Hitachi T7K250 - Deskstar - Hard Drive Specifications page 217

Upon receipt of the S.M.A.R.T. Disable Operations subcommand from the host, the device asserts BSY, disables
S.M.A.R.T. capabilities and functions, clears BSY, and asserts INTRQ.
After receipt of the device of the S.M.A.R.T. Disable Operations subcommand from the host, all other S.M.A.R.T.
subcommands—with the exception of S.M.A.R.T. Enable Operations—are disabled and invalid and will be aborted
by the device—including the S.M.A.R.T. Disable Operations subcommand—returning the error code as specified
in Table 137: "S.M.A.R.T. Error Codes" on page 212.
Any Attribute Values accumulated and saved to volatile memory prior to receipt of the S.M.A.R.T. Disable Opera-
tions command will be preserved in the device's Attribute Data Sectors. If the device is re-enabled, these Attribute
Values will be updated, as needed, upon receipt of a S.M.A.R.T. Read Attribute Values or a S.M.A.R.T. Save
Attribute Values command.
12.43.1.10 S.M.A.R.T. Return Status (subcommand DAh)
This command is used to communicate the reliability status of the device upon the request of the host. Upon receipt
of the SMART Return Status subcommand the device saves any updated Pre-failure type Attribute Values to the
reserved sector and compares the updated Attribute Values to the Attribute Thresholds.
If the device does not detect a Threshold Exceeded Condition, the device loads 4Fh into the Cylinder Low register
and C2h into the Cylinder High register.
If the device detects a Threshold Exceeded Condition, the device loads F4h into the Cylinder Low register and 2Ch
into the Cylinder High register.
12.43.1.11 S.M.A.R.T. Enable/Disable Automatic Off-line (subcommand DBh)
This subcommand enables and disables the optional feature that causes the device to perform the set of off-line data
collection activities that automatically collect attribute data in an off-line mode and then saves this data to the non-
volatile memory of the device. This subcommand may either cause the device to automatically initiate or resume
performance of its off-line data collection activities or cause the Automatic Off-line Data Collection feature to be
disabled.
A value of zero written by the host into the Sector Count register of the device before issuing this subcommand
causes the feature to be disabled. Disabling this feature does not preclude the device from saving attribute values to
nonvolatile memory during some other normal operation such as during a power-on or power-off sequence or dur-
ing an error recovery sequence.
A value of F8h written by the host into the Sector Count register of the device before issuing this subcommand
causes this feature to be enabled. Any other nonzero value written by the host into this register before issuing this
subcommand is vender specific and does not change the current Automatic Off-line Data Collection status, but the
device may respond with the error code specified in Table 137: "S.M.A.R.T. Error Codes" on page 212.
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