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June 23, 2010 T13/2132-D Revision 3
Working Draft Enhanced Disk Drive - 4 (EDD-4) 55
8.20.4.1 Offset 0-1 - I/O port base
This word is the 16-bit address in I/O space of the data register in the ATA Command Block. Any application that
provides a proprietary interface to the device may use this base address.
8.20.4.2 Offset 2-3 - control port base
This word is the 16-bit address in I/O space of the device control register. Any application that provides a
proprietary interface to the device may use this address.
8.20.4.3 Offset 4 - head prefix
The upper four bits of this byte shall be logically ORed with the head number, or upper four bits of the LBA, each
time the disk is addressed. It contains the ATA DEV bit and the LBA addressing bits that are preset, and makes
these functions transparent to any software using this extension. The LBA addressing bit is set for each disk
access and shall not be used to determine the LBA capability of the system. See the LBA translation enabled bit
described in clause 8.24.3.9.5 for system LBA capability.
8.20.4.4 Offset 5 - BIOS use only
BIOS use only.
8.20.4.5 Offset 6 - IRQ number
Each ATA channel requires an assigned Interrupt number. This byte identifies which IRQ is used by this device's
channel.
8.20.4.6 Offset 7 - READ/WRITE MULTIPLE command block count
If the device was configured to use the READ/WRITE MULTIPLE command, then this field shall contain the block
size of the transfer, in sectors, used by the BIOS.
10-11 Word BIOS selected hardware specific option flags
Bit Description
15:14 Reserved
13 48-bit LBA addressing enabled
12 HPA Active
11 Ultra DMA accessing enabled
10:9 Translation type
8 ATAPI device uses command packet interrupt
7 32-bit transfer mode
6 ATAPI device
5 Removable media
4 LBA translation enabled
3 CHS translation enabled
2 ATA READ/WRITE MULTIPLE accessing enabled
1 DMA accessing enabled
0 PIO accessing enabled
12-13 Word Reserved
14 Byte 30h, version level of this table.
15 Byte Checksum, 2's complement of the 8 bit unsigned sum of bytes 0-14
Table 25 — Device parameter table extension
Offset Type Description