@ YU4CFG, I just finished my HSC, so this should be still fresh in my head.<br /><br />The checksum created (when checksum error checking is used) when a block of data is transmitted can itself be used to generate a more useful error detection value. CRC works as follows...<br />1. The checksum number is substituted into a formula and a sixteen bit remainder is calculated<br />2. Once the data has reached its destination, the received checksum is put through the same process<br />3. If the remainder prduced is identical to the received then data has been correctly received, otherwise a retransmission is requested<br /><br />This is the best error checking method, depending on the application, well... out of all the other ones we were taught.<br /> <br /> <small>[ 26. November 2004, 08:16 PM: Message edited by: reuder ]</small>