Longitudinal parity check
Longitudinal redundancy check (engl. Longitudinal redundancy check , therefore often LRC ) is a method for detection of 1-bit errors in digital data transmission , by a certain number of transmitted data words a check sum or a parity data word is formed.
Example: checksum
An additional data word is transmitted, whereby the modulo sum of the previously transmitted data words and this test data word must result in a previously defined value (usually zero).
Example: parity data word
It is provided an additional parity data word column-wise parity generated. This means that, depending on the agreement, the respective total over a column must result in an even (same parity) or an odd number (unequal parity). If this is not the case, an error has occurred during the transfer. If two bit errors occur in the same column during transmission , this cannot be determined by this parity check method, since the column sums then again meet the requirements. The following example shows three bytes and the associated parity byte for creating the same parity in columns.
11011001
10111001
00110011
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01010011 → parity data word
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22242024 → Column totals