SlideShare a Scribd company logo
Microprocessor and Micro Controller
Unit I
Microprocessor Architecture and its Operation
Prepared By
Dr. S.Murugan, Associate Professor
Department of Computer Science,
AlagappaGovernment Arts College, Karaikudi.
(Affiliated by AlagappaUniversity)
Mailid: muruganjit@gmail.com
Reference Book:
Microprocessor Architecture – Programming and Applications with 8085 – R. S. Gaonkar
Introduction - Microprocessor Architecture and
its Operation
Microprocessor
➢ The microprocessor is a programmable digital device,
designed with registers, flip-flops and timing element.
➢ It is a central processing unit (CPU) on a single
integrated circuit (IC) chip that performs arithmetic
and logic operations, data transfer, and control
operations.
➢ It acts as the brain of a computer or embedded system.
Microprocessor architecture
➢ Microprocessor architecture refers to the internal
structure and organization of components in a
microprocessor, including its registers, buses,
instruction set, and control unit, which collectively
determine how it processes data.
➢ The function of microprocessor can be classified into
three general categories;
(i) Microprocessor-initiated operations
(ii) internal operations
(iii) peripheral operations.
Microprocessor architecture
➢ To perform the above functions, the microprocessor
requires a group of logic circuits and a set of signals
called control signal.
➢ A control signal is an electrical signal generated by
the control unit of a microprocessor or computer
system to coordinate and control the operation of other
components, such as memory, input/output devices,
and the processor itself.
Microprocessor architecture
➢ The Central Processing Unit (CPU) and the Micro
Processor Unit (MPU) is related but not same. A CPU
can be implemented as a combination of more than
one chip.
➢ Whereas, the MPU refers a single chip processor. The
microprocessor and Micro Processor Unit often are
used synonymously.
Microprocessor initiated operations and Bus
Organization
Microprocessor initiated operations
➢ Microprocessor-initiated operations are tasks performed
by the microprocessor to communicate with memory and
peripherals, such as memory read, memory write, I/O read,
and I/O write operations.
➢ The MPU performs primarily four operations :
1. Memory Read : Reads data or instructions from memory.
2. Memory Write : Write data or instructions into memory.
3. I/O Read : Accepts data from input devices.
4. I/O Write : Sends data to output devices.
Microprocessor initiated operations
➢ To communicate with a peripheral or a memory
location, the MPU needs to perform the following
steps:
1. Identify the peripheral or the memory location (with
its address)
2. Transfer binary information (data and instruction)
3. Provide timing or synchronization signals.
The 8085 MPU performs these functions using three
sets of communication lines called buses: the address
bus, the data bus, and the control bus.
8085 Bus Organization
➢ The 8085 bus organization refers to the system of
buses used by the 8085 microprocessor to
communicate with memory, input/output devices,
and other components as shown in Figure 1.1.
➢ The 8085 microprocessor has three primary buses:
Address Bus, Data Bus, and Control Bus, each
serving a specific purpose in the microprocessor's
operation.
8085 Bus Organization
Fig. 1.1 The 8085 Bus Structure
Address Bus
➢ The address bus is a group of 16 lines generally
identified as A0 to A15.
➢ It is unidirectional (bits flow in one direction) from the
microprocessor to the memory or peripheral devices.
➢ The MPU uses the address bus to specify the memory
location or I/O device to be accessed.
➢ In the 8085 microprocessors, the address is 16 bits,
allowing access to 216=65,536 (64 KB) memory
locations.
Address Bus
Data Bus
➢ The data bus is a group of 8 lines generally identified
as D0 to D7.
➢ It is bi-directional (bits flow in both direction)
between the microprocessor and the memory or
peripheral devices.
➢ The data bus is used to transfer data between the
processor, memory, and I/O devices.
➢ The eight data lines enable the MPU to manipulate 8-
bit data ranging from 00 to FF (28 =256).
Data Bus
➢ The smallest number that can appear on the data bus
0000 0000 (00).
➢ The largest number that can appear on the data bus
1111 1111 (FF).
➢ so that the 8085 is known as an 8-bit microprocessor
Difference between Data Bus and Address Bus
S. No.Feature Data Bus Address Bus
1. Direction Bidirectional Unidirectional
2.
Purpose
Transfers data or
instructions
Carries memory/I/O
addresses
3. Size
(8085)
8 bits 16 bits
4 Functional
ity
Exchanges data
between components
Identifies memory or
I/O locations
Control Bus
➢ The control bus is comprised of various single lines
that carry synchronization signals.
➢ It is used to provide the timing or synchronization
signals.
➢ The control bus lines are not a group of lines like
address bus or data bus, the individual lines that
provide a pulse to indicate an MPU operation.
➢ The MPU generates control signals for every
operation (such as memory read or memory write
operations).
Control Bus
➢ The control bus carries control signals to coordinate
and manage communication between the processor,
memory, and peripherals. Important control signals
include:
o RD (Read): Indicates data is being read.
o WR (Write): Indicates data is being written.
o ALE (Address Latch Enable): Distinguishes
address and data on the same lines.
o IO/M: Differentiates memory and I/O operations.
The control bus ensures proper synchronization
during data transfer.
Control Bus - Example
➢ For Example the following instruction, the data 78 is
transferred into Register B.
2000 06 MVI B,78H
➢ Here 2000 is a memory location, 06 is a hex code for
immediate data transfer to Register B.
Fig. 1.2 Memory Read Operation
Control Bus - Example
➢ The following sequence of steps to be followed to read
an instruction from a memory location as shown in Fig
1.2.
1. 16 -bit address (2000) placed on the address bus.
2. The address is decoded by external logic circuit and
the memory location is identified.
3. MPU sends the memory read control signal (pulse).
4. The pulse activates the memory chip.
5. The contents of the memory location (8-bit data – 06)
placed on the data bus and brought inside the MPU.
Internal Data Operations and the 8085 Registers
Internal Data Operations
➢ Internal data operation in the 8085 microprocessor
refers to operations that manipulate data within the
microprocessor, using its internal registers and the
accumulator.
➢ These operations include arithmetic, logical, and data
transfer instructions that involve temporary storage
and processing without external memory access. For
example, adding two numbers, performing a logical
AND operation, or moving data between registers.
The accumulator and general-purpose registers are
primarily involved in these operations.
Internal Data Operations
➢ The internal architecture of the 8085 microprocessor
determines how and what operations can be performed
with the data. These operations are
➢ Store 8-bit data
➢ Perform arithmetic and logical operations.
➢ Test for conditions (Carry Flag).
➢ Sequence the execution of instructions
(Program Counter)
➢ Store data temporarily during execution in the
defined R/W memory locations called the stack.
8085 Registers
➢ To perform the above operations, the microprocessor
requires registers, an arithmetic/logic unit (ALU) ,
control logic and internal buses.
➢ The programming model of the 8085 displaying the
internal registers and accumulator as shown in the
figure 1.3.
Fig. 1.3 The 8085 Programmable Registers
8085 Registers
➢ The 8085 microprocessor has several programmable
registers that perform specific functions in data
handling and processing.
➢ Here's a concise explanation of each component:
➢ Accumulator (A): Stores results of arithmetic,
logical operations, and intermediate data.
➢ General Purpose Registers (B, C, D, E, H, L):
Used for temporary storage of data during
operations.
➢ Flag Register: Contains status flags (Z, S, P, CY,
AC) indicating conditions after operations.
8085 Registers
➢ Program Counter (PC): Holds the address of the
next instruction to be executed.
➢ Stack Pointer (SP): Points to the top of the stack,
used for subroutine calls and returns.
➢ Instruction Register (IR): Holds the current
instruction being decoded and executed.
➢ Temporary Register: Holds intermediate data
during execution, typically used for internal
operations.
Microprocessor function - Example program
➢ The following example program (addition of two
numbers) demonstrates the function of the
microprocessor.
➢ The hex codes of the program are stored in memory
locations from 2000 to 2005 as shown in Fig. 1.2.
Microprocessor function with Example program
Memory
Location
Hex
Code
Mnemonics Comments
2000 06 MVI B, 78H ; Transfer the value 78 into Register B.
2001 78
2002 3E MVI A, F2H ; Transfer the value F2 to Accumulator.
2003 F2
2004 80 ADD B ; The content of Register B is added with
Accumulator and the results are stored in
Accumulator.
2005 76 HLT ; Terminate the Program
Microprocessor function with Example program
➢ When executes the above instructions, the
microprocessor places the address 2000 into address
bus and increments the address in the PC (Program
Counter) to 2001 for the next operation. It brings the
code 06, interprets the code, places the address 2001
on the address bus, and then gets byte 78H and
increments the address in PC to 2002.
➢ The First two instruction is used to transfer the data
into register B and Register A.
Microprocessor function with Example program
➢ The third instruction ADD is used to perform the
addition operation and the result is stored into
accumulator. In this case 78 + F2 = 16AH, the
accumulator holds only the value 6A, the value 1
indicates the carry flag.
➢ The Fourth instruction terminates the program.
Peripheral or Externally Initiated Operation
➢ External devices can initiate the following operations :
Reset, Interrupt, Ready and Hold.
➢ Reset : When the reset pin is activated by external key
(reset key), all internal operations are suspended and
the program counter is cleared. Now, the program
execution can begin at the zero memory address.
➢ Interrupt : The microprocessor can be interrupted
from the normal execution of instructions and asked to
execute some other instructions called a service
routine. The microprocessor resumes its operation
after completing the service routine.
Peripheral or Externally Initiated Operation
➢ Ready : If the signal of this ready pin is low, the
microprocessor enters into a wait state.If it is high, the
microprocessor ready to send or receive data.
➢ Hold : When the HOLD pin is activated by an
external signal, the microprocessor relinquishes
control of buses and allows the external peripherals to
use them. For example, the HOLD signal is used in
Direct Memory Access (DMA) data transfer.
Difference between Microprocessor-initiated
operation and Peripheral-Initiated Operation
Feature Microprocessor-Initiated Peripheral-Initiated
Initiator Microprocessor External device (peripheral)
Examples
Memory Read, Memory
Write, I/O Read
Interrupts, Direct Memory
Access (DMA)
Control
Controlled by
microprocessor signals
Triggered by external signals
Priority Sequentially executed Can interrupt current operations
Execution
Part of the microprocessor
program flow
Requires special handling like
ISR

More Related Content

PDF
Z80 microprocessor architecture1
PPTX
Business Law PPt.pptx
PDF
Lecture Notes - Introduction to Computer Network
PPT
Microprocessor
PDF
Lecture Notes Unit III The DataLink Layer
PPTX
Energy Meters
PPTX
3.programmable interrupt controller 8259
PPT
Voltage Regulators ppt
Z80 microprocessor architecture1
Business Law PPt.pptx
Lecture Notes - Introduction to Computer Network
Microprocessor
Lecture Notes Unit III The DataLink Layer
Energy Meters
3.programmable interrupt controller 8259
Voltage Regulators ppt

What's hot (20)

PDF
Lecture Notes Microprocessor and Controller Unit2
PPT
Computer organisation Module 1.ppt
PDF
PPT
input output Organization
DOC
Microprocessor and Microcontroller Anna University Answer Key April / May - 2015
PPTX
programming techniques
PDF
Chapter 2-8085 Microprocessor Architecture and Microcomputer Systems
PPTX
1. Introduction to Microprocessor.pptx
PPTX
memory organi.pptx
PPT
Instruction set-of-8085
PPTX
80386 Architecture
PPTX
29. 8086 microprocessor pin diagram
PPT
Bus and Memory transfer
PPS
Addressing modes of 8085
PPT
Addressing modes (detailed data path)
PPTX
Presentation on 8086 microprocessor
PPTX
Timing Diagram.pptx
PPT
Basic MIPS implementation
PPTX
Register transfer language & its micro operations
PPT
Modes Of Transfer in Input/Output Organization
Lecture Notes Microprocessor and Controller Unit2
Computer organisation Module 1.ppt
input output Organization
Microprocessor and Microcontroller Anna University Answer Key April / May - 2015
programming techniques
Chapter 2-8085 Microprocessor Architecture and Microcomputer Systems
1. Introduction to Microprocessor.pptx
memory organi.pptx
Instruction set-of-8085
80386 Architecture
29. 8086 microprocessor pin diagram
Bus and Memory transfer
Addressing modes of 8085
Addressing modes (detailed data path)
Presentation on 8086 microprocessor
Timing Diagram.pptx
Basic MIPS implementation
Register transfer language & its micro operations
Modes Of Transfer in Input/Output Organization
Ad

Similar to Lecture Notes - Microprocessor - Unit 1 - Microprocessor Architecture and its operation (20)

PPTX
co-6.pptx mca ist sem computer organization
PPTX
8085microprocessor-functional block diagram, Arithmetic Logic Unit (ALU), Tim...
PPTX
8085 microprocessor
PDF
MPMC all units .pdf
PPTX
Introduction of CPU part 2
PPT
architect.ppt
PDF
Overview of microcontroller and microprocessor
PDF
MICROPROCESSOR 8085 WITH PROGRAMS
PDF
Computer engineering - overview of microprocessors
PDF
MPMC UNIT-1. Microprocessor 8085 pdf Microprocessor and Microcontroller
PPTX
Microprocessor and Microcontroller.pptx
PPT
architecture memory interfacing
PDF
Mpmc unit 1 notes
PDF
U proc ovw
PPTX
MICROPROCESSOR SYSTEM AND INTERFACING.pptx
PPTX
8085 MICROPROCESSOR ARCHITECTURE AND ITS OPERATIONS
PDF
8085_microprocessor_all_universities_syllabus
PDF
EE8551 MPMC
PDF
20838382 microprocessor-8085-notes
PPTX
Mechatronics ME8791
co-6.pptx mca ist sem computer organization
8085microprocessor-functional block diagram, Arithmetic Logic Unit (ALU), Tim...
8085 microprocessor
MPMC all units .pdf
Introduction of CPU part 2
architect.ppt
Overview of microcontroller and microprocessor
MICROPROCESSOR 8085 WITH PROGRAMS
Computer engineering - overview of microprocessors
MPMC UNIT-1. Microprocessor 8085 pdf Microprocessor and Microcontroller
Microprocessor and Microcontroller.pptx
architecture memory interfacing
Mpmc unit 1 notes
U proc ovw
MICROPROCESSOR SYSTEM AND INTERFACING.pptx
8085 MICROPROCESSOR ARCHITECTURE AND ITS OPERATIONS
8085_microprocessor_all_universities_syllabus
EE8551 MPMC
20838382 microprocessor-8085-notes
Mechatronics ME8791
Ad

More from Murugan146644 (18)

PDF
Computer Network Unit IV - Lecture Notes - Network Layer
PDF
Assembly Language Program for 16_bit_Addition
PDF
Lecture Notes Unit III PArt 2 - The DataLink Layer Medium Access Control Subl...
PDF
Lecture Notes - Unit II - The Physical Layer
PDF
Lecture Notes Unit3 chapter22 - distributed databases
PDF
Lecture Notes Unit3 chapter21 - parallel databases
PDF
Lecture Notes Unit3 chapter20 - Database System Architectures
PDF
Relational Database Management System (RDBMS) LAB - GROUP B
PDF
Relational Database Managment System Lab - Group A
PDF
Lecture Notes Unit2 chapter7 RelationalDatabaseDesign
PDF
Lecture Notes Unit 1 chapter 6 E-R MODEL
PDF
Lecture Notes Unit1 chapter1 Introduction
PDF
Lecture Notes Unit5 chapter19 Cursor in Pl/SQL
PDF
Lecture Notes Unit5 chapter18 Packages.pdf
PDF
Lecture Notes Unit5 chapter17 Stored procedures and functions
PDF
Lecture Notes Unit5 chapter16 Trigger Creation
PDF
Lecture Notes Unit5 chapter 15 PL/SQL Programming
PDF
Lecture Notes Unit4 Chapter13 users , roles and privileges
Computer Network Unit IV - Lecture Notes - Network Layer
Assembly Language Program for 16_bit_Addition
Lecture Notes Unit III PArt 2 - The DataLink Layer Medium Access Control Subl...
Lecture Notes - Unit II - The Physical Layer
Lecture Notes Unit3 chapter22 - distributed databases
Lecture Notes Unit3 chapter21 - parallel databases
Lecture Notes Unit3 chapter20 - Database System Architectures
Relational Database Management System (RDBMS) LAB - GROUP B
Relational Database Managment System Lab - Group A
Lecture Notes Unit2 chapter7 RelationalDatabaseDesign
Lecture Notes Unit 1 chapter 6 E-R MODEL
Lecture Notes Unit1 chapter1 Introduction
Lecture Notes Unit5 chapter19 Cursor in Pl/SQL
Lecture Notes Unit5 chapter18 Packages.pdf
Lecture Notes Unit5 chapter17 Stored procedures and functions
Lecture Notes Unit5 chapter16 Trigger Creation
Lecture Notes Unit5 chapter 15 PL/SQL Programming
Lecture Notes Unit4 Chapter13 users , roles and privileges

Recently uploaded (20)

PDF
Empowerment Technology for Senior High School Guide
PPTX
TNA_Presentation-1-Final(SAVE)) (1).pptx
PDF
advance database management system book.pdf
PPTX
CHAPTER IV. MAN AND BIOSPHERE AND ITS TOTALITY.pptx
PDF
medical_surgical_nursing_10th_edition_ignatavicius_TEST_BANK_pdf.pdf
PDF
BP 704 T. NOVEL DRUG DELIVERY SYSTEMS (UNIT 2).pdf
PPTX
Chinmaya Tiranga Azadi Quiz (Class 7-8 )
PPTX
Share_Module_2_Power_conflict_and_negotiation.pptx
PDF
Τίμαιος είναι φιλοσοφικός διάλογος του Πλάτωνα
PDF
LDMMIA Reiki Yoga Finals Review Spring Summer
PPTX
Introduction to pro and eukaryotes and differences.pptx
PDF
What if we spent less time fighting change, and more time building what’s rig...
PDF
FOISHS ANNUAL IMPLEMENTATION PLAN 2025.pdf
PDF
Vision Prelims GS PYQ Analysis 2011-2022 www.upscpdf.com.pdf
PDF
ChatGPT for Dummies - Pam Baker Ccesa007.pdf
PDF
Practical Manual AGRO-233 Principles and Practices of Natural Farming
PDF
Chinmaya Tiranga quiz Grand Finale.pdf
PDF
A GUIDE TO GENETICS FOR UNDERGRADUATE MEDICAL STUDENTS
PDF
Hazard Identification & Risk Assessment .pdf
PDF
Weekly quiz Compilation Jan -July 25.pdf
Empowerment Technology for Senior High School Guide
TNA_Presentation-1-Final(SAVE)) (1).pptx
advance database management system book.pdf
CHAPTER IV. MAN AND BIOSPHERE AND ITS TOTALITY.pptx
medical_surgical_nursing_10th_edition_ignatavicius_TEST_BANK_pdf.pdf
BP 704 T. NOVEL DRUG DELIVERY SYSTEMS (UNIT 2).pdf
Chinmaya Tiranga Azadi Quiz (Class 7-8 )
Share_Module_2_Power_conflict_and_negotiation.pptx
Τίμαιος είναι φιλοσοφικός διάλογος του Πλάτωνα
LDMMIA Reiki Yoga Finals Review Spring Summer
Introduction to pro and eukaryotes and differences.pptx
What if we spent less time fighting change, and more time building what’s rig...
FOISHS ANNUAL IMPLEMENTATION PLAN 2025.pdf
Vision Prelims GS PYQ Analysis 2011-2022 www.upscpdf.com.pdf
ChatGPT for Dummies - Pam Baker Ccesa007.pdf
Practical Manual AGRO-233 Principles and Practices of Natural Farming
Chinmaya Tiranga quiz Grand Finale.pdf
A GUIDE TO GENETICS FOR UNDERGRADUATE MEDICAL STUDENTS
Hazard Identification & Risk Assessment .pdf
Weekly quiz Compilation Jan -July 25.pdf

Lecture Notes - Microprocessor - Unit 1 - Microprocessor Architecture and its operation

  • 1. Microprocessor and Micro Controller Unit I Microprocessor Architecture and its Operation Prepared By Dr. S.Murugan, Associate Professor Department of Computer Science, AlagappaGovernment Arts College, Karaikudi. (Affiliated by AlagappaUniversity) Mailid: [email protected] Reference Book: Microprocessor Architecture – Programming and Applications with 8085 – R. S. Gaonkar
  • 2. Introduction - Microprocessor Architecture and its Operation
  • 3. Microprocessor ➢ The microprocessor is a programmable digital device, designed with registers, flip-flops and timing element. ➢ It is a central processing unit (CPU) on a single integrated circuit (IC) chip that performs arithmetic and logic operations, data transfer, and control operations. ➢ It acts as the brain of a computer or embedded system.
  • 4. Microprocessor architecture ➢ Microprocessor architecture refers to the internal structure and organization of components in a microprocessor, including its registers, buses, instruction set, and control unit, which collectively determine how it processes data. ➢ The function of microprocessor can be classified into three general categories; (i) Microprocessor-initiated operations (ii) internal operations (iii) peripheral operations.
  • 5. Microprocessor architecture ➢ To perform the above functions, the microprocessor requires a group of logic circuits and a set of signals called control signal. ➢ A control signal is an electrical signal generated by the control unit of a microprocessor or computer system to coordinate and control the operation of other components, such as memory, input/output devices, and the processor itself.
  • 6. Microprocessor architecture ➢ The Central Processing Unit (CPU) and the Micro Processor Unit (MPU) is related but not same. A CPU can be implemented as a combination of more than one chip. ➢ Whereas, the MPU refers a single chip processor. The microprocessor and Micro Processor Unit often are used synonymously.
  • 7. Microprocessor initiated operations and Bus Organization
  • 8. Microprocessor initiated operations ➢ Microprocessor-initiated operations are tasks performed by the microprocessor to communicate with memory and peripherals, such as memory read, memory write, I/O read, and I/O write operations. ➢ The MPU performs primarily four operations : 1. Memory Read : Reads data or instructions from memory. 2. Memory Write : Write data or instructions into memory. 3. I/O Read : Accepts data from input devices. 4. I/O Write : Sends data to output devices.
  • 9. Microprocessor initiated operations ➢ To communicate with a peripheral or a memory location, the MPU needs to perform the following steps: 1. Identify the peripheral or the memory location (with its address) 2. Transfer binary information (data and instruction) 3. Provide timing or synchronization signals. The 8085 MPU performs these functions using three sets of communication lines called buses: the address bus, the data bus, and the control bus.
  • 10. 8085 Bus Organization ➢ The 8085 bus organization refers to the system of buses used by the 8085 microprocessor to communicate with memory, input/output devices, and other components as shown in Figure 1.1. ➢ The 8085 microprocessor has three primary buses: Address Bus, Data Bus, and Control Bus, each serving a specific purpose in the microprocessor's operation.
  • 11. 8085 Bus Organization Fig. 1.1 The 8085 Bus Structure
  • 12. Address Bus ➢ The address bus is a group of 16 lines generally identified as A0 to A15. ➢ It is unidirectional (bits flow in one direction) from the microprocessor to the memory or peripheral devices. ➢ The MPU uses the address bus to specify the memory location or I/O device to be accessed. ➢ In the 8085 microprocessors, the address is 16 bits, allowing access to 216=65,536 (64 KB) memory locations.
  • 14. Data Bus ➢ The data bus is a group of 8 lines generally identified as D0 to D7. ➢ It is bi-directional (bits flow in both direction) between the microprocessor and the memory or peripheral devices. ➢ The data bus is used to transfer data between the processor, memory, and I/O devices. ➢ The eight data lines enable the MPU to manipulate 8- bit data ranging from 00 to FF (28 =256).
  • 15. Data Bus ➢ The smallest number that can appear on the data bus 0000 0000 (00). ➢ The largest number that can appear on the data bus 1111 1111 (FF). ➢ so that the 8085 is known as an 8-bit microprocessor
  • 16. Difference between Data Bus and Address Bus S. No.Feature Data Bus Address Bus 1. Direction Bidirectional Unidirectional 2. Purpose Transfers data or instructions Carries memory/I/O addresses 3. Size (8085) 8 bits 16 bits 4 Functional ity Exchanges data between components Identifies memory or I/O locations
  • 17. Control Bus ➢ The control bus is comprised of various single lines that carry synchronization signals. ➢ It is used to provide the timing or synchronization signals. ➢ The control bus lines are not a group of lines like address bus or data bus, the individual lines that provide a pulse to indicate an MPU operation. ➢ The MPU generates control signals for every operation (such as memory read or memory write operations).
  • 18. Control Bus ➢ The control bus carries control signals to coordinate and manage communication between the processor, memory, and peripherals. Important control signals include: o RD (Read): Indicates data is being read. o WR (Write): Indicates data is being written. o ALE (Address Latch Enable): Distinguishes address and data on the same lines. o IO/M: Differentiates memory and I/O operations. The control bus ensures proper synchronization during data transfer.
  • 19. Control Bus - Example ➢ For Example the following instruction, the data 78 is transferred into Register B. 2000 06 MVI B,78H ➢ Here 2000 is a memory location, 06 is a hex code for immediate data transfer to Register B. Fig. 1.2 Memory Read Operation
  • 20. Control Bus - Example ➢ The following sequence of steps to be followed to read an instruction from a memory location as shown in Fig 1.2. 1. 16 -bit address (2000) placed on the address bus. 2. The address is decoded by external logic circuit and the memory location is identified. 3. MPU sends the memory read control signal (pulse). 4. The pulse activates the memory chip. 5. The contents of the memory location (8-bit data – 06) placed on the data bus and brought inside the MPU.
  • 21. Internal Data Operations and the 8085 Registers
  • 22. Internal Data Operations ➢ Internal data operation in the 8085 microprocessor refers to operations that manipulate data within the microprocessor, using its internal registers and the accumulator. ➢ These operations include arithmetic, logical, and data transfer instructions that involve temporary storage and processing without external memory access. For example, adding two numbers, performing a logical AND operation, or moving data between registers. The accumulator and general-purpose registers are primarily involved in these operations.
  • 23. Internal Data Operations ➢ The internal architecture of the 8085 microprocessor determines how and what operations can be performed with the data. These operations are ➢ Store 8-bit data ➢ Perform arithmetic and logical operations. ➢ Test for conditions (Carry Flag). ➢ Sequence the execution of instructions (Program Counter) ➢ Store data temporarily during execution in the defined R/W memory locations called the stack.
  • 24. 8085 Registers ➢ To perform the above operations, the microprocessor requires registers, an arithmetic/logic unit (ALU) , control logic and internal buses. ➢ The programming model of the 8085 displaying the internal registers and accumulator as shown in the figure 1.3. Fig. 1.3 The 8085 Programmable Registers
  • 25. 8085 Registers ➢ The 8085 microprocessor has several programmable registers that perform specific functions in data handling and processing. ➢ Here's a concise explanation of each component: ➢ Accumulator (A): Stores results of arithmetic, logical operations, and intermediate data. ➢ General Purpose Registers (B, C, D, E, H, L): Used for temporary storage of data during operations. ➢ Flag Register: Contains status flags (Z, S, P, CY, AC) indicating conditions after operations.
  • 26. 8085 Registers ➢ Program Counter (PC): Holds the address of the next instruction to be executed. ➢ Stack Pointer (SP): Points to the top of the stack, used for subroutine calls and returns. ➢ Instruction Register (IR): Holds the current instruction being decoded and executed. ➢ Temporary Register: Holds intermediate data during execution, typically used for internal operations.
  • 27. Microprocessor function - Example program ➢ The following example program (addition of two numbers) demonstrates the function of the microprocessor. ➢ The hex codes of the program are stored in memory locations from 2000 to 2005 as shown in Fig. 1.2.
  • 28. Microprocessor function with Example program Memory Location Hex Code Mnemonics Comments 2000 06 MVI B, 78H ; Transfer the value 78 into Register B. 2001 78 2002 3E MVI A, F2H ; Transfer the value F2 to Accumulator. 2003 F2 2004 80 ADD B ; The content of Register B is added with Accumulator and the results are stored in Accumulator. 2005 76 HLT ; Terminate the Program
  • 29. Microprocessor function with Example program ➢ When executes the above instructions, the microprocessor places the address 2000 into address bus and increments the address in the PC (Program Counter) to 2001 for the next operation. It brings the code 06, interprets the code, places the address 2001 on the address bus, and then gets byte 78H and increments the address in PC to 2002. ➢ The First two instruction is used to transfer the data into register B and Register A.
  • 30. Microprocessor function with Example program ➢ The third instruction ADD is used to perform the addition operation and the result is stored into accumulator. In this case 78 + F2 = 16AH, the accumulator holds only the value 6A, the value 1 indicates the carry flag. ➢ The Fourth instruction terminates the program.
  • 31. Peripheral or Externally Initiated Operation ➢ External devices can initiate the following operations : Reset, Interrupt, Ready and Hold. ➢ Reset : When the reset pin is activated by external key (reset key), all internal operations are suspended and the program counter is cleared. Now, the program execution can begin at the zero memory address. ➢ Interrupt : The microprocessor can be interrupted from the normal execution of instructions and asked to execute some other instructions called a service routine. The microprocessor resumes its operation after completing the service routine.
  • 32. Peripheral or Externally Initiated Operation ➢ Ready : If the signal of this ready pin is low, the microprocessor enters into a wait state.If it is high, the microprocessor ready to send or receive data. ➢ Hold : When the HOLD pin is activated by an external signal, the microprocessor relinquishes control of buses and allows the external peripherals to use them. For example, the HOLD signal is used in Direct Memory Access (DMA) data transfer.
  • 33. Difference between Microprocessor-initiated operation and Peripheral-Initiated Operation Feature Microprocessor-Initiated Peripheral-Initiated Initiator Microprocessor External device (peripheral) Examples Memory Read, Memory Write, I/O Read Interrupts, Direct Memory Access (DMA) Control Controlled by microprocessor signals Triggered by external signals Priority Sequentially executed Can interrupt current operations Execution Part of the microprocessor program flow Requires special handling like ISR