On Thu, Mar 16, 2017 at 9:31 AM, MRAB <pyt...@mrabarnett.plus.com> wrote: >> 3.2. If the carry bit from S1 is 1, the MSB of S1 and LSB of S0 are >> inverted. >> Points 2 and 3 are executed for all bytes, included in the calculation of >> the CRC - from the first byte after BEG up to and including byte END. >> 4. TR is loaded with 0 and point 3 is executed >> 5. TR is loaded with 0 and point 3 is executed >> 6. Byte S1 is transmitted >> 7. Byte S0 is transmitted >> > [snip] > Step 3 is a little unclear. > > Step 3.1 says to shift TR, but step 3.2 says to check the carry bit after > shifting S1, which is zero initially, therefore the carry bit will be clear, > therefore S1 and S0 won't have any bits inverted and will stay zero. >
I think probably "if the carry bit from TR is 1" would make this all make sense. Otherwise TR, which is the data payload, is completely ignored. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
