7   6   5   4   3   2   1   0   7   6   5   4   3   2   1   0
   +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+...+---+
00 | Fixed prefix 'C' (43h)        | Command flag                  | Payload   |
   +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+...+---+