Silicon Image SiliconDrive SSD-DXXX(I)-4210 - Manual (Page 43)

ATA R EGISTERS SSD-D XXX (I)-4210 D ATA S HEET
S ILICON S YSTEMS P ROPRIETARY
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4210D-03DSR P AGE 34 F EBRUARY 2, 2009
D RIVE /H EAD R EGISTER
The Drive/Head register is used by the host and the device to select the type
of addressing (CHS or LBA), the drive letter, and either bits 3-0 of the head
number in CHS mode or logical block number bits 27-24 in LBA mode.
The Drive/Head register is used by the host to specify one of a pair of ATA
drives present in the platform.
Table 21: Drive/Head Register
Operation D
7
D
6
D
5
D
4
D
3
D
2
D
1
D
0
Read/Write 1 LBA 1 DRV HS3
LBA27
HS2
LBA26
HS1
LBA25
HS0
LBA24
Default
Value 1 0 1 0 0 0 0 0
Bit(s) Description
6
LBA.
Selects between CHS (0) and LBA (1) addressing mode.
4
Drive Address (DRV).
Indicates the drive number selected by the
host, either 0 or 1.
3-0 HS3 to 0. Indicates bits 3-0 of the head number in CHS addressing
mode or LBA bits 27-24 in LBA mode.
• CHS to LBA conversion: LBA = (C x HpC + H) x SpH + S -1
• LBA to CHS conversion:
¶
C = LBA/(HpC x SpH)
¶
H = (LBA/SpH) mod (HpC)
¶
S = (LBA mod(SpH)) + 1
...where:
¶
C is the cylinder number
¶
H is the head number
¶
S is the sector count
¶
HpC is the head count per cylinder count
¶
SpH is the sector count per head count (track)