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Parity Bit
What is it?
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A parity bit, check bit, is an added to a string of binary code that indicates whether the number of 1-bits in the string is even or odd.
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Parity bits are used as the simplest form of error detecting code.
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It only detects single bit error not more than a single bit.
0 1 0 1 1 1 0 0
0
Original Binary Data
(8 - bit)
Parity Bit
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An extra bit added.
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It is a concept to detect errors.
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A single bit error is detected by it.
Types of Parity Bit
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There are two variants of parity bits :
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even parity bit
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odd parity bit
Parity Bit
Even Parity Bit
Odd Parity Bit
Even Parity Bit :
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For a given set of bits, count the occurrences of 1's value.
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If that count is odd, the parity bit value is set to 1.
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If that count is already even, the parity bit value is set to 0.
011
Original Signal
Transmitter
0110
Receiver
0110
Output Signal
Parity bit added to the original signal.
Make the total no. of 1 in transmitting signal even.
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Even parity is a special case of a cyclic redundancy check.
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Even parity Generator :
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Error detection will check at the receiver end. For even parity, the receiver needs to count even no. of 1.
Odd Parity Bit :
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For a given set of bits, count the occurrences of 1's value.
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If that count is even, the parity bit value is set to 1.
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If that count is alredy odd, the parity bit value is set to 0.
011
Original Signal
Tranmitter
Receiver
0111
0111
Output Signal
Parity bit added to the original signal.
Make the total no. of 1 in transmitting signal odd.
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Even parity Generator :
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For odd parity, the receiver needs to count odd no. of 1 for error detection.
3-bit even-odd parity table :
Use
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The parity bit is generally applied to the smallest units of communication protocol.
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Also, the can also be applied separately to an entire message string of bits.
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This means parity checks are not 100% reliable when validating data.
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Most reliable when using small packet sizes.
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