Hitachi 100GB 7200 RPM HTE721010G9SA00 User Manual

Travelstar E7K100 (Serial ATA) Hard Disk Drive Specification

41 

In Serial ATA, the host adapter contains a set of registers that shadow the contents of the traditional device regis-
ters, referred to as the Shadow Register Block. Shadow Register Block registers are interface registers used for 
delivering commands to the device or posting status from the device. About details, please refer to the Serial ATA 
Spec.

In the following cases, the host adapter sets the BSY bit in its shadow Status Register and then transmits a FIS to 
the device containing the new regster contents.

- Command register is written in the Shadow Register Block

- Device Control register is written in the Shadow Register Block with a change of state of the SRST bit

- COMRESET is requested

This specification uses the same naming conventions for the Command Block Registers as the ATA/ATAPI-7 stan-
dard. However, the register naming convention is different from that uses in the Serial ATA 1.0a specification. Fig-
ure 1 defines the corresponding of the register names used in this specification with those used in the Serial ATA 
1.0a specification.

Serial ATA register 

name

Register name in this 

specification when 

writing registers

Register name in this 

specification when 

reading registers

Features Feature 

current

Features (exp)

Feature previous

Sector count

Sector count current

Sector count HOB=0

Sector count (exp)

Sector count previous

Sector count HOB=1

Sector number

LBA low current

LBA low HOB=0

Sector number (exp)

LBA low previous

LBA low HOB=1

Cylinder low

LBA mid current 

LBA mid HOB=0

Cyliner low (exp)

LBA mid previous

LBA mid HOB=1

Cylinder high

LBA high current

LBA mid HOB=0

Cylinder high (exp)

LBA high previous

LBA mid HOB=1

Device/head

Device

Device

Command Command

N/A

Control

Device Control

N/A

Status N/A

Status

Error N/A

Error