Bitfields for DDT indicators:
Bit(s)	Description	)
 15	reserved (0)
 14	second arbitration level exists
 13	first arbitration level exists
 12	serial interface is RS-422
 11	not address limited
 10	DMA channel used
 9	second arbitration level can be shared
 8	first arbitration level can be shared
 7-0	reserved (0)