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11.51.1.10 SMART Return Status (Subcommand DAh)
This command is used to communicate the reliability status of the device to the host's request. 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,
C2h into the Cylinder High register.
If the device detects a Threshold Exceeded Condition, the device loads F4h into the Cylinder Low register, 2Ch into
the Cylinder High register.
11.51.1.11 SMART 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 save this data to the device's
non-volatile memory. 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 device's Sector Count Register before issuing this subcommand shall
cause the feature to be disabled. Disabling this feature does not preclude the device from saving attribute values to
non-volatile memory during some other normal operation such as during a power-on or power-off sequence or during
an error recovery sequence.
A value of F8h written by the host into the device's Sector Count Register before issuing this subcommand shall
cause this feature to be enabled. Any other non-zero value written by the host into this register before issuing this
subcommand is vender specific and will not change the current Automatic Off-Line Data Collection, but the device
may respond with the error code specified in Table 242 on the page.277
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Western Digital Hard Disk Drive OEM Specification
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