Hitachi HTS421212H9AT00 - Travelstar 120 GB Hard Drive Specifications page 190

the off-line data collection activities which is initiated by the S.M.A.R.T. Execute Off-line Immediate (Subcom-
mand D4h) or automatically if the off-line read scanning feature is disabled.
A value of F8h written by the host into the device's Sector Count register before issuing this subcommand shall
cause the automatic Off-line data collection feature to be enabled.
A value of F9 written by the host into the device's Sector Count register before issuing this subcommand shall
cause the off-line read scanning feature to be enabled. The Device perform the off-line read scanning at the off-line
data collection activities which is initiated by the S.M.A.R.T. Execute Off-line Immediate (Subcommand D4h)
even if the automatic off-line feature is disabled.
Any other non-zero value written by the host into this register before issuing this subcommand is vendor specific
and will not change the current Automatic Off-Line Data Collection and Off-line Read Scanning status. However,
the device may respond with the error code specified in Table 132: "S.M.A.R.T. Error Codes" on page 187.
Travelstar 4K120 Hard Disk Drive Specification
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