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Question

Which of the following gates can be used for parity generation?

The correct answer is

XOR gate

In digital electronics and data communication, parity generation is a crucial process used for error detection. It involves adding an extra bit, called a parity bit, to a binary word to ensure that the total number of '1's in the word (including the parity bit) is either even (for even parity) or odd (for odd parity).

The question asks which of the given logic gates can be used for parity generation. Let's analyze the characteristics of each gate in relation to this function.

XOR Gate for Parity Generation

The XOR gate, or Exclusive-OR gate, is fundamental to parity generation. Its unique characteristic is that it outputs a '1' only when an odd number of its inputs are '1'. If an even number of its inputs are '1', it outputs a '0'. This behavior perfectly aligns with the concept of determining parity. For a 2-input XOR gate (A \(\oplus\) B):

  • If A and B are both '0' (an even number of 1s), the output is '0'.
  • If A is '0' and B is '1' (an odd number of 1s), the output is '1'.
  • If A is '1' and B is '0' (an odd number of 1s), the output is '1'.
  • If A and B are both '1' (an even number of 1s), the output is '0'.

This behavior can be extended to multiple inputs by cascading XOR gates. For example, to find the parity of three bits A, B, and C, you would use \((A \oplus B) \oplus C\). The final output will be '1' if there is an odd number of '1's among A, B, and C, and '0' if there is an even number of '1's.

Therefore, the XOR gate directly performs the function required for parity generation: checking whether the count of '1's is odd or even.

Truth Table for a 2-Input XOR Gate
Input A Input B Output (A \(\oplus\) B)
0 0 0
0 1 1
1 0 1
1 1 0

Other Logic Gates for Parity Generation

Let's briefly consider why the other gates are not suitable for parity generation:

  • AND gate: An AND gate outputs '1' only if all its inputs are '1'. It does not provide information about the odd or even count of '1's for parity.
  • NAND gate: A NAND gate is the inverse of an AND gate. It outputs '0' only if all its inputs are '1'. Like the AND gate, it is not designed to detect the odd or even count of '1's.
  • OR gate: An OR gate outputs '1' if at least one of its inputs is '1'. It tells you if there's any '1' present, but not whether the number of '1's is odd or even, which is essential for parity generation.

Conclusion on Parity Generation

Based on the functionality of various logic gates, the XOR gate is the only one among the given options that inherently provides the required logic for parity generation. Its ability to output a '1' when an odd number of inputs are high makes it perfect for this application in error detection circuits.

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Important Questions from Digital Electronics

  1. Latches are _______ circuits.

  2. First generation computers had which of the following?

  3. The 8085 has two registers known as primary data pointers. These are registers

  4. Which of the following is a non-positional number system?

  5. The digital equivalent of an electric series circuit is the:

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