Diana

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Diana

  1. 1. LOGIC GATES
  2. 2. BINARY LOGIC <ul><li>Binary logic deals with variables that can take on only two possible discrete values and with operations that assume logical meaning. The paired values that a variable may take may be referred to as: true and false or yes and no. For our purpose, it is more convenient to think of these values as 1 and 0. </li></ul><ul><li>1-high and 0- low </li></ul>
  3. 3. DIGITAL LOGIC GATES <ul><li>The eight standard gates used in digital design are: </li></ul><ul><ul><ul><ul><ul><li>INVERTER </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>OR 3 basic logical operations </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>AND </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>BUFFER </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>NAND </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>NOR </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>EXCLUSIVE OR </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>EXCLSIVE NOR </li></ul></ul></ul></ul></ul>
  4. 4. SYMBOLS inverter or and buffer NAND NOR XOR XNOR
  5. 5. INVERTER GATE <ul><li>One of the most basic operations in a digital system is inversion, or negation. </li></ul>V i V o V i V o 0 0 1 1 The output state is always the opposite of the input state
  6. 6. OR GATE <ul><li>An OR GATE has two or more input signals but only one output signal. It is called an OR GATE because the output is high if any or all the input are high. </li></ul>V a V b V o V a V b V o 0 0 1 1 0 1 0 1 0 1 1 1
  7. 7. AND GATE <ul><li>has a high output only when all its inputs are high. </li></ul>V a V b V o V a V b V o 0 0 1 1 0 1 0 1 0 0 0 1 When all inputs are low (0), the output is low. The only way to get a high output (1) is to raise all inputs to a high state.
  8. 8. BUFFER <ul><li>A buffer allows a transfer of function without implementing any particular operation. </li></ul>V i V o V i V o = V i V o V i V o 0 1 0 1 The binary value of the output is equal to the binary value of the input.
  9. 9. NAND GATE <ul><li>- The NAND GATE can have two or more input but has only one output. </li></ul>V a V b V o V a V b V o 0 0 1 1 0 1 0 1 1 1 1 0 V a V b V o All inputs must be high to produce a low output.
  10. 10. NOR GATE <ul><li>The NOR GATE can have two or more inputs but has only one output. </li></ul>V a V b V o V a V b V o 0 0 1 1 0 1 0 1 1 0 0 0 V a V b V a V b V o All inputs must be low to produce a high output.
  11. 11. EXCLUSIVE – OR GATE (XOR) <ul><li>An XOR is a 2- input gate that is similar in output to an OR GATE except that the XOR produces a 0 output when both input are 1. </li></ul>V a V b V o V a V b V o 0 0 1 1 0 1 0 1 0 1 1 0
  12. 12. EXCLUSIVE – NOR GATE (XNOR) <ul><li>The complement of the XOR is the XNOR gate. A 2- input XNOR is gate whose output is 1 whenever its 2 inputs are the same. </li></ul>V a V b V o V a V b V o 0 0 1 1 0 1 0 1 1 0 0 1 V a V b V o An XNOR gate is logically equivalent to an XOR gate followed by an inverter.
  13. 13. XNOR Y = AB + AB BUFFER Y = A BOOLEAN EXPRESSIONS
  14. 14. EXAMPLE
  15. 15. EXAMPLE
  16. 16. <ul><li>끝 </li></ul>

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