or (HL)=R

No. of Bytes 1 byte

Machine cycles 2(OF+ MW)

Flags NO Flags are modified

Algorithm M R or (HL) R

Addressing Mode Indirect addressing Mode

T-states 4+3=7

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Data Transfer Group

Description This instruction will copy the data from the register to

memory M. The HL register pair is used as the memory pointer. The

contents of the specified register are copied o that memory location pointed by HL Reg. Pair.

The specified register may be any general purpose reg.A,B,C,D,E,H or L.

The contents of the specified register remains unchanged.


Data Transfer Group

EXAMPLE:-MOV M,C Let the content of HL pair are 2050H. Reg

C=05H, at the address 2050H=25h is stored. On the instruction MOV M,C the data is transferred from C to 2050H.

The contents of the Reg C are copied to memory location 2050H,So contents of Memory location 2050H will change from 25H to 05H.


Data Transfer Group

4. MVI R,Data


MNEMONIC MVI R,DATA

OPERATION R=DATA

No.of bytes 2 bytes

Machine cycle 2(OF+MR)

Flags No flags are Affected

Algorithm R Data

Addressing Mode Immediate addressing Mode

T-states 7(4+3)

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Data Transfer Group

Description:- This instruction moves the 8 bit immediate data to

the specified register. The data is specified within the instruction. It is a 2-byte instruction, so FIRST byte of

instruction will be OPCODE and second byte will be 8-bit data.

The Reg. R may be any General purpose register like A,B,C,D,E,H or L.


Data Transfer Group

EXAMPLE:-MVI D,07This instruction will load the immediate data

07H in Reg.D.Let the contents of Reg D =10H.Then after

execution of instruction MVI D,O7H, the contents of D will change from 10H to 07H.


Data Transfer Group

5. MVI M,Data


MNEMONIC MVI M,DATA

OPERATION M=DATA or (HL)=DATA

NO.OF BYTES 2 BYTES

MACHINE CYCLES 3(OF+MR+MW)

Flags No Flags are affected

Algorithm M data or (HL) data

Addressing Mode Immediate/Indirect addressing Mode

T-States 10(4+3+3)

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Data Transfer Group

Description:-This instruction moves immediate data to

memory.The HL register Pair is used as memory

Pointer. The contents of HL Reg. Pair are used as memory address and immediate data is transferred to that memory location.


Data Transfer Group

Example:-MVI H,10HMVI L, 00HMVI M,20H When the instruction MVI M,2OH is executed

the data 20H will be stored in the memory location addressed by HL pair register.ie 1000H.


Data Transfer Group

6. LXI Rp,16-bit data


Mnemonic LXI Rp,16 bit data

Operation Rp=16 bit data

No.of bytes 3 bytes

Machine Cycle 3(OF+MR+MW)

FLAGS NO flags are affected

Algorithm Rp 16 bit data

Addressing Mode Immediate Addressing Mode

T-states 10(4+3+3)

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Data Transfer Group

Description:- This instruction will load register pair with 16-bit data. This instruction loads 16-bit data specified within the

instruction to the specified register pair or stack pointer. In the instruction only high order register is specified for

register pair.ie if HL only H register will be specified. The register pair Rp can be BC,DE,HL or Stack pointer SP.


Data Transfer Group

Example:- (i)LXI H,2030H Load HL pair with 2030H.i.e 20H will be loaded

in register H and 30H will be loaded in reg L.(ii) LXI SP,2000HLoad SP with 2000H.


Data Transfer Group

7.LDA Address


MNEMONIC LDA Address

Operation A=(address)

No. of Bytes 3 bytes

Machine Cycles 4 (OF+MR+MR+MR)

Flags No flags are effected

Algorithm A (address)

Addressing mode Direct addressing mode

T-states 13(4+3+3+3)

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Data Transfer Group

Description:-Load accumulator direct from MemoryThis instruction copies the contents of the

memory location whose address is specified in the instruction to the accumulator.

The contents of the memory location remain unchanged.


Data Transfer Group

Example:-LDA 3000H This instruction will load the accumulator with the

contents of memory location 3000H. Let initially A=F0H,Contents of memory location

3000H=15H. Then after the execution of instruction LDA

3000H ,the accumulator will be loaded with 15H.the contents of accumulator will change form F0 to 15H.


Data Transfer Group

8.STA Address


MNEMONIC STA address

OPERATION (address)=A

NO of Bytes 3 bytes

Machine Cycles 4(OF+MR+MR+MW)


Algorithm (Address) A

Addressing Mode Direct Addressing Mode

T-states 13(4+3+3+3)

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Data Transfer Group

Description:-Store accumulator direct to memory. This instruction will store the contents of the accumulator to

the memory location specified in the instruction. The contents of memory location remain unchanged. It is 3 byte instruction. The first byte is the opcode,second

byte is Lower order address and third byte is higher order address.


Data Transfer Group

Example:- STA 2050HThis instruction will store contents of

accumulator at memory location 2050H.


Data Transfer Group

9. LHLD Address


Mnemonic LHLD Address

Operation L= (address)H=(address+1)

No. of bytes 3 bytes

Machine cycles 5(OF+MR+MR+MR+MR)


Algorithm L (address) H (address+1)

Addressing mode Direct addressing mode

T-states 16(4+3+3+3+3)

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Data Transfer Group

Description:- Load HL pair directly from memory This instruction loads the contents of the memory location to the H and L

registers. The address of memory is specified along with the instruction. The contents of memory location whose address is specified in the

instruction are transferred to L register and the contents of the next memory location i.e.(address+1) to the H register.

It is 3 byte instruction. The first byte is the opcode,second byte is the lower order address and third byte is the higher order address.


Data Transfer Group

Example:-LHLD 2000H Load HL pair from memory location 2000H and 2001H. Let H=05H,L=04H at memory location 2000H and 2001H the

data 20H and 30H is stored. The instruction LHLD will load the contents of memory

location 2000H to L reg. and contents of 2001H to H reg. So the contents of register L will change from 04 to 20H and

contents of register H will change from 05H to 30H.


Data Transfer Group

10. SHLD Address


Mnemonic SHLD Address

Operation (Address)=L register(Address+1)= H register

No. of bytes 3 bytes

Machine cycle 5(OF+MR+MR+MW+MW)


Algorithm (address) L (address+1) H

Addressing Mode Direct addressing Mode

T-states 16(4+3+3+3+3)

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Data Transfer Group

Description:-STORE HL PAIR DIRECT IN MEMORY1. This instruction copies the contents of registers H and L to the memory

locations.

2. The address of memory location is specified along with the instruction.

3. The contents of L register are stored at the memory location whose address is specified and the contents of the H register to the (address+1) location.

4. It is a three byte instruction. The first byte is the opcode ,second byte is the lower order address and third byte is the higher order address.


Data Transfer Group

Example:-SHLD 3000H1. Store HL pair to memory location 3000 and 3001.2. Let H=05,L=06,at memory locations 3000 and 3001 is

stored and instruction SHLD 3000H is executed ,the contents register L is copied to 3000H and contents of H register is copied to 3001H.


Data Transfer Group

11. LDAX Rp


Mnemonic LDAX Rp

Operation A=(Rp)

No. Of bytes 1 byte

Machine cycles 2(OF+MR)


Algorithm A (Rp)


T-States 7(4+3)

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Data Transfer Group

Description:-Load accumulator indirect by using a memory

pointer.1. This instruction copies the content of the memory location to the

accumulator.

2. The address of memory location is given by Rp register pair specified

along with the instruction.3. The contents of the memory location remain unchanged.


Data Transfer Group

Example:-LDAX B1. This instruction will load accumulator with the contents of

memory location whose address is given by the BC register.2. Let A=1FH, B=20H,C=25H.at memory location 2025=56H is

stored.3. Then after execution of instruction LDAX B,the accumulator

will be loaded with the contents of memory location 2025 i.e. 56H.


Data Transfer Group

12. STAX Rp.


Mnemonic STAX Rp

Operation (Rp)=A

No. of bytes 1 byte

Machine cycles 2(OF+MW)


Algorithm (Rp) A


T-states 7(4+3)

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Data Transfer Group

Description:-Store accumulator indirect by using a memory

pointer1. This instruction copies the contents of accumulator

to memory location.2. The address of memory location is given by Rp

register pair specified along with the instruction.3. The contents of the accumulator remain unchanged.


Data Transfer Group

Example:-STAX D1. This instruction will store contents of accumulator to

the memory location whose address is given by the DE register Pair.

2. Let A= 1FH,D= 26H,E=08H,at memory location 2608:10 is stored.

3. Then after execution of STAX D instruction, the memory location 2608 will contain IFH.


Data Transfer Group

13. XCHG


Mnemonic XCHG

Operation H D L E

No. of bytes 1 byte

Machine Cycles 1(OF)

No. of Flags No flags are effected

Algorithm H D L E

Addressing Mode Register Addressing Mode

T-states 4

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Data Transfer Group

Description:- Exchange the contents of HL with DE pair1.This instruction exchanges the content of H

register with D register and L register with E register.

Example:- XCHG1. Let H =12H,L=11H,D=30H,E=40H, and the

instruction XCHG is executed.Faculty of Computer Application,Gharaun


Arithmetic Instructions

These instructions perform the operations like:

Addition

Subtraction

Increment

Decrement



Addition Any 8-bit number, or the contents of register, or the

contents of memory location can be added to the contents of accumulator.

The result (sum) is stored in the accumulator.

No two other 8-bit registers can be added directly.

Example: The contents of register B cannot be added directly to the contents of register C.



Addition Any 8-bit number, or the contents of register, or the

contents of memory location can be added to the contents of accumulator.

The result (sum) is stored in the accumulator.

No two other 8-bit registers can be added directly.

Example: The contents of register B cannot be added directly to the contents of register C.



Subtraction Any 8-bit number, or the contents of register, or the contents

of memory location can be subtracted from the contents of accumulator.

The result is stored in the accumulator.

Subtraction is performed in 2’s complement form.

If the result is negative, it is stored in 2’s complement form.

No two other 8-bit registers can be subtracted directly.


Increment / Decrement

The 8-bit contents of a register or a memory location can be incremented or decremented by 1.

The 16-bit contents of a register pair can be incremented or decremented by 1.

Increment or decrement can be performed on any register or a memory location.


Arithmetic InstructionsOpcode Operand Description

ADD RM

Add register or memory to accumulator


The contents of register or memory are added to the contents of accumulator.

The result is stored in accumulator.

If the operand is memory location, its address is specified by H-L pair.

All flags are modified to reflect the result of the addition.

Example: ADD B or ADD M

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Opcode Operand Description

ADC RM

Add register or memory to accumulator with carry


The contents of register or memory and Carry Flag (CY) are added to the contents of accumulator.




Example: ADC B or ADC M

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ADI 8-bit data Add immediate to accumulator

The 8-bit data is added to the contents of accumulator.



Example: ADI 45 H

04/10/23 226Faculty of Computer Application,Gharaun Campus,Mohali



ACI 8-bit data Add immediate to accumulator with carry

The 8-bit data and the Carry Flag (CY) are added to the contents of accumulator.



Example: ACI 45 H




DAD Reg. pair Add register pair to H-L pair

The 16-bit contents of the register pair are added to the contents of H-L pair.

The result is stored in H-L pair.

If the result is larger than 16 bits, then CY is set.

No other flags are changed.

Example: DAD B04/10/23 228Faculty of Computer Application,Gharaun

Campus,Mohali



SUB RM

Subtract register or memory from accumulator

The contents of the register or memory location are subtracted from the contents of the accumulator.



All flags are modified to reflect the result of subtraction.

Example: SUB B or SUB M




SBB RM

Subtract register or memory from accumulator with borrow

The contents of the register or memory location and Borrow Flag (i.e. CY) are subtracted from the contents of the accumulator.




Example: SBB B or SBB M




SUI 8-bit data Subtract immediate from accumulator

The 8-bit data is subtracted from the contents of the accumulator.



Example: SUI 45 H




SBI 8-bit data Subtract immediate from accumulator with borrow

The 8-bit data and the Borrow Flag (i.e. CY) is subtracted from the contents of the accumulator.



Example: SBI 45 H




INR RM

Increment register or memory by 1

The contents of register or memory location are incremented by 1.

The result is stored in the same place.

If the operand is a memory location, its address is specified by the contents of H-L pair.

Example: INR B or INR M




INX R Increment register pair by 1

The contents of register pair are incremented by 1.


Example: INX H




DCR RM

Decrement register or memory by 1

The contents of register or memory location are decremented by 1.



Example: DCR B or DCR M




DCX R Decrement register pair by 1

The contents of register pair are decremented by 1.


Example: DCX H


Logical Instructions These instructions perform logical operations on data

stored in registers, memory and status flags.

The logical operations are:ANDORXORRotateCompareComplement


AND, OR, XOR

Any 8-bit data, or the contents of register, or memory location can logically have

AND operation

OR operation

XOR operation

with the contents of accumulator.

The result is stored in accumulator.04/10/23 238Faculty of Computer Application,Gharaun

Campus,Mohali

Rotate

Each bit in the accumulator can be shifted either left or right to the next position.


Compare

Any 8-bit data, or the contents of register, or memory location can be compares for:

Equality

Greater Than

Less Than

with the contents of accumulator.

The result is reflected in status flags.04/10/23 240Faculty of Computer Application,Gharaun

Campus,Mohali

Complement

The contents of accumulator can be complemented.

Each 0 is replaced by 1 and each 1 is replaced by 0.


Logical Instructions


CMP RM

Compare register or memory with accumulator

The contents of the operand (register or memory) are compared with the contents of the accumulator.

Both contents are preserved .

The result of the comparison is shown by setting the flags of the PSW as follows:




CMP RM

Compare register or memory with accumulator

if (A) < (reg/mem): carry flag is set

if (A) = (reg/mem): zero flag is set

if (A) > (reg/mem): carry and zero flags are reset.

Example: CMP B or CMP M




CPI 8-bit data Compare immediate with accumulator

The 8-bit data is compared with the contents of accumulator.

The values being compared remain unchanged.

The result of the comparison is shown by setting the flags of the PSW as follows:




CPI 8-bit data Compare immediate with accumulator

if (A) < data: carry flag is set

if (A) = data: zero flag is set

if (A) > data: carry and zero flags are reset

Example: CPI 89H




ANA RM

Logical AND register or memory with accumulator

The contents of the accumulator are logically ANDed with the contents of register or memory.

The result is placed in the accumulator. If the operand is a memory location, its address is specified by the

contents of H-L pair. S, Z, P are modified to reflect the result of the operation. CY is reset and AC is set. Example: ANA B or ANA M.




ANI 8-bit data Logical AND immediate with accumulator

The contents of the accumulator are logically ANDed with the 8-bit data.

The result is placed in the accumulator.

S, Z, P are modified to reflect the result.

CY is reset, AC is set.

Example: ANI 86H.




XRA RM

Exclusive OR register or memory with accumulator

The contents of the accumulator are XORed with the contents of the register or memory.



S, Z, P are modified to reflect the result of the operation.

CY and AC are reset.

Example: XRA B or XRA M.




ORA RM

Logical OR register or memory with accumulator

The contents of the accumulator are logically ORed with the contents of the register or memory.





Example: ORA B or ORA M.




ORI 8-bit data Logical OR immediate with accumulator

The contents of the accumulator are logically ORed with the 8-bit data.




Example: ORI 86H.




XRA RM

Logical XOR register or memory with accumulator

The contents of the accumulator are XORed with the contents of the register or memory.

The result is placed in the accumulator.If the operand is a memory location, its address is specified by the

contents of H-L pair.S, Z, P are modified to reflect the result of the operation.CY and AC are reset.Example: XRA B or XRA M.




XRI 8-bit data XOR immediate with accumulator

The contents of the accumulator are XORed with the 8-bit data.




Example: XRI 86H.04/10/23 252Faculty of Computer Application,Gharaun

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RLC None Rotate accumulator left

Each binary bit of the accumulator is rotated left by one position.

Bit D7 is placed in the position of D0 as well as in the Carry flag.

CY is modified according to bit D7.S, Z, P, AC are not affected.Example: RLC.




RRC None Rotate accumulator right

Each binary bit of the accumulator is rotated right by one position.

Bit D0 is placed in the position of D7 as well as in the Carry flag.

CY is modified according to bit D0.S, Z, P, AC are not affected.Example: RRC.




RAL None Rotate accumulator left through carry

Each binary bit of the accumulator is rotated left by one position through the Carry flag.

Bit D7 is placed in the Carry flag, and the Carry flag is placed in the least significant position D0.

CY is modified according to bit D7.S, Z, P, AC are not affected.Example: RAL.




RAR None Rotate accumulator right through carry

Each binary bit of the accumulator is rotated right by one position through the Carry flag.

Bit D0 is placed in the Carry flag, and the Carry flag is placed in the most significant position D7.

CY is modified according to bit D0.S, Z, P, AC are not affected.Example: RAR.




CMA None Complement accumulator

The contents of the accumulator are complemented.

No flags are affected.

Example: CMA.




CMC None Complement carry

The Carry flag is complemented.

No other flags are affected.

Example: CMC.




STC None Set carry

The Carry flag is set to 1.

No other flags are affected.

Example: STC.


Branching Instructions

• The branching instruction alter the normal sequential flow.

• These instructions alter either unconditionally or conditionally.


Branching InstructionsOpcode Operand Description

JMP 16-bit address Jump unconditionally

The program sequence is transferred to the memory location specified by the 16-bit address given in the operand.

Example: JMP 2034 H.

This instruction will load the PC with 2034 H and the processor will fetch the instruction from this address.


Description This instruction loads the PC with the address given within the instruction and continues with the program execution from this location

Branching InstructionsOpcode Operand Description

Jx 16-bit address Jump conditionally

The program sequence is transferred to the memory location specified by the 16-bit address given in the operand based on the specified flag of the PSW.

Example: JZ 2034 H.


Description In condition JUMP instruction ,when the condition is true or satisfied then only JUMP is made at the specified address.

If condition is false or not satisfied it will just check and proceed further to execute the next instruction after it.


• Example: JZ 2034 H.• Let Z=0• This instruction will cause a JUMP to an

address 2034 H.i.e PC will load with 2034 as ZF=1.


Jump Conditionally

Opcode Description Status Flags

JC Jump if Carry CY = 1

JNC Jump if No Carry CY = 0

JP Jump if Positive S = 0

JM Jump if Minus S = 1

JZ Jump if Zero Z = 1

JNZ Jump if No Zero Z = 0

JPE Jump if Parity Even P = 1

JPO Jump if Parity Odd P = 0




CALL 16-bit address Call unconditionally

The program sequence is transferred to the memory location specified by the 16-bit address given in the operand.

Before the transfer, the address of the next instruction after CALL (the contents of the program counter) is pushed onto the stack.

Example: CALL 2034 H.




Cx 16-bit address Call conditionally

The program sequence is transferred to the memory location specified by the 16-bit address given in the operand based on the specified flag of the PSW.

Before the transfer, the address of the next instruction after the call (the contents of the program counter) is pushed onto the stack.

Example: CZ 2034 H.04/10/23 266Faculty of Computer Application,Gharaun

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Call Conditionally


CC Call if Carry CY = 1

CNC Call if No Carry CY = 0

CP Call if Positive S = 0

CM Call if Minus S = 1

CZ Call if Zero Z = 1

CNZ Call if No Zero Z = 0

CPE Call if Parity Even P = 1

CPO Call if Parity Odd P = 0




RET None Return unconditionally

The program sequence is transferred from the subroutine to the calling program.

The two bytes from the top of the stack are copied into the program counter, and program execution begins at the new address.

Example: RET.




Rx None Call conditionally

The program sequence is transferred from the subroutine to the calling program based on the specified flag of the PSW.

The two bytes from the top of the stack are copied into the program counter, and program execution begins at the new address.

Example: RZ.04/10/23 269Faculty of Computer Application,Gharaun

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Return Conditionally


RC Return if Carry CY = 1

RNC Return if No Carry CY = 0

RP Return if Positive S = 0

RM Return if Minus S = 1

RZ Return if Zero Z = 1

RNZ Return if No Zero Z = 0

RPE Return if Parity Even P = 1

RPO Return if Parity Odd P = 0




RST 0 – 7 Restart (Software Interrupts)

The RST instruction jumps the control to one of eight memory locations depending upon the number.

These are used as software instructions in a program to transfer program execution to one of the eight locations.

Example: RST 3.


Restart Address Table

Instructions Restart Address

RST 0 0000 H

RST 1 0008 H

RST 2 0010 H

RST 3 0018 H

RST 4 0020 H

RST 5 0028 H

RST 6 0030 H

RST 7 0038 H


Control Instructions

• The control instructions control the operation of microprocessor.




NOP None No operation

No operation is performed.

The instruction is fetched and decoded but no operation is executed.

Example: NOP




HLT None Halt

The CPU finishes executing the current instruction and halts any further execution.

An interrupt or reset is necessary to exit from the halt state.

Example: HLT




DI None Disable interrupt

The interrupt enable flip-flop is reset and all the interrupts except the TRAP are disabled.


Example: DI




EI None Enable interrupt

The interrupt enable flip-flop is set and all interrupts are enabled.


This instruction is necessary to re-enable the interrupts (except TRAP).

Example: EI




RIM None Read Interrupt Mask

This is a multipurpose instruction used to read the status of interrupts 7.5, 6.5, 5.5 and read serial data input bit.

The instruction loads eight bits in the accumulator with the following interpretations.

Example: RIM


RIM Instruction




SIM None Set Interrupt Mask

This is a multipurpose instruction and used to implement the 8085 interrupts 7.5, 6.5, 5.5, and serial data output.

The instruction interprets the accumulator contents as follows.

Example: SIM


SIM Instruction
