sherzaad:
2. Start and End of Frame (0x01, 0x04): are they SOLELY used for just that ie these values are never present within the frame?
looks like byte stuffing is being used, i.e.
FOR SERIAL TRANSMISSION CHARACTERS 01H, 04H, 10H, 11H AND 13H CONTAINED IN THE DATA ARE CONVERTED TO CHARACTER 10H FOLLOWING THE FORBIDDEN CHARACTER