Western Digital manual T13/2132-D Revision June 23 Device Address Packet Offset

T13/2132-D Revision 3 June 23, 2010

		Table 9 — Device Address Packet
Offset	Type	Description
0	Byte	Packet size in bytes. The value in this field shall be 16 (10h) or greater. If the packet size
		is less than 16 the request shall be rejected with CF = 1b and AH = 01h.
1	Byte	Reserved.
2	Byte	Number of blocks to transfer. This field shall contain a maximum value of 127 (7Fh). If
		this field is set to FFh, then the transfer buffer address shall be found at offset 10h, the
		number of blocks to transfer shall be found at offset 18h, and the transfer buffer at offset 4
		shall be ignored. If this field is set to 00h, then no data shall be transferred. If any other
		value is supplied, then the request shall be rejected with CF=1b and AH=01h
3	Byte	Reserved.
4	DWord	Address of host transfer buffer. This is the host buffer that Read/Write operations shall
		use to transfer the data. This is a 32-bit host address of the form Seg:Offset. If this field
		is set to FFFFh:FFFFh then the address of the transfer buffer shall be found at offset 10h.
8	QWord	Starting logical block address on the target device of the data to be transferred. This is a
		64-bit unsigned linear address. If the device supports LBA addressing this value should
		be passed unmodified. If the device does not support LBA addressing the routine making
		the INT 13h call shall convert this LBA to a CHS address using the current geometry in
		the following formula:
		LBA = (C1 * H0 + H1) * S0 + S1 = 1
		Where:
		C1 = Selected Cylinder Number
		H0 = Number of Heads (Maximum Head Number + 1)
		H1 = Selected Head Number
		S0 = Maximum Sector Number
		S1 = Selected Sector Number
		For ATA compatible devices with less than or equal to 15,482,880 logical sectors, the H0
		and S0 values are supplied by words 3 and 6 of the data returned as a result of an
		IDENTIFY DEVICE command.
10h	QWord	64-bit unsigned linear address of the host transfer buffer. This is the host buffer that
		Read/Write operations shall use to transfer the data if the data at offset 4 is set to
		FFFFh:FFFFh, or the data at offset 2 is set to FFh.
18h	DWord	Total number of blocks to transfer when the data at offset 2 is set to FFh
1Ch	DWord	Reserved.

Note 1 - The options described in table 1 allow a host to use a 7-bit transfer size with a 32 -bit or 64-bit memory address for the transfer buffer. Table 1 also allows a 32-bit transfer size in conjunction with a 64-bit address. A 32-bit transfer size shall not be used in conjunction with a 32-bit memory address.

16 Working Draft Enhanced Disk Drive - 4 (EDD-4)