Hitachi HDS721050CLA362 Specifications page 97

Once the key sector has been issued, if the Function Code was 0002h or 0102h and the TF Data indicates that
the drive is ready to receive data, log page E1h should be written to transfer the data.
This command can change the Segment Initialized Flag. If the command writes all the user addressable sectors
and completes without encountering an error or being aborted, then the ―Segment Initialized Flag‖ (bit 0 of the
Status Flags in the SCT Status. See0) shall be set to 1. A write to any user addressable sector on the drive
(except another complete write all), shall cause the Segment Initialized Flag to be cleared. Reallocations as a
result of reading data (foreground or background) do not clear the Segment Initialized Flag.
HITACHI Deskstar & CinemaStar 7K1000.B & Deskstar E7K1000 Hard Disk Drive specification
93