Friday, February 19, 2016

Digital Logic

Overview of Digital Logic

Digital Logic

Binary Logic:
  • Computer uses binary number system because the two voltage levels can be represented as the two digits 0 and 1.
  • Signals in digital electronics have two distinct voltage levels.
  • A system may define 0V as logic 0 and +5V as logic 1.
Logic Gates:
AND Logic:

  • And logic function will output a 1, if all or two of its input are 1.

  • InputsOutput
    XYX AND Y
    000
    010
    100
    111

OR Logic:
  • OR logic function will output a 1, if one or more inputs are 1.

  • InputsOutput
    XYX OR Y
    000
    011
    101
    111

XOR Logic:
  • Performs an exclusive OR operations on the input.
  • Produces 1 output if only one input is 1.
  • A way to remember XOR is "one or the other but not both".
  • Can be used to compare two bits to see if they are the same.

  • InputsOutput
    XYX XOR Y
    000
    011
    101
    110

Buffer:
  • A buffer does not change the logic level of the input.
  • Used to isolate or amplify the signal.

  • InputsOutput
    00
    11

NOT Logic:
  • NOT logic, also called Inverter, outputs the value opposite to that input to the gate.

  • InputsOutput
    XNOT X
    01
    10

NAND Logic:
  • AND logic with an inverter on the output.

  • InputsOutput
    XYX NAND Y
    001
    011
    101
    110

NOR Logic:
  • OR logic with an inverter on the output.

  • InputsOutput
    XYX NOR Y
    001
    010
    100
    110

XNOR Logic:
  • XOR logic with an inverter on the output.

  • InputsOutput
    XYX XNOR Y
    001
    010
    100
    111



Related topics:
Microcomputer System   |   Microcomputer System Architecture   |   Numbering System   |   Memory Basics   |   ASCII Code   |   Computer Internals   |   ROM and RAM Memory

List of topics: Microcomputer

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