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Cactus Technologies, Limited
Cactus Technologies Limited
-900 Series Industrial Grade SATA SSD Product Manual
v1.0
19
4.1.3.
Feature Register
This register provides information regarding features of the SSD that the host can utilize.
4.1.4.
Sector Count Register
This register contains the number of sectors of data requested to be transferred on a read or
write operation between the host and the SSD. If the value in this register is zero, a count of 256
sectors is specified. If the command was successful, this register is zero at command completion.
If not successfully completed, the register contains the number of sectors that need to be
transferred in order to complete the request.
4.1.5.
Sector Number (LBA 7-0) Register
This register contains the starting sector number or bits 7-0 of the Logical Block Address (LBA) for
any SSD data access for the subsequent command.
4.1.6.
Cylinder Low (LBA 15-8) Register
This register contains the low order 8 bits of the starting cylinder address or bits 15-8 of the Logical
Block Address.
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.