Microprocessor is a
Register-based electronic device
Reads binary instruction from a storage device
Accepts binary as input
Processes data according to instruction
Provides Result as output
A Programmable Device
• MP Applications are classified into two Categories:
• Reprogrammable system
MP is used for computing and data Processing
It includes General Purpose MP, Mass storage device and
• Embedded System
The MP is a part of final product
Reprogramming is not possible
• MP operates in binary digits 0 & 1,also know as a bits.
• Bits are represented in terms of Electrical Voltages in Machine
0 Represents one voltage level and 1 represents another
also known as Low and High respectively.
• Each MP recognizes and processes a group of bits called word
• MP are classified according to their word Length.
• Memory is like the pages of a notebook
space for storing a fixed binary numbers on each line
• These pages are generally made of semiconductor material.
• Each line is an 8-bit register that can store eight binary bits.
• several 8-bit registers are arranged in a sequence called
• Input Device
The user can enter instruction and data into memory
through Input devices.
Ex : key board or simple switches.
• Output Device
Result can be displayed by a output devices.
Ex: seven segment LEDs(Light Emitting Diodes) or printed
by a Printer.
Block Diagram of a Computer
Advance in Semiconductor Technology
Since 1950 Entire circuit consisting of several transistors, diodes and registers
could be designed on a single chip(Integrated Circuit).
In early 1960 technology of integrating of circuits of a logic gates on a single
chip became known as small scale integration(SSI).
More than 100 gates were fabricate on single chip which was called medium
More than 1000 gates on a single chip which was called Large scale
Now we are in era of Very Large Scale Integration(VLSI) and Super Large Scale
• In 1969, Intel received a contract from Japanese
company, Busicom, to design a programmable calculator.
• Ted Hoff suggested a general purpose chip that could perform
various logic functions.
• Intel coined term “Microprocessor” and in 1971 released first 4-bit
microprocessor as the 4004.
• Gordon Moore, cofounder of Intel Corporation, predicted that
number of transistors per IC would double every 18 months, this
came to known as “Moore’s Law”
• The Intel 4004 was quickly replaced by 8-bit microprocessor(Intel 8008)
which was in turn superseded by Intel 8080.
• Intel 8080 widely used in control application and small computers also
were designed using 8080 as CPU, these computers became known as
• Within few years Motorola 6800,the Zilog Z80 & Intel 8085 Microprocessor
were developed as improvements over 8080.
• The 8085 and Z80 were designed as upward software compatible with
• 8085 developed in 1976, which has 16bit address bus and 8bit data bus.
Organization of a MicroprocessorBased System
MP can be divided into three segments
• Arithmetic Logic Unit :
Performs Arithmetic & Logic Operation
• Register Array :
Primarily used to store data during execution of program
• Control Unit :
Provides Necessary timing and control signals to all
• Memory stores binary information which may be
Instruction or data.
• Microprocessor fetch that information from memory.
• ROM (Read Only Memory)
Used to store Programs that do not need alterations
• R/WM(Read/Write Memory) / RAM
R/WM also know an User Memory, used to store user
programs and data.
• Communication Path
• It is nothing but a group of wires to carry bits.
• All peripheral share the same bus however the MP
communicate with only one peripheral at a time.
• The timing is provided by control unit of MP.
Microprocessor Instruction Set and Computer
Byte = 8 bits
Nibble = 4 bits
High Level Language
Compiler or Interpreter
8085 Machine Language
• Machine language- a binary language composed of 0 and 1.
• Designer decide the combination of 0 and 1 for specific
function this is called instruction.
• Ex: 0001 1100 Increment accumulator.
• Ex: 1000 0000 Adding accumulator and register B data.
• 74 instruction for performing various operation.
8085 Assembly Language
• Need of 8085 Assembly Language
• Symbolic code of each instruction is called mnemonic
• Ex: INR A similarly the binary code 1000 0000
• ADD B Adding content of accumulator with register B
• Program written in mnemonic is called as assembly language
• Assembler convert ASCII code to binary code.
• Machine Independent are called High level language
• Ex: Basic, Pascal, C, C++, and Java.
• Program accept English like statement as input is called source
• The compiler or interpreter translate the source code into