CSCI-235 Micro-Computers in Science - PowerPoint PPT Presentation


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CSCI-235 Micro-Computers in Science


CSCI-235 Micro-Computers in Science Hardware Design Part I – PowerPoint PPT presentation

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Title: CSCI-235 Micro-Computers in Science

CSCI-235Micro-Computers in Science
  • Hardware Design
  • Part I

  • Electricity and Switches
  • Modern computers are powered by electricity,
    using electrical signals to store and manipulate
  • The components of a computer require electrical
    power to carry out their assigned task
  • Electricity generates the light that shines
    through a computer screen, illuminating the
    individual pixels that make up images and letters
  • Electricity runs the motor that spins the
    hard-drive disk, allowing information to be
  • Main memory and CPU employ electrical signals to
    store and manipulate data
  • Bit patterns are represented by the presence or
    absence of electrical current along a wire

  • Switches
  • The most basic tool for controlling the flow of
    electricity is a switch
  • A switch can be flipped to connect or disconnect
    two wires, thus regulating the flow of
    electricity between them

  • Transistors
  • A transistor is a solid piece of metal attached
    to a wire that serves as a switch by
    alternatively conducting or resisting electricity
  • Solid-state switches either permit or block
    current flow
  • A control input causes state change

  • A large number of transistors, as well as the
    electrical conducting paths that connect them,
    can be printed photographically on a wafer of
    silicon to produce a device known as an
    integrated circuit or, more commonly, a chip
  • At current technology levels, 25 million or more
    transistors can fit into a space only 1cm2
  • Transistors can be combined to form a circuit,
    which controls the flow of electricity in order
    to produce a particular behavior

  • The production of integrated circuits is one of
    the most complex engineering processes in the
  • Transistors on chips can be as small as .065
    microns (roughly 1/1,500th the width of human
  • Since a hair or dust particle can damage
    circuitry during manufacture, chips are created
    in climate-controlled "clean rooms"

  • Gate
  • The term gate suggests a simple circuit that
    controls the flow of electricity
  • In the case of a NOT gate, the flow of
    electricity is manipulated so that the output
    signal is always opposite of the input signal
  • We can think of a gate as computing a function of
    binary values
  • 0 represents no current 1 represents current
  • symbol to the left (triangle w/ circle) used to
    denote NOT gate
  • truth table to right describes mapping of input
    to output

  • Many other simple circuits can be defined to
    perform useful tasks
  • AND gate produces voltage on its output wire if
    both input wires carry voltage
  • OR gate produces voltage on its output wire if
    either input wire carries voltage
  • AND, OR, and NOT gates can be combined to
    construct all the circuitry required to store and
    manipulate information within a computer

  • Boolean Logic and Gates
  • Boolean logic describes operations on true/false
  • True/false maps easily onto bistable environment
  • Boolean logic operations on electronic signals
    can be built out of transistors
  • Boolean operations
  • a AND b
  • True only when a is true and b is true
  • a OR b
  • True when a is true, b is true, or both are true
  • NOT a
  • True when a is false and vice versa

  • Boolean expressions
  • Constructed by combining together Boolean
  • Example (a AND b) OR ((NOT b) AND (NOT a))
  • Truth tables capture the output/value of a
    Boolean expression
  • A column for each input plus the output
  • A row for each combination of input values
  • Example (a AND b) OR ((NOT b) and (NOT a))

  • Gates

  • Abstraction in hardware design
  • Map hardware devices to Boolean logic
  • Design more complex devices in terms of logic,
    not electronics
  • Conversion from logic to hardware design can be

  • Circuits
  • A circuit is a collection of logic gates
  • Transforms a set of binary inputs into a set of
    binary outputs
  • Values of the outputs depend only on the current
    values of the inputs