basics of electrical measurement

8/10/2019 Basics of Electrical Measurement

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Formative Assessment

Ashesh B Vignesh

110110013

I.C.E. Department

20102014 Batch

Microprocessors andMicrocontrollers

Unit 1


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Introduction

Definition: A microprocessor is a multipurpose,programmable, clockdriven, registerbased

electronic device that reads binary instructions

from a storage device called memory, accepts

binary data as input and process data

according to those instructions and provides

results as output


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Introduction

Basically, very similar to human brain

Physical Components are calledhardware

Set of instructions written for microprocessor

called a programA group of programsis called software

8085 is an 8 bitmicroprocessor

8086 is a 16 bit microprocessor


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Microprocessor as a CPU (MPU)

Traditionally the computer is represented by a) infigure

Diagram shows that has four components:

memory, input, output and the CPU, which

consists of the ALU

CPU contains various registers to store data, the

ALU to perform arithmetic and logical operations

etc.

It communicates with I/O devices either to accept

or send data

These devices are also known as peripherals

CPU is the primary and central player in


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It became possible to build the CPU on a singlechip: this came to be known as a microprocessor

The new block diagram is shown b)

A computer with a microprocessor as its CPU is amicrocomputer

c) shows the microcontroller chip also includes

additional devices such as an A/D convertor,

serial I/O etc.


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Memory

Memory stores such binary informations asinstructions and data

Provides that information to microprocessor when

necessary

To execute programs, microprocessor reads

instructions and data from memory

There are two type of memory

ReadOnly Memory (ROM) Read/Write Memory (R/WM) also known as (RAM)


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ROM

ROM is used to store programs that do not needalterations

Monitor program of a singleboard

microcomputer is stored in ROM

Programs stored in ROM can be only read, not

altered


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RAM

RAM is also known as user memory

It is used to store user programs and data

In singleboard microcomputers, the monitor

program monitors the HEX keys, and storesthose instructions and data in RAM

The information stored in this memory can be

easily read and altered


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MPU initiated operations and BUS

organization

MPU performs primarily performs 4 operations Memory Read

Reads data or instructions from memory

Memory Write

Writes data or instructions into memory

I/O Read

Accepts data from input devices

I/O Write

Sends data to output devices


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MPU initiated operations and BUS

organization

Operations are part of communication process

between the MPU and peripheral devices

To communicate with peripheral, MPU needs to

perform following steps: Step 1: Identify the peripheral or the memory location

Step 2: Transfer binary information

Step 3: Provide timing or synchronization signals

Provides functions using 3 sets of communicationlines:

Address bus, Data bus and Control bus


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8085 Bus Structure


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Address Bus

Address bus is group of 16 lines generallyidentified asto

Address bits are unidirectionalfrom MPU to

peripheral devices

The MPU uses the address bus to perform the

first step

Each memory location is identified by a binary

number called addressAddress bus is used to carry a 16bit address


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Control Bus

Comprised of various single lines that carrysynchronization signals

Uses such lines to perform step 3

These lines provide a pulse to indicate an MPU

operation

MPU generates specific control signals for every

operation it performs

These signals are used to identify a device typewith which the MPU intends to communicate


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8085 Logic Pinout and Signals


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Signals of 8085

There are 6 groups of control and status signalsAddress Bus

Data Bus

Control and Status signals

Power supply and frequency signals

Externally initiated signals

Serial I/O Ports


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Address Bus

8085 has 16 pins used as address bus Split into two segments: A15A8and AD7AD0

A15A8are unidirectional

Used for most significant bits called highorder

address

AD7AD0are used for a dual purpose


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Multiplexed Address/Data Bus

AD7AD0are bidirectional and serve dualpurpose

Used as loworder address bus and data bus

When executing instruction:

Earlier part of cycle: loworder address bus

Later part of cycle used as data bus

Known as multiplexing the bus

Loworder bus can be separated by using alatch


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Control and Status signals

There are 6 main signals

Two control signals

and

Three status signals

/, and

Identify the nature of the operation

One special signal

Indicate beginning of operation


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Control Signal

ReadA Read control signal (active low)

Indicates selected /or memory device is to be

read

Indicates data available on the data bus

Write

Write control signal (active low)

Indicates the data on data bus are to be written into

selected memory or /location


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Status Signals

/- Input/Output or Memory Signal used to differential between I/O and memory

operation

When High, it indicates I/O operation

When Low, it indicates memory operation

Combined with and to generate I/O and

Memory control signals

and

Similar to

Can identify various operations but rarely used in

small systems


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Machine Cycle Status and Control

Signal


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Power Supply and Clock

Frequency

+5 V Power Supply

Ground Reference

, 2

A crystal (or RC, LC) network is connected at these

two pins

To operate at 3 MHz, crystal should have afrequency of 6 MHz

()

Clock output: This signal can be used as the system

clock for other devices


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Externally Initiated Signals, Including

Interrupts

8085 has 5 interrupt signals Used to interrupt program execution

Microprocessor acknowledges an interrupt

request by (Interrupt Acknowledge) signal

Three pins - , and

Accept externally initiated signals as input


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Interrupts

To respond to Request, there is a signalcalled (HOLD Acknowledge)

:

: When signal in this pin goes low,

program counter set to zero Buses are tristated and MPU is reset

: Indicates that MPU is being reset

Cen be used to reset other devices

The other interrupts are shown in the table


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Interrupt signals


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Serial I/O Ports

There are two signals to implement serialtransmission

(Serial Input Data)

(Serial Output Data)

During serial transmission, data bits are sent over

a single line, one bit at a time, such as the

transmission over telephone lines


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Detailed look at 8085 architecture

The 8085 consists of the following:ALU (Arithmetic/Logic Unit)

Timing and Control Unit

Instruction Register and Decoder

Register Array

Interrupt Control

Serial I/O Control


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Block Diagram of 8085 Architecture


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The ALU

Performs computing functions Includes:

The accumulator

Temporary register

The arithmetic and logic circuits

Five Flags

The temporary register holds date during an

arithmetic/logic operation Result stored in accumulator

Flags are set or reset according to the result of

the operation


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ALUFlags

S

SignflagAfter an arithmetic or logic operation, if bit 7of the

result (usually in accumulator) is 1, the Sign flag is

set

In a given byte, if 7is 1, number is negative,otherwise if 0, it is positive

In arithmetic operations with signed numbers, bit 7

is reserved for indicting sign

Remain 7 bits are for magnitude of number For unsigned numbers, value of bit 7is irrelevant

to the sign of number (positive or negative)


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ALUFlags

Z

Zero Flag Zero flag is set if ALU operation results in 0

Flag is reset if result is not 0

Flag is modified by results in accumulator as well as

other registers AC Auxiliary Carry Flag

In arithmetic operation, when carry is generated bybit 3and passed to 4, AC flag is set

Used only internally for Binary Coded Decimal(BCD) operations

Not available for programmer to change sequenceof program with jump instruction


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ALU - Flags

P

Parity Flag If result of operation has an even number of 1s, flag

is set (e.g. 0000 0011)

If there is odd number of 1s, flag is reset (e.g. 0000

0111) CYCarry Flag

If operation results in carry, the Carry flag is set

Otherwise, reset

Also serves as the borrow flag for subtraction


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ALU - Flags

The bit positions reserved for these flags in theflag register are as follows

AC Flag is used internally for BCD arithmetic

Instruction set does not include any conditional

jump instructions based on the AC flag

Z and CY flags are most commonly used


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Timing and Control Unit

This unit synchronizes all operations with clock Generates control signals necessary for

communication between processor and

peripherals

Similar to a sync pulse in an oscilloscope

The and signals are sync pulses

Indicating availability of data on data bus


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Instruction register and Decoder

Instruction register and Decoder are part of ALU When instruction is fetched from memory. It is

loaded in the instruction register

Decoder decodes instruction and establishes

sequence of events to follow

Instruction register is nonprogrammable and

not accessible through instructions


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8086 microprocessor

Inter iAPX 8086 is a 16bit microprocessor Housed in 40pin package

Capable of addressing 1 MB of memory

Various versions can operate with clockfrequencies from 5 MHz to 10 MHz


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8086 Architecture

The 8086 has a 16bit external data bus Signals of the 8086 are classified in seven

categories

1) Address bus

2) Data Bus

3) Control and status signals

4) External requests

5) Response to external requests

6) Power and clock

7) Signals for micro processing environment

The first six categories are the same as the 8085


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8086 Architecture Figure


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8086 Architecture

The 7thcategory, Signals for multiprocessorenvironment, is a new

It includes 2 signals

/(minimum or maximum mode)

Test

The data bus and status signals are multiplexed

with the address bus

16 data lines,15 0are multiplexed


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Signals different from 8085

/- Minimum/Maximum mode Represents two operation modes; minimum and

maximum

When signal is high (connected to +5 V): Minimum

When signal is low (grounded): Maximum Minimum mode used for single processor

environment

Maximum mode used for multiprocessor

environment In Maximum mode, 8 pins assigned different

functions as compared to maximum mode

Bus controller is necessary to generate control signals

Mi i /M i d t l


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Minimum/Maximum mode control

signals


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Test Used to synchronize operations of multiple

processors in a system

When WAIT instruction is being executed,

processor checks this signal If high, processor interrupts execution of program

If low, it continues execution

- Data Enable

Active low output signal

Generally connected to bidirectional buffer to isolate

MPU from system bus


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/- Data Transmit/Receive Connected to a bidirectional buffer to enable data

flow

/- Memory and I/O

Indicates whether processor cycle is I/O operationor memory operation

- Bus High Enable

Active low signal used to enable the highorder

byte of 16bit data


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Stack

Stack can be described as a set of memorylocations in R/W memory

Beginning of the stack is defined in the program

by using instruction LXI SP

Loads a 16bit memory address in the stackpointer register of the micro processor

Once stack location defined, storing of data bytes

startsat the memory address that is 1 less that

the address in the stack pointer register


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Stack

As a general practice, the stack is initalized at thehighest avaible memory location

To prevent the program from being destroyed by the

stack information

Size of stack is limited only by

Data bytes in register pairs of the microprocessor

can be stored on the stack

Stored (two at a time) in reverse order (decreasing

memory address)

By using instruction PUSH


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Stack

Data byte can be transferred from stack torespective registers by using instruction POP

Stack pointer register tracks the storage and

retrieval of the information

Because two bytes are stored at a time

16bit memory address in stack pointer register is

decremented by two

When retrieved, address is incremented by two


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Stack


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Stack


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Subroutine

Group of instructions written separately from mainprogram to perform a function that occurs

repeatedly in the main program

There are two instructions to implement

subroutine CALL (Call a subroutine)

RET (Return to main program)


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Subroutine

When subroutine is called, the contents of theprogram counter is stored on the stack

Program execution is transferred to subroutine

address

When RET is executed, memory address stored

on the stack is retrieved and sequence of

execution is resumed to main program


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Subroutine


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Registers

The operations with the microprocessor performsare:

Store 8bit data

Perform arithmetic and logical operations

Test for conditions Sequence for execution of instructions

Store data temporarily during the execution in the

defined R/W memory locations called stack


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Registers

To perform operations, the microprocessorrequires registers, ALU, and BUS

Registers store data or instructions

There are a total of 9 registers which is of

importance

6 General Purpose registers

2 Special Registers

1 Main Register


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Registers


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Registers

The 6 general purpose registers are: B, C, D, E,H and L

Each register is 8 bits long

Can be combined to give register pairs

B-C, D-E, H-L

Each register pair will then be 16 bits long


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Registers

The accumulator is an 8 bit register that is part ofthe ALU

This register is used to store 8 bit data and to

perform arithmetic and logical operations

Used as a register for storing on data when twoare arithmetically operated

The result of the operation is stored also in the

accumulator which is identified as A.

When only one data is to be logically operated, A

is used for storing data and for storing result after

operation


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Special Registers

The program counter (PC) is a 16 bit specialfunction register in the 8085 microprocessor.

Sequences execution of instruction

Keeps track of memory address of next

instruction once current is executed In other words, holds address of memory of next

instruction when current instruction is completed

When user enters a memory address and

presses execute key, it is pushed into PC Once processor begins execution, it places the

memory address user entered into address bus


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Program Counter

The address in PC is incremented for nextoperation

Once execution is done, the next address in

placed on address bus, and PC is incremented

again It basically points next location of memory where

data can be stored


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Stack

Stack can be defined as:A set of memory locations in the R/W memory,

specified by a programmer in a main program

These memory locations are used to store binary

information (bytes) temporarily during executionof a program

The location of the stack is defined by the stack

pointer

The stack pointer is a 16bit register

Used as a memory pointer to identify the stack

Used when interrupt is generated by

microprocessor


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Stack

The beginning of the stack is defined in theprogram by using the instruction LXI SP (e.g. LXI

SP, 2099H)

This instruction loads a 16bit memory address

in the stack pointer Once stack location defined, storing of data bytes

begins at memory address that is one less than

address in SP

For example, if SP is loaded with address 2099H,

the storing of data bytes begins at 2098H

The rest of the data is stored in reverse order

(2097H, 2096H...)


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Stack

We call this as the stack growing backwards Hence, stack is initialized at highest available

memory location to prevent program from being

destroyed

The size of the stack is limited only by theavailable memory

The 8085 provides two instructions: PUSH and

POP for storing information on the stack and

retrieving it back

Information is saved on the stack by PUSHing it

on

It is retrieved from the stack by POPing it off.


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PUSH

PUSH is a 1 byte instruction Example: PUSH B (B has value 12 and C has

value F3)

The process of how PUSH works:

First, decrease SP by one

Then copy contents of register B to memory

location pointed now by SP after decrement

Decease SP by one again

Copy contents of register C to location pointed by

SP


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POP

POP is a 1 byte instruction For example POP D (used after PUSH B from last

slide)

Process of how POP works:

Copy contents of memory location pointed by SP to

register E

Increase the SP by 1

Copy contents of memory location pointed by SP to

register D after increment

Increase SP


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Stack

Note: operands B, D and H represent registerpairs BC, DE and HL respectively

During pushing, the stack operates in adecrement then store style.

The stack pointer is decremented first, then theinformation is placed on the stack.

During popping, the stack operates in a use thenincrement style. The information is retrieved from the top of the

stack and then the pointer is incremented.

The SP pointer always points to the top of thestack.


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LIFO

LIFO is an acronym When expanded, it becomes Last In First Out

This is how the stack operations work, where the lastbyte to be stored will be retrieved first

To retrieve information back into original location, onemust make order of PUSH and POP opposite to eachother

Example:

PUSH B

PUSH D POP D

POP B

If the POP instructions are reversed, there will be an

exchange of contents of BC and DE register pairs


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8 Bit Addition

Start program by loading the first data intoaccumulator

Load the second data into other register

Add the contents of the two registers

Check for carry

Store the value of sum and carry in memory

location

Terminate the program


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Program

Loop Memory Instruction Op Code Comment4100 MVI C, 00H OE

Initialise C to 00H4101 OO

4102 LDA, 4200H 3A

Load the 1st data in A4103 OO

4104 42

4105 MOV B,A 47 Move Content of A to B

4106 LDA, 4201H 3A

Load the 2nd data4107 O14108 42

4109 ADD B 80 Add B to A

410A JNC 410EH O2

Jump on no carry410B 0E

410C 41

410D INR C OC Increment content of S

LOOP 410E STA, 4400H 32

Store the content of A to 4400H410F OO

4110 44

4111 MOV A, C 79 Move the content of C to A

4112 STA, 4401H 32

Store the content of A to 4401H4113 O1

4114 44

4115 HLT 76 Terminate the Program


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16 Bit addition

Algorithm Start the program by loading HL register pair with

address of 1stnumber.

Copy the data to DE register pair.

Load the second number to HL pair.

Add the two register pair contents.

Check for carry.

Store the value of sum and carry in memorylocations.

Terminate the program.


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ProgramLoop Memory Instructions Opcode Comment

4200 MVI C, OO OE Initialize C a 04201 OO

4202 LHLD 4500 2A

Load address of 1st number to HL pair4203 OO

4204 45

4205 XCHG EB Copt 1st number to DE pair

4206 LHLD 4502 2A

Load address of 2nd number to HL pair4207 O24208 45

4209 DAD A 19 Add HL pair with DE pair

420A JNC LOOP D2

JUMP on no carry to the label LOOP420B OE

420C 42

420D INR C OC Increment C by 1

LOOP 420E SHLD 4100 22

Store HL pair content to 4100420F OO

4210 41

4211 MOV A, C 79 Contents of C copied to A

4212 STA 4102 32

Store accumulator content to 41024213 O2

4214 41

4215 HLT 76 Program Ends


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8 Bit subtraction

Start the program by loading the first data intoaccumulator

Load the second data into other register

Subtract the second register data from the

accumulator

Check for positive

Store the result in some memory location

Terminate the program


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ProgramLoop Memory Instruction Op Code Comment

4100 MVI C, 00H OEInitialise C to 00H

4101 OO

4102 LDA, 4200H 3A

Load the first Data4103 OO

4104 42

4105 MOV B,A 47 Move contents of A to B

4106 LDA, 4201H 3A

Load the 2nd data4107 O14108 42

4109 SUB B 90 Subtract B from A

410A JP LOOP F2

Jump if Positive410B 0E

410C 41

410D DCR C OD Decrement C

LOOP 410E STA, 4300H 32

Store value in A410F OO

4110 43

4111 MOV A, C 79 Move contents to C

4112 STA, 4301H 32

Store value in A4113 O1

4114 43

4115 HLT 76 Terminate Program


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16 Bit Subtraction Start the program by loading HL register pair with address of

1stnumber.

Copy the data to DE register pair.

Load the second number to HL pair.

Copy data in register E to Accumulator.

Copy date in register L to register B.

Subtract data in register B from Accumulator.

Check for carry.

If carry is present take 2s complement of Accumulator.

Store the difference value in the memory location.

Copy data in register D to Accumulator.

Subtract data in register H from Accumulator along with borrow. Check for carry.

If carry is present take 2s complement of Accumulator.

Store the difference value and borrow in the memory location.

Terminate the program.


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ProgramLoop Memory Instructions Opcode Comment

4400 LHLD 4600 2A

Load 1st number's address to HL pair4401 OO

4402 46

4403 XCHG EB Exchange between HL and DE pair

4404 LHLD 4602 2A

Load address of 2nd number to HL pair4405 O2

4406 46

4407 MVI C, 00 OEInitialize C as 0

4408 OO

4409 MOV A, E 7B Copy contents of E to accumulator

440A MOV B, L 45 Copy content of register L to B

440B SUB B 90 Subtract B from Accumulator440C JNC LOOP D2

Jump on no carry to label LOOP440D 11

440E 44

440F CMA 2F Compliment accumulator content

4410 INR A 3C Increment accumulator content by 1


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Program

LOOP 4411 STA 4300 32Store accumulator content to 43004412 OO

4413 43

4414 MOV A,D 7A Copy content of D to accumulator

4415 SBB H 9C Subtract content of H from accumulator with borrow

4416 JNC LABEL D2

Jump on no carry to label LABEL4417 1C

4418 444419 INR C OC Increment C by 1

441A CMA 2F Compliment accumulator content

441B INR A 3C Increment accumulator content by 1

LABEL 441C STA 4301 32

Store accumulator content to 4301441D O1

441E 43

441F MOV A, C 79 Copy carry to accumulator

4420 STA 4302 32

Store the accumulator content to 43024421 O2

4422 43

4423 HLT 76 Program ends


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8085 Instruction Set

We shall now see the 8085 instruction set


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MOV

Copy from source to destination

MOV Rd, Rs

M, Rs

Rd, M

This instruction copies the contents of the sourceregister into the destination register

The contents of the source register are notaltered

If one of the operands is a memory location, itslocation is specified by contents of the HL

registers.


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MVI

Move immediate 8-bit

MVI Rd, data

M, data

The 8-bit data is stored in the destination register

or

M, data memory If the operand is a memory location, its location is

specified by the contents of the HL registers

Example: MVI B, 57H or MVI M, 57H


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LDA

Load accumulator

LDA 16-bit address

Contents of a memory location, specified by a 16-

bit address in the operand, are copied to the

accumulator

The contents of the source are not altered Example: LDA 2034H


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LDAX

Load accumulator indirect

LDAX B/D Reg. pair

The contents of the designated register pair point

to a memory location

This instruction copies the contents of that

memory

location into the accumulator The contents of either the register pair or the

memory location are not altered

Example: LDAX B


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LXI

Load register pair immediate

LXI Reg. pair, 16-bit data

The instruction loads 16-bit data in the register

pair designated in the operand

Example: LXI H, 2034H or LXI H, XYZ


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LHLD

Load H and L registers direct

LHLD 16-bit address

The instruction copies the contents of thememory location pointed out by the 16-bit

address into register L

It copies the contents of the next memory location

into register H

The contents of source memory locations are not

altered

Example: LHLD 2040H


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STA

Store accumulator direct

STA 16-bit address

The contents of the accumulator are copied into

the memory location specified by the operand

This is a 3-byte instruction

The second byte specifies the low-order addressand the third byte specifies the high-order

address

Example: STA 4350H


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STAX

Store accumulator indirect

STAX Reg. pair

Contents of accumulator are copied into memory

location specified by contents of operand

The contents of the accumulator are not altered

Example: STAX B


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SHLD

Store H and L registers direct

SHLD 16-bit address

The contents of register L are stored into thememory location specified by the 16-bit address

in the operand

The contents of H register are stored into the next

memory location by incrementing the operand

The contents of registers HL are not altered

The second byte specifies the low-order address

and the third byte specifies the high-order


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PUSH Push register pair onto stack

PUSH Reg. pair

The contents of the register pair designated in theoperand are copied onto the stack in the following

sequence

The stack pointer register is decremented and the

contents of the high order register are copied into thatlocation

Stack pointer register is decremented again

The contents of the low-order register are copied to

that location


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POP

Pop off stack to register pair

POP Reg. pair

Contents of the memory location pointed out by

the stack pointer are copied to the low-order of

operand

Stack pointer is incremented by 1 The contents of that memory location are copied

to the high-order register of the operand

The stack pointer register is again incremented

by 1


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OUT

Output data from accumulator to a port with 8-bitaddress

OUT 8-bit port address

The contents of the accumulator are copied into

the I/O port specified by the operand

Example: OUT F8H


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IN

Input data to accumulator from a port with 8-bitaddress

IN 8-bit port address

The contents of the input port designated in the

operand are read and loaded into the

accumulator

Example: IN 8CH


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ADD Add register or memory to accumulator

ADD R

M

The contents of the operand are M added to the

contents of the accumulator

The result is stored in the accumulator. If the operand

is a memory location Its location is specified by the contents of the HL

registers

All flags are modified to reflect the result of the

addition


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ADC

Add register to accumulator with carry

ADC R

M

The contents of the operand and M the Carry flag are

added to the contents of the accumulator

The result is stored in the accumulator

If the operand is a memory location, its location is


All flags are modified to reflect the result of the

addition.


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SUB

Subtract register or memory from accumulator

SUB R

V

The contents of the operand (register or memory) are subtracted from the contents of theaccumulator

The result is stored in the accumulator

If the operand is a memory location, its location isspecified by the contents of the HL registers

All flags are modified to reflect the result of thesubtraction.

Example: SUB B or SUB M


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SBB Subtract source and borrow from accumulator

SBB R

M

The contents of the operand the Borrow flag aresubtracted from the contents of the accumulator

The result is placed in the accumulator

If the operand is a memory location, its location isspecified by

the contents of the HL registers

All flags are modified to reflect the result of thesubtraction

Example: SBB B or SBB M


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INR

Increment register or memory by 1

INR R

M

The contents of the designated register or

memory are incremented by 1

The result is stored in the same place If the operand is a memory location, its location is


Example: INR B or INR M


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INX

Increment register pair by 1

INX R

The contents of the designated register pair are

incremented by 1

The result is stored in the same place

Example: INX H


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DCR

Decrement register or memory by 1

DCR R

M

The contents of the designated register or

memory are decremented by 1

The result is stored in the same place If the operand is a memory location, its location is


basics of electrical measurement

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