mICROPROCESSOR UNIT 1 ALL.pptx

DISCOVER . LEARN . EMPOWER
UNIVERSITY INSTITUTE
ENGINEERING
DEPARTMENT OF COMPUTER
SCIENCE & ENGINEERING
Bachelor of Engineering
SUBJECT NAME: MICOPROCESSOR & INTERFACING
SUBJECT CODE : CST-252
By
Dr. Mamta Arora
TOPIC NAME: Introduction to the course,
Introduction to microprocessor

2
COURSE OBJECTIVES
https://www.intel.com/content/www/us/en/educatio
n/k12/the-journey-inside/explore-the-
curriculum/microprocessors.html
S. No. Objectives
1
To understand the concept of the data structures and
operations on them.
2
To apply different data structures for modeling real world
problems.
3
To provide basic data structure concepts in an object-oriented
setting for design, implementation, testing and maintenance of
software systems.

3
COURSE OUTCOMES
https://petnitro.weebly.com/blog/
memory-interfacing-in-8085-
microprocessor-pdf
CO
Number
Title Level
CO1
To understand the basic concepts of Microprocessor
based computer system. Understand
CO2
To identify detailed software & hardware structure
of the Microprocessor. Identify
CO3
To classify the instruction set of microprocessor and
apply it in assembly language programming Apply
CO4
To analyse and develop assembly language
programs for target microprocessor. Analyse
CO5
To evaluate and Design the application specific
programming models with microprocessor Evaluate

IMPORTANCE OF COURSE
• Microprocessor is an important part of
a computer architecture without which
you will not be able to perform
anything on your computer.
• Microprocessor is a digital device on a
chip which can fetch instruction from
memory, decode and execute them and
give results.
4
https://www.geeksforgeeks.org/introduction-of-
microprocessor/#:~:text=A%20Microprocessor%20is%
20an%20important,it%20and%20produce%20desired
%20output.

SYLLABUS
Unit-I [15h]
• Chapter -1(Introduction)
• Review of Hardwired Logic v/s Flexible Logic, Tri State Logic.
Introduction to microprocessor, Difference between microprocessor
and microcomputer, Basic components of a microprocessor, system
bus: address, data and control buses.
• Chapter -2(8085 microprocessor)
• Architecture, pin diagram, flags, addressing modes, instruction set-
classification and applications, assembly language programming,
timing diagrams.
5

SYLLABUS
Unit-II [15h]
• Chapter -3 (Interfacing devices)
• Architecture, Block Diagram, Control words, Modes and working of8255.
• Architecture, Block Diagram and working of8251
• Chapter -4 (8085 Applications )
• Interfacing- Seven Segment LED display, Traffic control system.
6

SYLLABUS
Unit-III [15h]
• Chapter -5 (8086 Microprocessor)
• Architecture, block diagram and pin diagram of 8086, operating modes of 8086,
details of sub-blocks such as EU, BIU; memory segmentation and physical address
computations, program relocation, addressing modes.
• Chapter-6 (Advanced microprocessors)
• Introduction to 80186, 80286, 80386, 80486, Pentium microprocessors.
•
• ADVANCED TOPICS (BEYOND SYLLABUS)
• Design of interfacing circuits
7

Recommended Books
Text Books:
1. Gaonkar, Ramesh S., “Microprocessor Architecture, Programming &
Applications with 8085”, Wiley EasternLtd.
2. Ayala, “The 8086 Microprocessor: Programming & Interfacing the PC” ,
Cengage Learning.
Bhurchandi, K.M, Ray, A.K, “Advanced microprocessors and
peripherals”,TMH.
Reference Books:
1.Brey, “The Intel Microprocessors 8086- Pentium processor”,PHI.
2. Triebeland Singh, Avtar, “The 8088 & 8086 Microprocessors-Programming,
interfacing, Hardware & Applications”,PHI
8

•Microprocessors are integrated
electrical circuits that are capable of
carrying out the instructions of a
computer software application or
program.
•A device that uses a
microprocessor is normally capable
of many functions, such as word
processing, calculation, and
communication via Internet or
telephone.
9
INTRODUCTION TO MICROPROCESSOR
https://www.daenotes.com/electronics/digital-
electronics/Intel-8085-8-bit-microprocessor
Fig.1

CONTD…
• The central processing unit (CPU) is a chip that functions as the brains
of the computer.
• It is made of transistors--millions of transistors, in fact. Microprocessors
are the circuitry that surround the CPU.
• The microprocessor is more than the CPU.
• It contains other processors, for example, the graphics processor unit.
Sound cards and network cards are encased in microprocessors.
• So a CPU is part of a microprocessor, but a microprocessor is more
than the CPU.
10

Basic Concepts
• Differences between:
– Microcomputer – a computer with a microprocessor as its CPU.
Includes memory, I/O etc.
– Microprocessor – silicon chip which includes ALU, register
circuits & control circuits
– Microcontroller – silicon chip which includes microprocessor,
memory & I/O in a single package.
11

What is a Microprocessor?
• The word comes from the combination micro and processor.
– Processor means a device that processes whatever. In this context processor
means a device that processes numbers, specifically binary numbers, 0’s and
1’s.
• To process means to manipulate. It is a general term that describes all manipulation.
Again in this content, it means to perform certain operations on the numbers that depend
on the microprocessor’s design.
12

What about micro?
• Micro is a new addition.
– In the late 1960’s, processors were built using discrete
elements.
• These devices performed the required operation, but were too
large and too slow.
– In the early 1970’s the microchip was invented. All of
the components that made up the processor were now
placed on a single piece of silicon. The size became
several thousand times smaller and the speed became
several hundred times faster. The “Micro”Processor
was born.

Was there ever a “mini”- processor?
• No.
– It went directly from discrete elements to a
single chip. However, comparing today’s
microprocessors to the ones built in the early
1970’s you find an extreme increase in the
amount of integration.
• So, What is a microprocessor?

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

Definition (Contd.)
• Lets expand each of the underlined words:
– Programmable device: The microprocessor can perform
different sets of operations on the data it receives depending
on the sequence of instructions supplied in the given
program.
By changing the program, the microprocessor manipulates
the data in different ways.
– Instructions: Each microprocessor is designed to execute a
specific group of operations. This group of operations is
called an instruction set. This instruction set defines what the
microprocessor can and cannot do.

Definition (Contd.)
– Takes in: The data that the microprocessor
manipulates must come from somewhere.
• It comes from what is called “input devices”.
• These are devices that bring data into the system
from the outside world.
• These represent devices such as a keyboard, a
mouse, switches, and the like.

Definition (Contd.)
– Numbers: The microprocessor has a very narrow view on life. It
only understands binary numbers.
A binary digit is called a bit (which comes from binary digit).
The microprocessor recognizes and processes a group of bits
together. This group of bits is called a “word”.
The number of bits in a Microprocessor’s word, is a measure of its
“abilities”.

Definition (Contd.)
– Words, Bytes, etc.
• The earliest microprocessor (the Intel 8088 and Motorola’s
6800) recognized 8-bit words.
– They processed information 8-bits at a time. That’s why they are
called “8-bit processors”. They can handle large numbers, but in
order to process these numbers, they broke them into 8-bit pieces
and processed each group of 8-bits separately.
• Later microprocessors (8086 and 68000) were designed with
16-bit words.
– A group of 8-bits were referred to as a “half-word” or “byte”.
– A group of 4 bits is called a “nibble”.
– Also, 32 bit groups were given the name “long word”.
• Today, all processors manipulate at least 32 bits at a time and
there exists microprocessors that can process 64, 80, 128 bits

Definition (Contd.)
– Arithmetic and Logic Operations:
• Every microprocessor has arithmetic operations such as add
and subtract as part of its instruction set.
– Most microprocessors will have operations such as multiply and
divide.
– Some of the newer ones will have complex operations such as
square root.
• In addition, microprocessors have logic operations as well.
Such as AND, OR, XOR, shift left, shift right, etc.
• Again, the number and types of operations define the
microprocessor’s instruction set and depends on the specific
microprocessor.

Definition (Contd.)
– Stored in memory :
• First, what is memory?
– Memory is the location where information is kept while not in
current use.
– Memory is a collection of storage devices. Usually, each storage
device holds one bit. Also, in most kinds of memory, these
storage devices are grouped into groups of 8. These 8 storage
locations can only be accessed together. So, one can only read or
write in terms of bytes to and form memory.
– Memory is usually measured by the number of bytes it can hold.
It is measured in Kilos, Megas and lately Gigas. A Kilo in
computer language is 210 =1024. So, a KB (KiloByte) is 1024
bytes. Mega is 1024 Kilos and Giga is 1024 Mega.

Definition (Contd.)
– Stored in memory:
• When a program is entered into a computer, it is
stored in memory. Then as the microprocessor starts
to execute the instructions, it brings the instructions
from memory one at a time.
• Memory is also used to hold the data.
– The microprocessor reads (brings in) the data from
memory when it needs it and writes (stores) the results
into memory when it is done.

Definition (Contd.)
– Produces: For the user to see the result of the
execution of the program, the results must be
presented in a human readable form.
• The results must be presented on an output device.
• This can be the monitor, a paper from the printer, a
simple LED or many other forms.

Memory
Output
Input
A Microprocessor-based system
From the above description, we can draw the
following block diagram to represent a
microprocessor-based system:

Inside The Microprocessor
• Internally, the microprocessor is made up of
3 main units.
– The Arithmetic/Logic Unit (ALU)
– The Control Unit.
– An array of registers for holding data while it is
being manipulated.

Organization of a microprocessor-
based system
I/O
Input / Output
Memory
ROM RAM
System Bus
ALU
Register
Array
Control
• Let’s expand the picture a bit.

Memory
• Memory stores information such as instructions
and data in binary format (0 and 1). It provides
this information to the microprocessor whenever
it is needed.
• Usually, there is a memory “sub-system” in a
microprocessor-based system. This sub-system
includes:
– The registers inside the microprocessor
– Read Only Memory (ROM)
• used to store information that does not change.
– Random Access Memory (RAM) (also known as
Read/Write Memory).
• used to store information supplied by the user. Such as
programs and data.

Memory Map and Addresses
FFFF
Address
Range
EPROM
RAM 1
RAM 2
RAM 3
RAM 4
• The memory map is a picture representation
of the address range and shows where the
different memory chips are located within
the address range.
0000 0000
8FFF
9000
A3FF
A400
Address Range of EPROM Chip
3FFF
4400
Address Range of 1st RAM Chip
5FFF
6000
Address Range of 2nd RAM Chip
Address Range of 3rd RAMChip
Address Range of 4th RAMChip
F7FF

Memory
• To execute a program:
– the user enters its instructions in binary format into the
memory.
– The microprocessor then reads these instructions and
whatever data is needed from memory, executes the
instructions and places the results either in memory or
produces it on an output device.

The three cycle instruction execution
model
• To execute a program, the microprocessor “reads”
each instruction from memory, “interprets” it, then
“executes” it.
• To use the right names for the cycles:
– The microprocessor fetches each instruction,
– decodes it,
– Then executes it.
• This sequence is continued until all instructions
are performed.

Machine Language
• The number of bits that form the “word” of a
microprocessor is fixed for that particular
processor.
– These bits define a maximum number of combinations.
• For example an 8-bit microprocessor can have at most 28 = 256
different combinations.
• However, in most microprocessors, not all of these
combinations are used.
– Certain patterns are chosen and assigned specific
meanings.
– Each of these patterns forms an instruction for the
microprocessor.
– The complete set of patterns makes up the
microprocessor’s machine language.

Hardwired Logic:
• A hardwired control unit has a processor that generates signals or
instructions to be implemented in correct sequence.
• This was the older method of control that works through the use of
distinct components, drums, a sequential circuit design, or flip chips.
• It is implemented using logic gates & flip flops. It is faster, less flexible
& limited in complexity.
32

Flexible Logic:
• A micro programmed control unit on the other hand makes use of a
micro sequencer from which instruction bits are decoded to be
implemented.
• It acts as the device supervisor that controls the rest of the
subsystems including arithmetic and logic units, registers, instruction
registers, off-chip input/output, and buses.
• It is slower, more flexible & greater complexity
33

Tri State Logic:
• Three-state logic is a logic used in electronic circuits wherein a third
state, the high-impedance state, is added to the original 1 and 0 logic
states that a port can be in.
• This high-impedance state effectively removes the port from the
circuit, as if it were not part of it.
• So in the third state of high impedance, the output from the port is
neither 1 nor 0, but rather the port does not appear to exist.Three-
state logic is also known as tri-state logic.
34

Bus structure
• There are three buses in Microprocessor:
• Address Bus
• Data Bus
• Control Bus
36

Address Bus
• Microprocessor has 16 bit address bus.
• The bus over which the CPU sends out the address of the memory
location is known as Address bus.
• The address bus carries the address of memory location to be written
or to be read from.
• The address bus is unidirectional. It means bits flowing occurs only in
one direction, only from microprocessor to peripheral devices.
• We can find that how much memory location it can using the formula
2^N. where N is the number of bits used for address lines.
37

Q. If a processor has 4 GB memory then how many address lines are
required to access this memory?
A.
38

Data Bus
• 8085 Microprocessor has 8 bit data bus. So it can be used to carry the
8 bit data starting from 00000000H(00H) to 11111111H(FFH).
• It is bidirectional. These lines are used for data flowing in both
direction means data can be transferred or can be received through
these lines.
• The data bus also connects the I/O ports and CPU. The largest
number that can appear on the data bus is 11111111.
It has 8 parallel lines of data bus.
• So it can access upto 2^8 = 256 data bus lines.
39

Control Bus
• The control bus is used for sending control signals to the memory and
I/O devices. The CPU sends control signal on the control bus to enable
the outputs of addressed memory devices or I/O port devices.
Some of the control bus signals are as follows:
• Memory read
• Memory write
• I/O read
• I/O write
40

SUMMARY
Introduction to Microprocessor
Internal organization
Basic concepts
41

FREQUENTLY ASKED QUESTIONS
• What is Bit ?
• What is byte?
• How many digits are there in Hexadecimal number system
• What is fixed logic?
• What is hardwired logic?
42

To make students understand
• Concepts of microprocessor
technology
• Inside microprocessor
43
LEARNING
OUTCOMES

ASSESSMENT PATTERN
44
A
Assignment
(each
assignment)
B
Time Bound
Surprise Test
(each test)
C
Quiz (each
quiz)
D
Mid Semester
Test(one per
test)
E
Homework
F
Discussion
Forums
G
Attendance
and
engagement
Score on BB
10 12 4 20 NA NA 2

Assessment Plan
INTERNAL
(40 MARKS)
Assignment
(10 marks)
Surprise test
(4 marks)
Mid term
exams
(20 marks)
Quiz
(4 marks)
ENGAGEMENT
TASK (HOMWORK
OR DISCUSSION
TASK)
Attendance
and
engagement
score on BB
( 2 marks)

REFERENCES
• Books: [1] Gaonkar, Ramesh. Microprocessor architecture, programming, and application with the 8085. Penram
International, 2002.
[2] Godse, Atul P., and Deepali A. Godse. Microprocessor and microcontroller. Technical publications, 2010.
[3] Kaushik, D. K. "An introduction to microprocessor 8085." New Delhi.: Dhan-pat Rai Publishing
Company 536 (2010).
• E-Books: [1] https://www.pdfdrive.com/understanding-80858086-microprocessors-and-peripheral-ics-
e17335339.html
• [2] https://www.pdfdrive.com/microprocessor-architecture-programming-and-applications-with-the-8085-
e176171206.html
• Websites: [1] https://nptel.ac.in/courses/108/107/108107029/
46

THANK YOU
For queries
Email: Bobbinpreet.ece@cumail.in

49
COURSE OBJECTIVES
S. No. Objectives
1
operations on them.
2
problems.
3
software systems.

50
COURSE OUTCOMES
microprocessor-pdf
CO
Number
Title Level
CO1
CO2
CO3
CO4
CO5

give results.
51
%20output.

SYLLABUS
Unit-I [15h]
• Chapter -1(Introduction)
• Review of Hardwired Logic v/s Flexible Logic, Tri State Logic.
Introduction to microprocessor, Difference between microprocessor
and microcomputer, Basic components of a microprocessor, system
bus: address, data and control buses.
• Chapter -2(8085 microprocessor)
• Architecture, pin diagram, flags, addressing modes, instruction set-
classification and applications, assembly language programming,
timing diagrams.
52

SYLLABUS
Unit-II [15h]
• Chapter -3 (Interfacing devices)
• Architecture, Block Diagram, Control words, Modes and working of8255.
• Chapter -4 (8085 Applications )
• Interfacing- Seven Segment LED display, Traffic control system.
53

SYLLABUS
Unit-III [15h]
• Chapter -5 (8086 Microprocessor)
• Architecture, block diagram and pin diagram of 8086, operating modes of 8086,
details of sub-blocks such as EU, BIU; memory segmentation and physical address
computations, program relocation, addressing modes.
• Chapter-6 (Advanced microprocessors)
• Introduction to 80186, 80286, 80386, 80486, Pentium microprocessors.
•
• ADVANCED TOPICS (BEYOND SYLLABUS)
• Design of interfacing circuits
54

Recommended Books
Text Books:
1. Gaonkar, Ramesh S., “Microprocessor Architecture, Programming &
Applications with 8085”, Wiley EasternLtd.
2. Ayala, “The 8086 Microprocessor: Programming & Interfacing the PC” ,
Cengage Learning.
Bhurchandi, K.M, Ray, A.K, “Advanced microprocessors and
peripherals”,TMH.
Reference Books:
1.Brey, “The Intel Microprocessors 8086- Pentium processor”,PHI.
2. Triebeland Singh, Avtar, “The 8088 & 8086 Microprocessors-Programming,
interfacing, Hardware & Applications”,PHI
55

What is microcomputer system ?
56

History of INTEL Microprocessor’s
57

58

59

60

Bus structure
• There are three buses in Microprocessor:
• Address Bus
• Data Bus
• Control Bus
62

Address Bus
• Microprocessor has 16 bit address bus.
• The bus over which the CPU sends out the address of the memory
location is known as Address bus.
• The address bus carries the address of memory location to be written
or to be read from.
• The address bus is unidirectional. It means bits flowing occurs only in
one direction, only from microprocessor to peripheral devices.
• We can find that how much memory location it can using the formula
2^N. where N is the number of bits used for address lines.
63

Q. If a processor has 4 GB memory then how many address lines are
required to access this memory?
A.
64

Data Bus
• 8085 Microprocessor has 8 bit data bus. So it can be used to carry the
8 bit data starting from 00000000H(00H) to 11111111H(FFH).
• It is bidirectional. These lines are used for data flowing in both
direction means data can be transferred or can be received through
these lines.
• The data bus also connects the I/O ports and CPU. The largest
number that can appear on the data bus is 11111111.
It has 8 parallel lines of data bus.
• So it can access upto 2^8 = 256 data bus lines.
65

Control Bus
• The control bus is used for sending control signals to the memory and
I/O devices. The CPU sends control signal on the control bus to enable
the outputs of addressed memory devices or I/O port devices.
Some of the control bus signals are as follows:
• Memory read
• Memory write
• I/O read
• I/O write
66

SUMMARY
Introduction to Microprocessor
Internal organization
Basic concepts
67

FREQUENTLY ASKED QUESTIONS
• What is Bit ?
• What is byte?
• How many digits are there in Hexadecimal number system
• What is fixed logic?
• What is hardwired logic?
68

To make students understand
• Concepts of microprocessor
technology
• Inside microprocessor
69
LEARNING
OUTCOMES

ASSESSMENT PATTERN
70
A
Assignment
(each
assignment)
B
Time Bound
Surprise Test
(each test)
C
Quiz (each
quiz)
D
Mid Semester
Test(one per
test)
E
Homework
F
Discussion
Forums
G
Attendance
and
engagement
Score on BB
10 12 4 20 NA NA 2

REFERENCES
• Books: [1] Gaonkar, Ramesh. Microprocessor architecture, programming, and application with the 8085. Penram
International, 2002.
[2] Godse, Atul P., and Deepali A. Godse. Microprocessor and microcontroller. Technical publications, 2010.
[3] Kaushik, D. K. "An introduction to microprocessor 8085." New Delhi.: Dhan-pat Rai Publishing
Company 536 (2010).
• E-Books: [1] https://www.pdfdrive.com/understanding-80858086-microprocessors-and-peripheral-ics-
e17335339.html
• [2] https://www.pdfdrive.com/microprocessor-architecture-programming-and-applications-with-the-8085-
e176171206.html
• Websites: [1] https://nptel.ac.in/courses/108/107/108107029/
72

THANK YOU
For queries
Email: mamtaarora.ece@cumail.in

ENGINEERING
By
Dr. Mamta Arora
TOPIC NAME: 8085 Architecture

75
COURSE OBJECTIVES
S. No. Objectives
1
operations on them.
2
problems.
3
software systems.

76
COURSE OUTCOMES
microprocessor-pdf
CO
Number
Title Level
CO1
CO2
CO3
CO4
CO5

give results.
77
%20output.

Architecture of 8085
Topics to be covered under Architecture of 8085 :
• Architecture
• Types of registers
 General purpose
 Flag registers
• Serial i/o control
• ALU
• Stack
5

Architecture of 8085
6
http://www.nptel.ac.in/courses/Webcourse-contents/IISc-
BANG/Microprocessors%20and%20Microcontrollers/pdf/Lecture_Notes/LNm1.pd

The 8085: CPU Internal Structure
6

Registers
• Six general purpose 8-bit registers: B, C, D, E, H, L
• They can also be combined as register pairs to perform 16-bit operations:
BC, DE, HL
• Registers are programmable (data load, move, etc.)
Accumulator
• Single 8-bit register that is part of the ALU !
• Used for arithmetic / logic operations – the result is always stored in the
accumulator.
8

Flag Bits
• Indicate the result of condition tests.
• Carry, Zero, Sign, Parity, etc.
• Conditional operations (IF / THEN) are executed based on the condition of these
flag bi
Program Counter (PC)
• Contains the memory address (16 bits) of the instruction that will be
executed in the next step.
8

Example 1:
• Let us consider the execution of the instruction ADD B. ADD is the mnemonic for addition. The
first operand is known to exist in the accumulator (Reg. A). Register B contains the second
operand. The meaning of the instruction is add the contents of the B register to the contents of A
register and store the result back in the accumulator (A). Symbolically we can write, (A) (A) + (B)
9

Stack Pointer (SP)
• The stack is a storage area of the processor. It consists of number of sequential
and RWM locations in which microprocessor saves the internal register contents
during subroutine calls and interrupts so that they will not be changed or
destroyed by a subroutine.
• 8085A µ𝑝 can address directly 64K memory locations. This is known as directly
addressable memory space starting from the address 0000H to FFFFH. This entire
memory area is usually divided by the user into program area, data area and stack
area. It is for the user to see that program area and data area do not overlap with
that of stack memory area. The size of the stack memory area depends upon the
application.
9

Working of 8085 microprocessor
https://www.youtube.com/watch?v=6pLlpKKky3M
Go through this link and watch the explanation for working of 8085
88

Topic that we have discussed today is architecture of 8085.In this we discussed role
of registers, flag register and stack.
89
Summary

. What do you understand by width of data bus .
. What is instruction set?
. What is program counter?
90
Frequently asked Questions

References
[1] http://microprocessorforyou.blogspot.in/2012/06/addressing-modes-in-8085.html
[2] http://scanftree.com/microprocessor/Addressing-Modes-In-8085
[3] http://www.editsworld.com/8085-addressing-modes-example-instruction-size/#.WF_JKtJ97IU
[4] http://www.eazynotes.com/notes/microprocessor/slides/addressing-modes-of-8085.pdf
[5]http://www.nptel.ac.in/courses/Webcourse-contents/IISc
BANG/Microprocessors%20and%20Microcontrollers/pdf/Lecture_Notes/LNm1.pdf
[6]https://www.google.co.in/search?q=general+registers+of+8085&espv=2&biw=1517&bih=735&sour
ce=lnms&tbm=isch&sa=X&ved=0ahUKEwiWmrritI_RAhWJpY8KHZ2xDPMQ_AUIBygC#imgrc=x_oqZ-
WUvBm1EM%3A
[8] http://www.eazynotes.com/notes/microprocessor/slides/introduction-to-microprocessors.pdf

BOOKS
1.Jan Holler, Vlasios Tsiatsis, Catherine Mulligan, Stefan Avesand, Stamatis
Karnouskos, David Boyle, “From Machine-to-Machine to the Internet of
Things: Introduction to a New Age of Intelligence”, 1st Edition, Academic
Press, 2014.
2. Vijay Madisetti and Arshdeep Bahga, “Internet of Things (A Hands-
onApproach)”, 1st Edition, VPT, 2014
Reference Books:
1. Microprocessor Architecture, Gaonkar, Ramesh S Wiley Eastern Ltd 2002
FIFTH Programming & Applications with 8085
92

ENGINEERING
By
Dr. Mamta Arora
TOPIC NAME: Registers

95
COURSE OBJECTIVES
S. No. Objectives
1
operations on them.
2
problems.
3
software systems.

96
COURSE OUTCOMES
microprocessor-pdf
CO
Number
Title Level
CO1
CO2
CO3
CO4
CO5

give results.
97
%20output.

Registers
• Accumulator or A register is an 8-bit register used for arithmetic,
logic, I/O and load/store operations.
• Flag Register has five 1-bit flags.
• Sign - set if the most significant bit of the result is set.
• Zero - set if the result is zero.
• Auxiliary carry - set if there was a carry out from bit 3 to bit 4 of the
result.
• Parity - set if the parity (the number of set bits in the result) is even.
98

Registers (cont..)
• Carry - set if there was a carry during addition, or borrow during
subtraction/comparison/rotation.
• General Registers :
 8-bit B and 8-bit C registers can be used as one 16-bit BC register
pair. When used as a pair the C register contains low-order byte.
Some instructions may use BC register as a data pointer.
8-bit D and 8-bit E registers can be used as one 16-bit DE register
pair. When used as a pair the E register contains low-order byte.
Some instructions may use DE register as a data pointer.
99

Registers (cont..)
• 8-bit H and 8-bit L registers can be used as one 16-bit HL register pair.
When used as a pair the L register contains low-order byte. HL
register usually contains a data pointer used to reference memory
addresses. In the instructions M refers HL pair.
• Stack pointer is a 16 bit register, points to the top of the stack. This
register is always decremented/incremented by 2 during push and
pop instructions.
• Program counter is a 16-bit register, points to the next instruction to
be executed.
100

Working of 8085 microprocessor
https://www.youtube.com/watch?v=6pLlpKKky3M
Go through this link and watch the explanation for working of 8085
105

Topic that we have discussed today is architecture of 8085.In this we discussed role
of registers, flag register and stack.
106
Summary

. What do you understand by width of data bus .
. What is instruction set?
. What is program counter?
107

BOOKS
Karnouskos, David Boyle, “From Machine-to-Machine to the Internet of
Things: Introduction to a New Age of Intelligence”, 1st Edition, Academic
Press, 2014.
2. Vijay Madisetti and Arshdeep Bahga, “Internet of Things (A Hands-
onApproach)”, 1st Edition, VPT, 2014
Reference Books:
1. Microprocessor Architecture, Gaonkar, Ramesh S Wiley Eastern Ltd 2002
FIFTH Programming & Applications with 8085
109

ENGINEERING
By
Bobbinpreet kaur
TOPIC NAME: Pin diagram of 8085

112
COURSE OBJECTIVES
S.
No.
Objectives
1
 To understand the architecture, components, flags and instruction set
of 8085 and8086.
 To design interfacing circuits using 8085 and8086.
To gain familiarity with 8255(PPI), 8253(Programmable interval timer),
8259 (PIC), 8237(DMA) and advanced microprocessor chips.
2
of 8085 and8086.
3
of 8085 and8086.

113
COURSE OUTCOMES
microprocessor-pdf
CO
Number
Title Level
CO1
Identify the basic element and functions of
microprocessor.
· Describe the architecture of microprocessor and its
peripheral devices
Rememb
er
CO2
Demonstrate fundamental understanding on the
operation between the microprocessor and its
interfacing devices.
Understa
nd
CO3
Apply the programming techniques in developing
the assembly language program for microprocessor
application.
Apply

Pin Diagram
Topics to be covered :
• 40-pin DIP (Dual in package) chip, based on NMOS technology.
5

Pin Configuration of Intel 8085A Microprocessor:
• The 8085A is an 8- bit microprocessor suitable for a wide range of application..
5
Fig. 1: http://www.nptel.ac.in/courses/Webcourse-contents/IISc-

A15 – A8 at pin no. 28 to pin no. 21:
• The microprocessor can address directly 2 16 memory locations or 65536
memory locations or 64k memory locations using 16- address lines (A15-A0).
Pin no. 28 to pin no. 21 give us the higher order 8-bits of the address (A15-A8).
These address lines are unidirectional, tri-state address lines.
• These address lines become tristated under three conditions namely:
(a) During DMA (direct memory access) operation.
(b) When a HALT instruction is executed.
(c) When microprocessor is being RESET.
5

AD7–AD0 at pin no. 19 to pin no. 12
• Pin no. 19 to pin no.12 marked AD7–AD0 are used for dual purpose. It is time
multiplexed lower 8-bit address bus (A7-A0) and 8- bit data bus (D7-D0).
Because at the time when this chip was developed, the practical limit on the
numbers of pins was 40. The only solution was to multiplex part of the address
bus with the data bus.
1. RESET STATE: (TRESET): Whenever microprocessor is reset, it enters in
reset state. The microprocessor can be in TRESET state for an integral multiple of
clock cycle.
2. WAIT STATE: It can be in this state for an integral number of clock cycles, the
duration being determined by an external content signal input marked READY.
3. HOLD STATE: (THOLD): As long as HOLD signal is active, microprocessor
is in HOLD state.
5

ALE at Pin No 30
• The 8085A uses a time multiplexed address-data bus. This is due to limited
number of pins on the 8085A. Low-order 8-bits of the address appear on the AD
bus during the first clock cycle i.e., T1 state of a machine cycle.
• It then becomes the data bus during the second and third clock cycles i.e., T2
and T3 states. ALE stands for address latch enable. It is used to distinguish
whether the AD7 – AD0 bus contains address bits A7 – A0 or data bits D7- D0.
It is a single pulse issued during every T1 state of the microprocessor
5

RD & WR Control signals at pin no 32 and at pin no
31:
• he BDB at pin no 19 to 12 are used for bi-directional data transfer operation
during T2 & T3 states. When the BDB is inputting the information from the
external world into the microprocessor, we say that 𝜇𝑝 is in READ mode and
operation is READ operation. When the 𝜇𝑝 is outputting 8-bit of information to
the external world through BDB we say 𝜇𝑝 is in WRITE mode and operation is
WRITE operation.
5

IO/M at pin no 34:
• IO/M is an output tri-state control signal. It is active both ways (HIGH as well
as LOW). Whenever the address issued by the 𝜇𝑝 on the address lines refers to
the memory then the 𝜇𝑝 makes IO/M LOW throughout T1,T2,T3,T4,T5 & T6
states of the machine cycle to indicate the external world that the address so
sent belongs to the memory and data on the BDB refers to the memory.
• Whenever the address on the address lines refers to an I/O device the 𝜇𝑝 makes
IO/M control signal output HIGH to tell the external world that the address on
the address bus refers to and I/O device and the data on the BDB refers to an
I/O device.
5

INTERRUPT CONTROL SIGNALS:
• TRAP at pin no. 6, RST7.5 at pin no. 7, RST6.5 at pin no. 8, RST 5.5 at pin no.
9, and INTR at pin no. 10 are interrupt control signals input provided for
interrupting the 𝜇𝑝 while it is executing the programmed.
• RST stands for RESTART. These interrupt control signal input can be broadly
divided in to two categories:
(a) Non – maskable interrupts
(b) Maskable interrupts
5

TRAP at pin no.6:
• TRAP control signal input of Intel 8085A processors is a non maskable (NMI)
RESTART vectored interrupt. When the power is ON, it is enabled and no
enable interrupt command is required. TRAP has the highest priority of any
interrupt.
• It is both rising edge and level sensitive interrupt i.e. it becomes active at the
Lo-Hi edge but must stay high until it is sampled and recognized.
• Whenever this interrupt is recognized, it forces the 8085A to perform a CALL
0024H instruction, means when the current instruction execution is over, the
program counter (PC) is loaded with 0024H so that the CPU starts executing the
program from 0024H.
5

INTR at pin no.10:
• This is the lowest priority interrupt request in the 8085A processor and is used
as a general purpose interrupt. An input of INTR=1 implies some external
device has put up an interrupt andwants the CPU to execute an appropriate
service routine. The 8085A monitors the status of the INTR line by sampling it
in the last but one clock cycle of each instruction and during HOLD & HALT
states.
• If the interrupt structure of the 8085A is enabled when INTR is sampled high,
the PC will not be incremented and an interrupt acknowledge signal (INTA = 0)
will be issued by the µ𝑝 in response to INTR. It is now the responsibility of the
interrupting device to issue a RESTART or CALL instruction so that the 8085A
can jump to the proper interrupt service subroutine. The INTR is enabled by
executing an EI instruction and is disabled by executing a DI instruction.
Disabled means INTR will not be acknowledged. It is also disabled by RESET
and immediately after an interrupt is acknowledged.
5

RST5.5, RST6.5 & RST7.5:
1. The RESTART instruction is automatically inserted by internal logic. It does not have to be
provided from outside. These
instructions are:
RST 5.5 identical to CALL 0020 H
Restart instructions are special 1-byte unconditional CALL instructions. The address for any RST
can be calculated multiplying the RST number with 8 and converting it into hexa. E.g. for RST5.5
the address is 5.5x8 = 44D = 002C H
2. RST7.5 is an edge (Low to High) sensitive interrupt unlike RST6.5, RST5.5 and INTR which
are level (High) triggered.
3. These three interrupts can be individually masked or unmasked using SIM instructions.
4. They have higher priority than INTR. Among them RST7.5 has the highest priority and RST5.5
has the lowest priority. Like the INTR, whenever any of these interrupts is recognized it
disables all the interrupts. These interrupts can be enabled/disabled using EI/DI instruction.
5

Status Signals S1 (33) and S0 (29):
5

HOLD at pin no 39 and HLDA at pin no 38:
• HOLD (Hold) is a control signal input and HLDA (Hold acknowledge) is a
control signal output. These two signals are used for hand shaked control during
DMA operation (Direct Memory Access).
5

• Have covered
• The various pins of 8085
• What the modes of pins and working state.
130
Summary

• To be surely sensed, in 8085, INTR must be high for number of T-states equal to?
• What is the function of ready pin in 8085?
• What is the function of hold pin?
131

References
[1] http://microprocessorforyou.blogspot.in/2012/06/addressing-modes-in-8085.html
[2] http://scanftree.com/microprocessor/Addressing-Modes-In-8085
[3] http://www.editsworld.com/8085-addressing-modes-example-instruction-size/#.WF_JKtJ97IU
[4] http://www.eazynotes.com/notes/microprocessor/slides/addressing-modes-of-8085.pdf
[5]http://www.nptel.ac.in/courses/Webcourse-contents/IISc
[6]https://www.google.co.in/search?q=general+registers+of+8085&espv=2&biw=1517&bih=735&sour
ce=lnms&tbm=isch&sa=X&ved=0ahUKEwiWmrritI_RAhWJpY8KHZ2xDPMQ_AUIBygC#imgrc=x_oqZ-
WUvBm1EM%3A
[7] http://www.eazynotes.com/notes/microprocessor/slides/introduction-to-microprocessors.pdf

BOOKS
Karnouskos, David Boyle, “From Machine-to-Machine to the Internet of Things:
Introduction to a New Age of Intelligence”, 1st Edition, Academic Press, 2014.
2. Vijay Madisetti and Arshdeep Bahga, “Internet of Things (A Hands-onApproach)”,
1st Edition, VPT, 2014
Reference Books:
1. Microprocessor Architecture, Gaonkar, Ramesh S Wiley Eastern Ltd 2002 FIFTH
Programming & Applications with 8085
133

mICROPROCESSOR UNIT 1 ALL.pptx

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