Hitachi IC25N040ATMR04-0 - Travelstar 40GB Laptop Hard Drive 9.5mm 2.5 Inch Notebook HDD Specifications page 175

The Sector Count register shall be set to specify the feature to be enabled or disabled:
Sector Count
00h Disable Automatic Off-line
01h Disable Off-line Read Scanning
F8h Enable Automatic Off-line
F9h Enable Off-line Read Scanning
A value of zero 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 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, during a power-off sequence, or during an error recovery sequence.
A value of one 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 disabled. The Device does not 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 (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 nonzero 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 121: "S.M.A.R.T. Error Codes" on page 175.
Feature Description
Travelstar 80GN Hard Disk Drive Specification
165