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# Ee2 chapter3 basic_logicgates

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### Ee2 chapter3 basic_logicgates

1. 1. IT2001PAEngineering Essentials (2/2)Chapter 3 - Basic Logic Gates Lecturer Namelecturer_email@ite.edu.sg Nov 20, 2012Contact Number
2. 2. Chapter 3 - Basic Logic GatesLesson ObjectivesUpon completion of this topic, you should be able to: Relate the operation of basic logic gates such as AND, OR, NOT, NAND, NOR, EX-OR and EX-NOR, and construct its truth table. IT2001PA Engineering Essentials (2/2) 2
3. 3. Chapter 3 - Basic Logic GatesSpecific Objectives Students should be able to :  Explain the use of logic gate.  Describe the function of the basic logic gates (i.e. NOT, AND, NAND, OR, NOR, EX-OR and EX-NOR) with the help of symbol, truth table and its equivalent switching circuit.  Describe how NOT, AND, OR, NOR can be constructed from NAND gates.  Describe how NOT, AND, OR, NOR can be constructed from NOR gates. IT2001PA Engineering Essentials (2/2)
4. 4. Chapter 3 - Basic Logic GatesLogic Gates In digital logic system, events are described as either ‘0’ or ‘1’ Logic 1 Logic 0 Switch ON Switch OFF Bulb lights up Bulb unlighted High Low True False 5 volts 0 volts 2.4V to 5V 0V to 0.4V IT2001PA Engineering Essentials (2/2) 4
5. 5. Chapter 3 - Basic Logic GatesLogic Gates Positive Logic In a positive logic system, a high voltage is used to represent logical true(1), and a low voltage for logical false (0). In positive logic circuits it is normal to use +5V for true and 0V for false. Negative Logic In a negative logic system, a low voltage is used to represent logical true (1) and a high voltage for a logical false (0). IT2001PA Engineering Essentials (2/2) 5
6. 6. Chapter 3 - Basic Logic GatesGate - it has 2 or more binary inputs and 1 output Binary Binary Inputs Gate Output IT2001PA Engineering Essentials (2/2) 6
7. 7. Chapter 3 - Basic Logic Gates7 Basic Logic Gates AND gate OR gate INVERTER ( NOT ) gate NAND gate NOR gate XOR gate XNOR gate IT2001PA Engineering Essentials (2/2) 7
8. 8. Chapter 3 - Basic Logic GatesTruth Table Table which relates the output of a logic function to all the possible combinations of the inputs. The number of possible combinations of the inputs is equal to 2N, where N is the number of inputs A logic gate with 2 inputs 22= 4 possible combinations from its inputs Inputs Output 0 0 Depends on the logic function 0 1 Depends on the logic function 1 0 Depends on the logic function 1 1 Depends on the logic function IT2001PA Engineering Essentials (2/2) 8
9. 9. Chapter 3 - Basic Logic GatesThe AND Operation A B L=A.B Lamp: Off=0 Switch: Open=0 ON=1 Closed=1 IT2001PA Engineering Essentials (2/2) 9
10. 10. Chapter 3 - Basic Logic GatesTruth Table of AND Gate A B L Lamp : Off = 0 0 0 0 On = 1 0 1 0 1 0 0 Switch : Open =0 Closed=1 1 1 1 IT2001PA Engineering Essentials (2/2) 10
11. 11. Chapter 3 - Basic Logic GatesThe AND Gate Symbol A B Y=A.B.C C Equation : Y = A.B.C IT2001PA Engineering Essentials (2/2) 11
12. 12. Chapter 3 - Basic Logic GatesSummary of AND Gate The AND gate produces a HIGH output only when all of the inputs are HIGH 1 1 1 When any of the inputs is LOW, the output is LOW 0 1 0 0 0 0 1 0 0 IT2001PA Engineering Essentials (2/2) 12
13. 13. Chapter 3 - Basic Logic GatesTruth Table of AND Gate A B C L 0 0 0 0 0 0 1 0 0 1 0 0 0 1 1 0 1 0 0 0 1 0 1 0 1 1 0 0 1 1 1 1 Output = 1 only 1 1 1 1 if all inputs are 1 IT2001PA Engineering Essentials (2/2) 13
14. 14. Chapter 3 - Basic Logic GatesExample Determine the output waveform for the AND gate shown. A 0 1 0 0 1 0 A Y B 0 0 0 1 0 B 1 Y 0 0 0 0 0 1 IT2001PA Engineering Essentials (2/2) 14
15. 15. Chapter 3 - Basic Logic GatesThe OR Operation A B Lamp: OFF= 0 Switch: Open=0 ON=1 Closed=1 IT2001PA Engineering Essentials (2/2) 15
16. 16. Chapter 3 - Basic Logic GatesTruth Table of OR Gate A B L Lamp : OFF =0 0 0 0 ON=1 0 1 1 1 0 1 Switch : Open=0 Closed=1 1 1 1 IT2001PA Engineering Essentials (2/2) 16
17. 17. Chapter 3 - Basic Logic GatesThe OR Gate Symbol A B Y C Equation : Y = A + B + C IT2001PA Engineering Essentials (2/2) 17
18. 18. Chapter 3 - Basic Logic GatesSummary of OR Gate The output is LOW only when all the inputs are LOW 0 0 0 The OR gate produces a HIGH on the output when any of the inputs is HIGH 1 0 1 1 1 1 0 1 1 IT2001PA Engineering Essentials (2/2) 18
19. 19. Chapter 3 - Basic Logic GatesTruth Table of OR Gate A B C L 0 0 0 0 0 0 1 1 0 1 0 1 0 1 1 1 1 0 0 1 1 0 1 1 1 1 0 1 Output = 1 only if 1 1 1 1 any of inputs is 1 IT2001PA Engineering Essentials (2/2) 19
20. 20. Chapter 3 - Basic Logic GatesExample Draw the output waveform for the OR gate A A0 1 0 1 0 Y B B 0 1 1 0 0 Y 0 1 1 1 0 IT2001PA Engineering Essentials (2/2) 20
21. 21. Chapter 3 - Basic Logic GatesThe NOT Operation (Inverter) Symbol A A A A Equation Y = A IT2001PA Engineering Essentials (2/2) 21
22. 22. Chapter 3 - Basic Logic GatesTruth Table of Inverter Inputs Output 0 1 1 0 Its logic output is always the inverse of the logic inputs IT2001PA Engineering Essentials (2/2) 22
23. 23. Chapter 3 - Basic Logic GatesNAND Gate A A X=AB X=AB B B Equation X= AB X= AB IT2001PA Engineering Essentials (2/2) 23
24. 24. Chapter 3 - Basic Logic GatesTruth Table of NAND Gate Inputs AND NAND A B AB AB 0 0 0 1 0 1 0 1 1 0 0 1 1 1 1 0 IT2001PA Engineering Essentials (2/2) 24
25. 25. Chapter 3 - Basic Logic GatesSummary of NAND Gate The NAND gate produces a LOW output only when all the inputs are HIGH 1 0 1 When any of the inputs is LOW , the output will be HIGH 0 1 0 1 1 1 1 0 0 IT2001PA Engineering Essentials (2/2) 25
26. 26. Chapter 3 - Basic Logic GatesExample Draw the output waveform for the NAND gate shown 0 0 A 0 1 1 A Y B 0 0 1 1 1 B Y 1 1 IT2001PA Engineering Essentials (2/2) 26
27. 27. Chapter 3 - Basic Logic GatesNOR Gate A A X=A+B X=A+B B B Equation X= A+B X= A+B IT2001PA Engineering Essentials (2/2) 27
28. 28. Chapter 3 - Basic Logic GatesTruth Table of NOR Gate Inputs OR NOR A B A+B A+B 0 0 0 1 0 1 1 0 1 0 1 0 1 1 1 0 IT2001PA Engineering Essentials (2/2) 28
29. 29. Chapter 3 - Basic Logic GatesSummary of NOR Gate The NOR gate produces a HIGH output only when all the inputs are LOW 0 1 0 When any of the inputs is HIGH , the output will be LOW 0 1 1 0 0 0 1 0 1 IT2001PA Engineering Essentials (2/2) 29
30. 30. Chapter 3 - Basic Logic GatesExample Draw the output waveform for the NOR gate shown A 0 1 0 1 0 1 A Y B 1 1 0 1 0 0 B Y 0 0 1 0 0 1 IT2001PA Engineering Essentials (2/2) 30
31. 31. Chapter 3 - Basic Logic Gates EX-OR Gate EX-NOR Gate IT2001PA Engineering Essentials (2/2) 31
32. 32. Chapter 3 - Basic Logic GatesEX-OR Gate Truth Table A B Y A 0 0 0 X = A ⊕B B 0 1 1 1 0 1 1 1 0 Logic Equation X = AB + A B Its output is High only when the X = A⊕B inputs are at different levels. IT2001PA Engineering Essentials (2/2) 32
33. 33. Chapter 3 - Basic Logic GatesEX-NOR Gate Truth Table A A B Y X = A⊕B 0 0 1 B 0 1 0 1 0 0 1 1 1 Logic Equation X = A B + AB Its output is High only when the inputs are X = A⊕B at the same levels. IT2001PA Engineering Essentials (2/2) 33
34. 34. Chapter 3 - Basic Logic GatesExercise on Timing DiagramDraw the output waveform X of the EX-OR gate with inputsA and B given below: A X B A B X IT2001PA Engineering Essentials (2/2) 34
35. 35. Chapter 3 - Basic Logic GatesExercise on Timing Diagram Draw the output waveform X of the EX-NOR gate with inputs A and B given below: A X B A B X IT2001PA Engineering Essentials (2/2) 35
36. 36. Chapter 3 - Basic Logic GatesNext Lesson IT2001PA Engineering Essentials (2/2) 36