1 NMRA packets from the computer to the PIC should consist of 8-bit bytes.
3 bits 7-1 contain the data to be sent to the track
4 bit 0 is 1 if the byte is the last in the packet and 0 otherwise
6 The first 14 data bits in the NMRA packet should be 1s.
7 (i.e. the first two complete bytes should be 11111110 11111110)
8 (packets beginning with some other sequence are reserved for non-NMRA messages)
11 most significant bit first