Deskstar 7K250 Hard Disk Drive Specification
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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
7654321 0 76543 21 0
CRC UNC 0 IDN 0 ABT T0N AMN BSY RDY DF DSC DRQ COR IDX ERR
VV0V0V0 V 0V0V- 0- V
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