K6610170
Rev.2
Dec 22, 2004
- 88 -
7.5.23. Read Sectors [20h, 21h]
Task
File
Registers
7 6 5 4 3 2 1 0
Command
20h or 21h
LBA High
L = 0: Cylinder number bit 15 - 8
L = 1: 28-bit LBA address bit 23 - 16
LBA Mid
L = 0: Cylinder number bit 7 - 0
L = 1: 28-bit LBA address bit 15 - 8
LBA Low
L = 0: Sector number
L = 1: 28-bit LBA address bit 7 - 0
Device/Head
X
L
X
DRV L = 0: Head Number
L = 1:28-bit LBA
address bit 27-24
Sector Count
Sector Count
Features
XX
This command reads sectors as specified in the Sector Count Register. The read operation begins at the
sector specified in the LBA High, LBA Mid and LBA Low Registers. DRQ is set prior to data transfer
regardless of the presence or absence of an error condition. At command completion, the Command Block
Registers contain the 28-bit LBA address or cylinder/head/sector numbers of the last sector read. If an error
occurs, the read terminates at the sector where the error occurred. The Command Block Registers contain
the 28-bit LBA address or the cylinder/head/sector numbers where the error occurred.
7.5.24. Read Sectors EXT [24h]
Task
File
Register
7 6 5 4 3 2 1 0
Command 24h
Feature Previous
setting
XX
Current
setting
XX
LBA High
Previous setting
LBA bit 47 - 40
Current setting
LBA bit 23 - 16
LBA Mid
Previous setting
LBA bit 39 - 32
Current setting
LBA bit 15 - 8
LBA Low
Previous setting
LBA bit 31 - 24
Current setting
LBA bit 7 - 0
Sector Count
Previous setting
Sector Count bit 15 - 8
Current setting
Sector Count bit 7 - 0
Device
X 1 X
DEV
X X X X
The READ SECTORS EXT command reads sectors as specified in the Sector Count Register. The read
operation begins at the sector specified in the LBA High, LBA Mid and LBA Low Registers. DRQ is set prior
to data transfer regardless of the presence or absence of an error condition. At command completion, the
Command Block Registers contain the 48-bit LBA address of the last sector read. If an error occurs, the read
terminates at the sector where the error occurred. The Command Block Registers contain the 48-bit LBA
address where the error occurred.