<data> Ascii hex representation of the NAK reason code (for
NAK response code), contents, or the requested data
(for ACK or interim ACK response codes). Some ACKs
and interim ACKs do not return any data, in which case
<datasz> will be zero.
<crc16> Four ascii hex digits representing the 16-bit CRC of all
encoded bytes up to, but not including the CRC. Note
that if the host includes the CRC value within the CRC
calculation, then the result will always be zero for
uncorrupted data.
<cr> The end of line. This is always present.
The CRC calculation is a standard 16-bit CRC (a proper CRC, not a
checksum). The CRC, combined with the ASCII hex encoding
technique, and including <datasz> as part of the protocol, gives a very
high degree of confidence that missing, extraneous, or corrupted
characters within commands or responses will be detected. There is
very little processing overhead in producing such CRCs. Please see the
example software for routines that provide the necessary CRC
calculations.
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