Hitachi HDS721050CLA362 Specifications page 177

Cylinder High (HOB=1)
CCTO (Error, bit 0)
SE (Status, bit 5)
HITACHI Deskstar & CinemaStar 7K1000.B & Deskstar E7K1000 Hard Disk Drive specification
LBA (47:40) of the address of the first unrecoverable error.
CCTO bit shall be set to one if a Command Completion Time Limit Out error has
occurred.
SE (Stream Error) shall be set to one if an error has occurred during the execution
of the command and the RC bit is set to one. In this case the LBA returned in the
Sector Number registers shall be the address of the first sector in error, and the
Sector Count registers shall contain the number of consecutive sectors that may
contain errors. If the RC bit is set to one when the command is issued and a
UNC, IDNF, ABRT, or CCTO error occurs, the SE bit shall be set to one, the ERR
bit shall be cleared to zero, and the bits that would normally be set in the Error
register shall be set in the error log.
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