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Microprocessor & Interfacing Techniques. Introduction. HISTORY OF MICROPROCESSORS. Computers are accessible to ever-increasing sectors of the world's population.

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History of microprocessors

  • Computers are accessible to ever-increasing sectors of the world's population.

  • Computing hardware has become a platform for uses other than computation, such as automation, communication, control, entertainment, and education.

Microprocessor interfacing techniques1
Microprocessor & Interfacing Techniques

Types of Computers

  • Mainframes

  • Minicomputers

  • Microcomputers

Microprocessor interfacing techniques2
Microprocessor & Interfacing Techniques


  • The largest and most powerful computers are called Mainframes.

  • They are designed to work at a very high speeds with large data words, typically 64 bits or greater.

  • Examples are IBM 4381, Honeywell DPS8, Cray Y-MP/832

Microprocessor interfacing techniques3
Microprocessor & Interfacing Techniques


  • Scaled down version of mainframe computers are often called minicomputers.

  • A minicomputer runs slowly, works directly with smaller data words.

  • Computers of this type are used for business data processing, industrial control and scientific research.

  • Examples are DEC VAX-6360, Data General MV/8000II

Microprocessor interfacing techniques4
Microprocessor & Interfacing Techniques


  • They are the small computers.

  • There are wide range of microcomputers depending on their specification.

  • Some microcomputers have all or most of the features of earlier minicomputers.

  • Microcomputer consist of a CPU ( usually a single integrated circuit) called a microprocessor.

  • Examples are Intel 80-51 single-chip controller, SDK-86, IBM PC, Apple Macintosh.

Microprocessor interfacing techniques5
Microprocessor & Interfacing Techniques

What is a Micro-processor?

  • A Microprocessor is used as a CPU in a microcomputer.

  • A semiconductor chip or chip set that forms the CPU

  • Controls computers input/output devices

  • Executes programs

Microprocessor interfacing techniques6
Microprocessor & Interfacing Techniques

Microprocessor unit (MPU)

  • Consists of an arithmetic logic unit (ALU), a control unit, an instruction decoder and some registers.

  • The MPU Works by sequentially decoding instructions and operating on data under control of a program.

  • The instructions and the data are stored in memory.

Microprocessor interfacing techniques7
Microprocessor & Interfacing Techniques

  • The “Microprocessor” term was used by Intel to name their first CPU (4004). A 4-bit chip designed to be used in a calculator.

  • Architectures now have advanced to 8, 16, 32, 64-bit for general purpose CPUs, and 128/256-bit and higher for specialised microprocessors such as GPUs, DSPs.

  • Term now used to describe the core component of a computer, the “brains” of the system that controls all the rest of the components, the peripherals.

History of microprocessors2

  • The dateis the year that the processor was first introduced. Many processors are re-introduced at higher clock speeds for many years after the original release date.

  • Transistors is the number of transistors on the chip. You can see that the number of transistors on a single chip has risen steadily over the years.

  • Micronsis the width, in microns, of the smallest wire on the chip. For comparison, a human hair is 100 microns thick. As the feature size on the chip goes down, the number of transistors rises.

History of microprocessors3

  • Clock speedis the maximum rate that the chip can be clocked at. Clock speed will make more sense in the next section.

  • Data Widthis the width of the ALU. An 8-bit ALU can add/subtract/multiply/etc. two 8-bit numbers, while a 32-bit ALU can manipulate 32-bit numbers. An 8-bit ALU would have to execute four instructions to add two 32-bit numbers, while a 32-bit ALU can do it in one instruction. In many cases, the external data bus is the same width as the ALU, but not always. The 8088 had a 16-bit ALU and an 8-bit bus, while the modern Pentiums fetch data 64 bits at a time for their 32-bit ALUs.

History of microprocessors4

  • MIPS stands for "millions of instructions per second" and is a rough measure of the performance of a CPU. Modern CPUs can do so many different things that MIPS ratings lose a lot of their meaning, but you can get a general sense of the relative power of the CPUs from this column.

Microprocessor v microcomputer
Microprocessor v Microcomputer

  • A Microprocessor

    • only is a single-chip CPU

    • bus is available

    • RAM capacity, num of port is selectable

    • Communicate by port

  • A Microcomputer

    • contains a CPU and RAM,ROM ,Peripherals, I/O port in a single IC

    • internal hardware is fixed

    • Communicate by port

    • ROM is larger than RAM (usually)

    • Small power consumption

    • Single chip, small board

    • Implementation is easy

    • Low cost

Microprocessor v microcomputers
Microprocessor V Microcomputers

  • Applications

    • Microcomputers are suitable to control I/O devices in designs requiring a minimum component

    • Microprocessors are suitable for processing information in computer systems.

Microprocessor v microcomputers1
Microprocessor V Microcomputers

  • Microcomputer is easy to use and design.

    • Only single chip can be a complete system

    • interfacing to other devices, for example, motors, displays, sensors, and communicate with PC.

  • In contrast, similar system that builds from Microprocessor would require a lot of additional units,

    • such as RAM, UART, I/O , TIMER and etc.

Microprocessor v microcomputers2
Microprocessor V Microcomputers

  • Logic circuit provides limited function for one single design. In order to change circuit’s functionality, we need to redesign the circuits.

  • Microcomputers can reprogram and change functionality of every port, input to output or digital to analog on the fly.

The microcomputers
The Microcomputers

  • All Microcomputers consist of (at least) :

    • Microprocessor Unit (MPU)

    • Program Memory (ROM)

    • Data Memory (RAM)

    • Input / Output ports

    • Bus System

    • (and Software)

  • MPU is the brain of microcomputer


  • Many microcomputers are existing right now.

    • 8051, 68HC11, MSP430, ARM series, and etc.

  • We may widely divide it with how it is designed

    • RISC/CISC architecture.

  • What is the main difference between


  • Does it make any difference to our application?

The microprocessor mpu
The Microprocessor (MPU)

  • The microprocessor is the ‘brain of the microcomputer’

  • Is a single chip which is capable of

    • processing data

    • controlling all of the components which make up the microcomputer system

  • µP used to sequence executions of instructions that is in memory

  • µP Fetch , Decode , and Execute the instruction

  • The internal architecture of the microprocessor is complex.

The microprocessor mpu1
The Microprocessor (MPU)

  • Microprocessor (MPU) typically contains

    • Registers: Temporary storage locations for program instruction or data.

    • The Arithmetic Logic unit (ALU): This part of the MPU performs both arithmetic and logical operations

    • Timing and Control Circuits: that keep all of the other parts of system (Regs, ALU, memory & I/O) working together in the right time sequence


  • Using its ALU (Arithmetic/Logic Unit), a microprocessor can perform mathematicaloperations like addition, subtraction, multiplication and division. Modern microprocessors contain complete floating point processors that can perform extremely sophisticated operations on large floating point numbers.

  • 2. A microprocessor can move datafrom one memory location to another.

  • 3. A microprocessor can make decisionsand jump to a new set of instructions based on those decisions.

The input output i o system
The Input/Output (I/O) System

  • I/O is the link between the MPU and the outside world.

  • An input port is a circuit through which an external device can send signals (data?) to the MPU.

  • An output port is a circuit that allows the MPU to send signals (data?) to external devices.

  • I/O ports connect both digital and analogue devices by DAC and ADC

Introduction 3338016

  • A Bus is a common communications pathway used to carry information between the various elements of a computer system

  • The term BUS refers to a group of wires or conduction tracks on a printed circuit board (PCB) though which binary information is transferred from one part of the microcomputer to another

  • The individual subsystems of the digital computer are connected through an interconnecting BUS system.

Types of buses
Types of Buses

  • There are three main bus groups


    • DATA BUS


Data bus
Data Bus

  • The Data Bus carries the data which is transferred throughout the system. ( bi-directional)

  • Examples of data transfers

    • Program instructions being read from memory into MPU.

    • Data being sent from MPU to I/O port

    • Data being read from I/O port going to MPU

    • Results from MPU sent to Memory

  • These are called read and write operations

Address bus
Address Bus

  • An address is a binary number that identifies a specific memory storage location or I/O port involved in a data transfer

  • The Address Bus is used to transmit the address of the location to the memory or the I/O port.

  • The Address Bus is unidirectional (one way): addresses are always issued by the MPU.

Control bus
Control Bus

  • The Control Bus: is another group of signals whose functions are to provide synchronization ( timing control ) between the MPU and the other system components.

  • Control signals are unidirectional, and are mainly outputs from the MPU.

  • Example Control signals

    • RD: read signal asserted to read data into MPU

    • WR: write signal asserted to write data from MPU

Main memory
Main Memory

  • The duties of the memory are :

    • To store programs

    • To provide data to the MPU on request

    • To accept result from the MPU for storage

  • Main memory Types

    • ROM : read only memory. Contains program (Firmware). does not lose its contents when power is removed (Non-volatile)

    • RAM: random access memory (read/write memory) used as variable data, loses contents when power is removed volatile. When power up will contain random data values

Read only memory
Read only Memory

  • Microprocessor can read instructions from ROM quickly

  • Cannot write new data to the ROM

  • ROM remembers the data, even after power cycled

  • Typically, when the power is turned on, the microprocessor will start fetching instructions from the still-remembered program in ROM (bootstrap )

Types of roms
Types of ROMS

  • Masked ROM or just ROM

  • PROM or programmable ROM(once only)

  • EPROM (erasable via ultraviolet light)

  • Flash (can be erased and re-written about 10000 times, usually must write a whole block not just 1 byte or 2 bytes, slow writing, fast reading)

  • EEPROM (electrically erasable read-only memory, also known as EEROM—both reading and writing are very slow but can program millions of times…useless for storing a program but good for say configuration information.

Introduction 3338016

  • On a PC, the ROM is called the BIOS (Basic Input/Output System). When the microprocessor starts, it begins executing instructions it finds in the BIOS. The BIOS instructions do things like test the hardware in the machine, and then it goes to the hard disk to fetch the boot sector. This boot sector is another small program, and the BIOS stores it in RAM after reading it off the disk. The microprocessor then begins executing the boot sector's instructions from RAM. The boot sector program will tell the microprocessor to fetch something else from the hard disk into RAM, which the microprocessor then executes, and so on. This is how the microprocessor loads and executes the entire operating system.


  • You should be able to define terms microcomputer, microprocessor, computer types, memory, bus, input/output devices.