Hitachi 7K1000C User Manual
Hitachi hard disk drive specifications
76
9.16 Software Setting Preservation
When a device is enumerated, software will configure the device using SET FEATURES and other commands.
These software settings are often preserved across software reset but not necessarily across hardware reset.
In Parallel ATA, only commanded hardware resets can occur, thus legacy software only reprograms settings that
are cleared for the particular type of reset it has issued. In Serial ATA, COMRESET is equivalent to hard reset
and a non-commanded COMRESET may occur if there is an asynchronous loss of signal. Since COMRESET
is equivalent to hardware reset, in the case of an asynchronous loss of signal some software settings may be
lost without legacy software knowledge. In order to avoid losing important software settings without legacy
driver knowledge, the software settings preservation ensures that the value of important software settings is
maintained across a COMRESET. Software settings preservation may be enabled or disabled using SET
FEATURES with a subcommand code of 06h. If a device supports software settings preservation, the feature
shall be enabled by default.
These software settings are often preserved across software reset but not necessarily across hardware reset.
In Parallel ATA, only commanded hardware resets can occur, thus legacy software only reprograms settings that
are cleared for the particular type of reset it has issued. In Serial ATA, COMRESET is equivalent to hard reset
and a non-commanded COMRESET may occur if there is an asynchronous loss of signal. Since COMRESET
is equivalent to hardware reset, in the case of an asynchronous loss of signal some software settings may be
lost without legacy software knowledge. In order to avoid losing important software settings without legacy
driver knowledge, the software settings preservation ensures that the value of important software settings is
maintained across a COMRESET. Software settings preservation may be enabled or disabled using SET
FEATURES with a subcommand code of 06h. If a device supports software settings preservation, the feature
shall be enabled by default.
9.16.1
COMRESET Preservation Requirements
The software settings that shall be preserved across COMRESET are listed below. The device is only required
to preserve the indicated software setting if it supports the particular feature/command the setting is associated
with.
to preserve the indicated software setting if it supports the particular feature/command the setting is associated
with.
INITIALIZE DEVICE PARAMETERS: Device settings established with the INITIALIZE DEVICE
PARAMETERS command.
PARAMETERS command.
Power Management Feature Set Standby Timer: The Standby timer used in the Power Management
feature set.
feature set.
Read/Write Stream Error Log: The Read Stream Error Log and Write Stream Error Logs (accessed using
READ LOG EXT and WRITE LOG EXT).
READ LOG EXT and WRITE LOG EXT).
Security mode state: The security mode state established by Security Mode feature set commands (refer
to section 6.13 of the ATA/6 specification). The device shall not transition to a different security mode state
based on a COMRESET. For example, the device shall not transition from the SEC5: Unlocked / not
Frozen state to state SEC4: Security enabled / Locked when a COMRESET occurs, instead the device shall
remain in the SEC5: Unlocked / not Frozen state.
to section 6.13 of the ATA/6 specification). The device shall not transition to a different security mode state
based on a COMRESET. For example, the device shall not transition from the SEC5: Unlocked / not
Frozen state to state SEC4: Security enabled / Locked when a COMRESET occurs, instead the device shall
remain in the SEC5: Unlocked / not Frozen state.
SECURITY FREEZE LOCK: The Frozen mode setting established by the SECURITY FREEZE LOCK
command.
command.
SECURITY UNLOCK: The unlock counter that is decremented as part of a failed SECURITY UNLOCK
command attempt.
command attempt.
SET ADDRESS MAX (EXT): The maximum LBA specified in SET ADDRESS MAX or SET ADDRESS
MAX EXT.
MAX EXT.
SET FEATURES (Write Cache Enable/Disable): The write cache enable/disable setting established by the
SET FEATURES command with subcommand code of 02h or 82h.
SET FEATURES command with subcommand code of 02h or 82h.
SET FEATURES (Set Transfer Mode): PIO, Multiword, and UDMA transfer mode settings established by
the SET FEATURES command with subcommand code of 03h.
the SET FEATURES command with subcommand code of 03h.
SET FEATURES (Advanced Power Management Enable/Disable): The advanced power management
enable/disable setting established by the SET FEATURES command with subcommand code of 05h or 85h.
The advanced power management level established in the Sector Count register when advanced power
management is enabled (SET FEATURES subcommand code 05h) shall also be preserved.
enable/disable setting established by the SET FEATURES command with subcommand code of 05h or 85h.
The advanced power management level established in the Sector Count register when advanced power
management is enabled (SET FEATURES subcommand code 05h) shall also be preserved.
SET FEATURES (Read Look-Ahead): The read look-ahead enable/disable setting established by the SET
FEATURES command with subcommand code of 55h or AAh.
FEATURES command with subcommand code of 55h or AAh.
SET FEATURES (Reverting to Defaults): The reverting to power-on defaults enable/disable setting
established by the SET FEATURES command with a subcommand code of CCh or 66h.
established by the SET FEATURES command with a subcommand code of CCh or 66h.
SET MULTIPLE MODE: The block size established with the SET MULTIPLE MODE command.