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LSF CRC check rewording 

thanks, edgetriggered
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Wojciech Kaczmarski 2024-10-18 19:52:33 +03:00
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M17_spec.pdf
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M17_spec.tex
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@ -586,7 +586,7 @@ M17 uses a non-standard version of 16-bit CRC with polynomial $x^{16} + x^{14} +
As M17's native bit order is most significant bit first, neither the input nor the output of the CRC algorithm gets reflected.
The input to the CRC algorithm consists of 28 bytes: 6-byte DST, 6-byte SRC, 2-byte TYPE and 14-byte META field. For data integrity verification, the received 28 bytes of LSF can be appended with CRC value. The CRC algorithm returns zero if the data is valid.
The CRC field enables verification of the other 28 bytes forming the LSF: 6-byte DST, 6-byte SRC, 2-byte TYPE, and 14-byte META fields. Data integrity of an LSF frame is established by computing the CRC of the first 28 bytes and storing the resulting checksum in the trailing 2-byte CRC field, which can be compared by a recipient after repeating the same checksum process. Alternatively, a CRC computed over the entire 30-byte LSF frame, including a valid CRC field, will always equal zero.
The test vectors in the following table are calculated by feeding the given message to the CRC algorithm.