Deskstar 7K250 Hard Disk Drive Specification
136
12.16 Read DMA Queued (C7h)
Table 76: Read DMA command (C8h/C9h)
This command executes in a similar manner to a READ DMA command. The device may perform a bus release or
it may execute the data transfer without performing a bus release if the data is ready to transfer.
If the device performs a bus release, the host shall reselect the device using the SERVICE command.
When the data transfer is begun, the device does not perform a bus release until the entire data transfer has been
completed.
Output parameters to the device
Feature
The number of sectors to be transferred. A value of 00h indicates that 256 sectors are to be
transferred.
Sector Count
Bits 7 - 3 (Tag) contain the Tag for the command being delivered.
Sector Number
Starting sector number or LBA address bits 7 - 0.
Cylinder High/Low
Starting cylinder number or LBA address bits 23 - 8.
H
Starting head number or LBA address bits 27 - 24
Input parameters from the device on bus release
Sector Count
Bits 7 - 3 (Tag) contain the Tag of the command being bus released.
Bit 2 (REL) is set to one.
Bit 1 (I/O) is cleared to zero.
Bit 0 (C/D) is cleared to zero.
Sector Number, Cylinder High/low, H
n/a.
SRV
Cleared to zero when the device performs a bus release. This bit is set to one when the
device is ready to transfer data.
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
1 1 0 0 0 1 1 1
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
V
V
0
V
0
V
0
V
0
V
0
V
-
0
-
V
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