* Question
What is the output function of the parity error signal?
* Answer
The output function of the parity error signal is used in digital systems to detect errors in data transmission or storage, specifically errors related to parity bits. Parity is a form of error detection where an extra bit (the parity bit) is added to a data word to ensure that the total number of 1’s in the word is either even or odd.
Parity Error Signal Output Function:
The parity error signal indicates whether the received or processed data has a parity error — meaning whether the number of 1’s in the data word does not match the expected parity.
Even Parity: The parity bit is set so that the total number of 1’s in the data, including the parity bit, is even.
If the total number of 1’s is odd, a parity error is detected, and the parity error signal will activate (typically high).
If the total number of 1’s is even, no parity error is detected, and the error signal remains inactive (typically low).
Odd Parity: The parity bit is set so that the total number of 1’s, including the parity bit, is odd.
If the total number of 1’s is even, a parity error is detected, and the parity error signal will activate (typically high).
If the total number of 1’s is odd, no parity error is detected, and the error signal remains inactive (typically low).
Example:
For an even parity system, suppose the data word is 1010110 (which has 4 ones). The parity bit would be set to 0 to keep the total number of ones even. If the received data word is 1010111 (which has 5 ones, odd), the parity error signal will be triggered (indicating an error).
For an odd parity system, suppose the data word is 1010110 (which has 4 ones). The parity bit would be set to 1 to make the total number of ones odd. If the received data word is 1010110 (still has 4 ones, even), a parity error signal would be triggered.
Output Function in Digital Circuits:
Parity Error Signal = 0 (No error): This means that the parity check has passed (the received data has the correct parity).
Parity Error Signal = 1 (Error detected): This means that the parity check has failed (the number of 1’s doesn’t match the expected parity).
This function is crucial for ensuring the integrity of data in systems like memory devices, communication systems, or any digital system where reliable data transmission is needed.
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