In any case, the error-correcting logic can't tell the difference between single bit errors and multiple bit errors, and so the corrected output can't be relied on. Hamming codes If more error-correcting bits are included with a message, and if those bits can be arranged such that different incorrect bits produce different error results, then bad bits could Retrieved 2014-08-12. ^ "Documentation/edac.txt". For missions close to Earth the nature of the channel noise is different from that which a spacecraft on an interplanetary mission experiences. have a peek here
This leaves Bit 3; changing its value gives us the correct ECC bits and confirms the correct data. Join them; it only takes a minute: Sign up Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to the As of 2009, the most common error-correction codes use Hamming or Hsiao codes that provide single bit error correction and double bit error detection (SEC-DED). If the new check bits are XOR'd with the received check bits, an interesting thing occurs.
Otherwise, the sum of the positions of the erroneous parity bits identifies the erroneous bit. Google dealt setback in age bias case by judge interested in 'Googleyness' An age discrimination lawsuit against Google has been approved as a '"collective action" by a federal... Parity has a distance of 2, so one bit flip can be detected, but not corrected and any two bit flips will be invisible. However, if this twelve-bit pattern was received as "1010 1011 1011" – where the first block is unlike the other two – it can be determined that an error has occurred.
This type of code is called a SECDED (single-error correcting, double-error detecting) code. Comments By Russell Kay Computerworld | Nov 1, 2004 12:00 AM PT RELATED TOPICS Networking Comments