8085 Microprocessor Addressing Modes and Instructions, Lecture notes of Microcontrollers

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MICRO-PROCESSOR AND

MICROCONTROLLERS

( EC1506)

DR. Jayendra Kumar

Deptt. Of ECE, NIT Jamshedpur

Introduction to Microprocessors

• Definition:

Microprocessor is the controlling unit or CPU of a

micro-computer, fabricated on a very small chip

capable of performing arithmetic and logical

operations and communicating with the external

devices connected to it.

A Computer

• A computer has the following

units:

• Input Unit
• Output Unit
• Memory Unit
• Central Processing Unit

A Computer

• ARITHMETIC AND LOGIC UNIT (ALU)
  • This unit perform all the logical and arithmetic operations.
  • Various arithmetic operations are: addition, subtraction, increment and decrement etc.
  • Various logical operations are: AND, OR, NOT, XOR, etc.
• TIMING AND CONTROL UNIT
  • This unit controls the entire operations being performed by the system.
  • It controls the operations of ALU, input/output devices and memory unit.
  • This unit interprets the instructions and generates various timing and control signals.
• REGISTERS
  • A register is a very small amount of very fast memory that is built into the CPU in order to store the current data and instructions which are being executed by the CPU.

A Micro-Computer

• As the name implies, microcomputers are

small computers.

• The block diagram of the microcomputer is

similar to the computer except that the

central processing unit of the microcomputer

is contained in a single IC called the

microprocessor.

A Micro-Computer

• A microprocessor is a LSI (Large Scale Integration) IC

that does almost all the functions of the CPU.

• It is also defined as a CPU contained in a single chip.
• The basic function of the microprocessor is:
  • to fetch the instructions stored in the main memory
  • identify the operations and the devices involved in it
  • and accordingly generate control signals to determine

when a given action is to take place.

• We can say that a computer with a microprocessor as

its CPU, is known as Microcomputer.

Microprocessor Characteristics

• Instruction Set:
  • The set of instructions that a microprocessor can

understand.

• Bandwidth:
  • The number of bits processed in a single instruction.
• Capability:
  • It depends upon the number of instructions and

capability of each instruction.

Microprocessor Characteristics

• Word Length:
  • It depends upon the width of internal data bus, registers, ALU etc.
  • An 8-bit microprocessor can process 8 bit data at a time.
  • A processor with longer word length is more powerful and can process data at a faster speed as compared to processor with shorter word length.
  • The word length ranges from 4 bits for small microprocessor, to 64 bits for high-end microcomputers.

Microprocessor Characteristics

• Width of Data Bus:
  • This is the size of the data bus. It defines the number of bits that can be transferred through data bus.
• Width of Address Bus:
  • This parameter decides the memory addressing capability of the microprocessor. The maximum size of the memory unit is decided by this parameter.
• Input/Output Addressing Capability:
  • The maximum number of the input/output ports accessed by the microprocessor depends upon the width of the input/output address provided in the input/output instruction.

Features of Microprocessor

• Cost:
  • The most important feature of a microcomputer is its low cost.
  • Because of the widespread use of microprocessors, the volume of production is very high.
  • That is why, microprocessor chips are available at fairly low prices.
• Size:
  • The second important feature of a microprocessor is its small size.
  • As a result of improvement in fabrication technology, VLSI, electronic circuitry has become so dense that a minute silicon chip can contain hundred and thousands of transistors.

Features of Microprocessor

• Power Consumption:
  • Another important feature is its low power consumption.
  • Microprocessors are normally manufactured by Metal-Oxide semiconductor technology, which has the feature of low power consumption.
• Versatility:
  • The microprocessors are versatile.
  • Keeping the same basic hardware, a microprocessor-based system can be configured for a number of applications by simply altering the software program.
• Reliability:
  • Another important property of microprocessors is its extreme reliability.
  • It has been established that the failure rate of an IC is fairly uniform at the package level, regardless of its complexity.

SYSTEM BUS

System Bus

 The CPU sends various data values,

instructions and information to all the devices

and components inside the computer.

 If you look at the bottom of a motherboard

you'll see a whole network of lines or

electronic pathways that join the different

components together.

 This network of wires or electronic pathways is

called the ' Bus '.

Navjot Rathour