>>>The checksum being the sum of all the data '1' s in the bytes of the string.
>>You sure?
>No - the book says "The checksum is the sum of the data (D0 to D7) contained
>in each data word from the first to the last data word before Checksum."
>The checksum is one byte long, so I assumed it would be the sum of all the
>data 1's - the data is typically 5 or 6 bytes long.
>
>Apologies for drifting slightly off topic
I hope *I'm* not being dense.. Are you sure they don't simply mean the sum
of all bytes up to the checksum, where the sum is continually wrapping and the
carry is discarded.. This is pretty common.