Address Offset Feature - Hitachi DK23EB - Travelstar Series 20 GB Hard Drive Specifications

The Set Max Unlock command changes the device from the Set Max Locked mode to the
Set Max Unlocked mode.
The Set Max Freeze Lock command allows the host to disable the Set Max commands (including Set
Max Unlock) until the next power cycle. When this command is accepted the device is in the
Set Max Frozen mode.

6.3.2.10.2 Address Offset Feature

Computer systems perform initial code booting by reading from a predefined address on a disk drive.
To allow an alternate bootable operating system to exist in a reserved are on disk drive, Address Offset
Feature provides a Set Feature function to temporarily offset the drive address space. The offset address
space wraps around so that the entire disk drive address space remains addressable in offset mode. The
Set Max pointer is set to the end of the reserved area to protect the data in the user area when operating in
offset mode. This protection can be removed by an Set Max Address command to move the Set Max pointer
to the end of the drive.
Set Feature Command Subcommand code 09h "Enable Address Offset Mode command" offsets address
Cylinder 0, Head 0, Sector 1, LBA 0, to the start of a non-volatile reserved area established using the Set
Max Address Command. The offset condition is cleared by Set Feature Command Subcommand 89h
"Disable Address Offset Mode", Software Reset, Hardware Reset or Power on Reset. Upon entering offset
mode the capacity of the drive returned in the Identify Device data is the size of the former reserved area. A
subsequent Set Max Address Command using the address returned by Read Max Address Command
allows access to the entire drive. Addresses wrap so the entire drive remains addressable.
If a non-volatile reserved area has not been established before the device receives a Set Features Enable
Address Offset Mode command, the command fails with Abort error status.
Disable Address Offset Mode removes the address offset and sets the size of the drive reported by the
Identify Device command back to the size specified in the last non-volatile Set Max Address command.
Identify Device Word 83 bit 7.indicates the device supports the Set Features Address Offset Mode.
Identify Device Word 86 bit 7 indicates the device is in address offset mode.
K6602743
Rev.2
02.12.'02
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