Developed in the 1970's, Fire Codes are basically a tricky way of providing the same results as row and column parity or CRC. They are very fast to decode and check, and can be used to correct errors as well.
Fire codes operate because of the careful selection of the CRC-generating polynomial. (X^ 23 +1)( X^ 17 +X^3 +1) These special polynomials contain two prime-polynomial factors, each of which helps locate a detected error. Knowing the location of a transmitted error modulo and the degree of each of these prime-polynomial factors, you can apply the Chinese remainder theorem to locate the exact bit error. Although the math sounds complex, you can easily implement it with high-speed D flip-flops and XOR gates. If a 32-bit fire-code-protected block contains two errors separated by exactly 11 bits, the fire code fails to correct the errors.
Google: fire code error correction
Data * - - - - - - - * * - - * - - - - * - - * bits - * - - - - - - * - * - - * - - - * - - * - - * - - - - - * - - * - - * - - * - - * - - - * - - - - * - - - * - - * - * - - * - - - - * - - - * - - - - * - - * * - - * - - - - - * - - * - - - - - * - - X - - * - - - - - - * - * - - - - - - * - * * - * - - - - - - - * * - - - - - - - * * - * * Parity = = = = = = = = P = = = = = = = = ! = = !
Each parity bit is the XOR of parity for the data byte with which it is
associated and parity for staggered bits from the eight previous bytes.
Essentially, it is a clever way to obtain the same results as are provided
by the use of row and column parity bits. (After the last byte of data, one
extra byte, with the extra parity bit, is needed to provide parity for all
the remaining diagonals.)
|file: /Techref/method/error/firecodes.htm, 3KB, , updated: 2009/1/23 11:33, local time: 2017/11/18 23:00,
|©2017 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions?|
<A HREF="http://www.piclist.com/techref/method/error/firecodes.htm"> Fire codes</A>
|Did you find what you needed?|
PICList 2017 contributors:
o List host: MIT, Site host massmind.org, Top posters @20171118 RussellMc, Van Horn, David, James Cameron, Sean Breheny, alan.b.pearce, IVP, Neil, David C Brown, Bob Blick, Denny Esterline,
* Page Editors: James Newton, David Cary, and YOU!
* Roman Black of Black Robotics donates from sales of Linistep stepper controller kits.
* Ashley Roll of Digital Nemesis donates from sales of RCL-1 RS232 to TTL converters.
* Monthly Subscribers: Gregg Rew. on-going support is MOST appreciated!
* Contributors: Richard Seriani, Sr.
Welcome to www.piclist.com!