Bitfields for AMD-645 UltraDMA/33 Extended Timing Control register:
Bit(s)	Description	)
 7	method for enabling UltraDMA mode on drive
	0 using "Set Feature" command
	1 using bit 6 of this register
 6	enable UltraDMA mode for drive
 5	UltraDMA transfer mode
	0 UltraDMA DMA mode
	1 UltraDMA PIO mode
 4-2	reserved (0)
 1-0	drive cycle time
	00 = 2T
	...
	11 = 5T
SeeAlso: #01011