| 摘要 |
The present invention relates to apparatus for generating a set of CRC check bytes for a variable-length record formed as a sequence of data bytes and error correction check bytes inserted into the sequence of data bytes at preselected intervals. The apparatus comprises a computing system adapted to operate on the sequence of data bytes and error correction check bytes in order to generate the set of CRC check bytes.
<??>According to the invention the apparatus is characterised in that the computing system comprises
first computing means for sequentially receiving the sequence of data bytes and error correction check bytes in the record and for multiplying all the data bytes and error correction check bytes, except for a first preselected set of the error correction check bytes, by a matrix of the form T<-n>, where n is an integer and different from any integer used for computing the error correction check bytes, in order to generate a first sub-set of CRC check bytes,
second computing means for sequentially receiving the sequence of data bytes and error correction check bytes in the record and for multiplying all the data bytes and error correction check bytes, except for a second preselected set of the error correction check bytes, by a matrix of the form T<-(n+1)> in order to generate a second sub-set of CRC check bytes, and
means for combining the first and second sub-sets of CRC check bytes so as to generate the set of CRC check bytes.
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