A parity generator computes the extra check bit before transmission. A checker combines the received data and parity bit to decide whether the chosen parity rule holds. XOR gates naturally implement even-parity generation and checking because they report whether the number of ones is odd.
Worked example
For data 1001, the even-parity generator computes 1 XOR 0 XOR 0 XOR 1 = 0. Send parity zero. At the receiver, XOR all five bits: a zero result passes the even-parity check. If one data bit flips, the check result becomes one.
What to watch for
A passing check does not prove that every bit is correct: an even number of flips can escape detection. State the error model when choosing a code.
Try it yourself
What even-parity bit should accompany 1110?
Answer: The data has three ones, so parity must be one. The complete group then has four ones.
How to study this topic
Name each input and define its active level before drawing gates. Follow one data path at a time, then check the other combinations. A complete specification is the best starting point for a reliable circuit.
Explore related programmes
These recorded programmes are upcoming. This article is general educational content, not a syllabus or course sample.
Digital Electronics