# Logic and Logic Gates

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Introduction

BTEC NATIONAL CERTIFICATE - it practitioners [general] Centre 31200 Assignment number: 4 Logic and Logic Gates Students Name (a) UNIT title Computer Architecture (b) Unit Number 9 Date of Issue 5 May Date due 19 May 2009 Re-submission date Criteria Achieved Criteria Achieved Criteria Achieved Criteria Achieved P7 criteria achieved Criteria achieved criteria achieved criteria achieved M2 M4 criteria achieved Criteria achieved criteria achieved criteria achieved D1 Task 1 Task 2 Task 3 Task 4 P1 describe using examples how numeric and alphanumeric data can be coded within a computer system M1 explain using examples how data travels around the processor D1 create complex logic circuits made up of arrays of simple logic circuits P2 describe how analogue data can be converted and stored in computer systems M2 create logic circuits using simple logic gates and provide truth tables and explanation as to their operation D2 compare and contrast two different processors. P3 convert numeric data between different number systems including floating point M3 create low-level programs which involve decision making and branching P4 carry out manipulation of numeric data held in three different number systems M4 describe the difference between astable and bistable flip-flops. ...read more.

Middle

[D1] LOGIC GATES Truth Table Input Output LIST OF LOGIC GATES 1. AND 2. OR 3. NOT 4. NAND 5. NOR 6. XOR 7. XNOR WORKING OUT TRUTH TABLES All of the logic gates obviously have a truth table. The formula for working out the number of possible outputs is 2n. N is the number of inputs. E.g. if there are 2 inputs than the formula would be 22. The answer is 4. This means that there are 4 possible outputs. Truth Table Input Output AB Q 00 0 01 0 10 0 11 1 1. AND GATE In AND gates the output can only be 1 if all the inputs are all 1 and if either of the output are 0 and the other input is 1 than output will always be 0. The two inputs AB and output Q represent the expression which in effect is right because the stands for AND. Truth Table Input Output ABC Z 000 1 001 1 010 1 011 1 100 1 101 1 110 1 111 0 2. NAND GATE A NAND gate can have more than 2 inputs. ...read more.

Conclusion

If the input is 1 than output is 0 and if the output is 1 than output has to be 0. The logical expression is which means Q = NOT A. 6. XOR Truth Table Input Output AB Q 00 0 01 1 10 1 11 0 This type of gate is implemented in computers for binary addition. If both the inputs are 0 than the output will also be 0 and if both the inputs are 1 than the output will also be 0. XOR is actually short for exclusive OR. The logical expression for the XOR gate is which means that Q = (A AND NOT B) OR (B AND NOT A). Truth Table Input Output AB Q 00 1 01 0 10 0 11 1 7. XNOR This type of gate is simply the inverse of XOR (exclusive OR). You can only get a result of 1 is both the inputs are same either 00 or 11. If the inputs are different e.g. 0 and 1 or 1 and 0 than the output will be 0. The expression for this type of gate is. ?? ?? ?? ?? North Warwickshire & Hinckley College BTEC_NAT_U9_A3 1 Unit 09: Assignment 4 Anas Patel ...read more.

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