Hitachi Deskstar 7K500 Specifications page 127

If the device receives a Security Erase Unit command without a prior Security Erase Prepare command the device
aborts the security erase unit command.
This command disables the security mode feature (device lock function), however, the master password is still
stored internally within the device and may be reactivated later when a new user password is set. If you execute this
command when disabling the security mode feature (device lock function), the password sent by the host is NOT
compared with either the Master Password or the User Password. The device then erases all user data.
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Deskstar 7K500 Hard Disk Drive Serial ATA Addendum
118