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ATA REGISTERS SSD-HXXX(I)-3650 DATA SHEET
SILICONSYSTEMS PROPRIETARY
This document and the information contained within it is confidential and proprietary to SiliconSystems, Inc.
All unauthorized use and/or reproduction is prohibited.
DOCUMENT: 3650H-02DSR JUNE 17, 2008 PAGE 21
DRIVE/HEAD REGISTER
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 23: 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
10100000
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)