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4.1.7.
Cylinder High (LBA 23-16) Register
This register contains the high order bits of the starting cylinder address or bits 23-16 of the
Logical Block Address.
4.1.8.
Drive/Head (LBA 27-24) Register
The Drive/Head register is used to select the drive and head. It is also used to select LBA
addressing instead of cylinder/head/sector addressing. The bits are defined as follows:
D7
D6
D5
D4
D3
D2
D1
D0
1
LBA
1
DRV
HS3
HS2
HS1
HS0
Bit 7
This bit is set to 1.
Bit 6
LBA is a flag to select either Cylinder/Head/Sector (CHS) or Logical Block Address Mode (LBA).
When LBA=0, Cylinder/Head/Sector mode is selected. When LBA=1, Logical Block Address is
selected. In Logical Block Mode, the Logical Block Address is interpreted as follows:
LBA07-LBA00: Sector Number Register D7-D0.
LBA15-LBA08: Cylinder Low Register D7-D0.
LBA23-LBA16: Cylinder High Register D7-D0.
LBA27-LBA24: Drive/Head Register bits HS3-HS0.
Bit 5
This bit is set to 1.
Bit 4 (DRV)
DRV is the drive number. This should always be set to 0.
Bit 3 (HS3)
When operating in the Cylinder, Head, Sector mode, this is bit 3 of the head number. It
is Bit 27 in the Logical Block Address mode.
Bit 2 (HS2)
When operating in the Cylinder, Head, Sector mode, this is bit 2 of the head number. It
is Bit 26 in the Logical Block Address mode.
Bit 1 (HS1)
When operating in the Cylinder, Head, Sector mode, this is bit 1 of the head number. It
is Bit 25 in the Logical Block Address mode.
Bit 0 (HS0)
When operating in the Cylinder, Head, Sector mode, this is bit 0 of the head number. It
is Bit 24 in the Logical Block Address mode.
4.1.9.
Status Registers
These registers return the status when read by the host. Reading the Status register does
clear a pending interrupt while reading the Auxiliary Status register does not. The meaning
of the status bits are described as follows:
D7
D6
D5
D4
D3
D2
D1
D0
BUSY
RDY
DWF
DSC
DRQ
CORR
0
ERR
Cactus Technologies Limited
Commercial Grade -250SH Series SSD Product Manual
v2.1
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