Fujitsu MHV2100BH, MHV2120BH Software settings preservation, Comreset preservation requirements

6.1 Reset and Diagnosis

6.1.2.1 Software settings 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 reservation 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 (refer to Section 5.3.2 (28)). If a device supports software settings preservation, the feature shall be enabled by default.

6.1.2.2 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.

•INITIALIZE DEVICE PARAMETERS

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Device settings established with the INITIALIZE DEVICE PARAMETERS command.

Power Management Feature Set Standby Timer

The Standby timer used in the Power Management feature set.

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.

•SECURITY FREEZE LOCK

The Frozen mode setting established by the SECURITY FREEZE LOCK command.

•SECURITY UNLOCK

The unlock counter that is decremented as part of a failed SECURITY UNLOCK command attempt.

C141-E224 6-5