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Read Sector(s) (20h/21h)
Command Block Output Registers
Command Block Input Registers
Register
7
6
5
4
3
2
1
0
Register
7
6
5
4
3
2
1
0
Data
-
-
-
-
-
-
-
-
Data
-
-
-
-
-
-
-
-
Feature
-
-
-
-
-
-
-
-
Error
…See Below…
Sector Count
V
V
V
V
V
V
V
V
Sector Count
V
V
V
V
V
V
V
V
Sector Number
V
V
V
V
V
V
V
V
Sector Number
V
V
V
V
V
V
V
V
Cylinder Low
V
V
V
V
V
V
V
V
Cylinder Low
V
V
V
V
V
V
V
V
Cylinder High
V
V
V
V
V
V
V
V
Cylinder High
V
V
V
V
V
V
V
V
Device/Head
1
L
1
D
H
H
H
H
Device/Head
-
-
-
-
H
H
H
H
Command
0
0
1
0
0
0
0
R
Status
…See Below…
Error Register
Status Register
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
CRC UNC
0
IDN
0
ABT T0N AMN BSY RDY
DF
DSC DRQ COR IDX ERR
0
V
0
V
0
V
0
0
0
V
0
V
-
0
-
V
Table 189 Read Sector(s) Command (20h/21h)
The Read Sector(s) command reads one or more sectors of data from disk media, and then transfers the data from
the device to the host.
The sectors are transferred through the Data Register 16 bits at a time.
If an uncorrectable error occurs, the read will be terminated at the failing sector.
Output Parameters To The Device
Sector Count
The number of continuous sectors to be transferred. If zero is specified, then 256
sectors will be transferred.
Sector Number
The sector number of the first sector to be transferred. (L=0)
In LBA mode, this register contains LBA bits 0 – 7. (L=1)
Cylinder High/Low
The cylinder number of the first sector to be transferred. (L=0)
In LBA mode, this register contains LBA bits 8 – 15 (Low), 16 – 23 (High). (L=1)
H
The head number of the first sector to be transferred. (L=0)
In LBA mode, this register contains LBA bits 24 – 27. (L=1)
R
The retry bit, but this bit is ignored.
Input Parameters From The Device
Sector Count
The number of requested sectors not transferred. This will be zero, unless an
unrecoverable error occurs.
Sector Number
The sector number of the last transferred sector. (L=0)
In LBA mode, this register contains current LBA bits 0 – 7. (L=1)
Cylinder High/Low
The cylinder number of the last transferred sector. (L=0)
In LBA mode, this register contains current LBA bits 8 – 15 (Low), 16 – 23 (High). (L=1)
H
The head number of the last transferred sector. (L=0)
In LBA mode, this register contains current LBA bits 24 – 27. (L=1)
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Western Digital Ultrastar DC HC310 SATA Product Manual