5.3 Host Commands
Table 5.9 Features Field values (subcommands) and functions (3/3)
Features Field | Function |
X’DA’ | SMART RETURN STATUS: |
| When the device receives this subcommand, it saves the current device attribute |
| values. Then the device compares the device attribute values with guarantee |
| failure threshold values. If there is an attribute value exceeding the threshold, |
| F4h and 2Ch are loaded into the Cylinder Low and Cylinder High field. If there |
| are no attribute values exceeding the thresholds, 4Fh and C2h are loaded into the |
| Cylinder Low and Cylinder High field. After the settings for the Cylinder Low |
| and Cylinder High field have been determined, the device transfers the RegDH. |
X’DB’ | SMART ENABLE/DISABLE AUTO |
| This sets automatic |
| Count field specification ≠ 00h) or disabled (when the Sector Count field |
| specification = 00) state. This setting is preserved whether the drive’s |
| power is switched on or off. |
| If 24 hours have passed since the power was switched on, or since the last |
| time that |
| without relation to any command from the host computer. |
The host must regularly issue the SMART READ DATA subcommand (Features field = D0h), SMART SAVE ATTRIBUTE VALUES subcommand (Features field
=D3h), or SMART RETURN STATUS subcommand (Features field = DAh) to save the device attribute value data on a medium.
Alternative, the device must issue the SMART
The host can predict failures in the device by periodically issuing the SMART RETURN STATUS subcommand (Features field = DAh) to reference the Cylinder Low and Cylinder High field.
If an attribute value is below the guarantee failure threshold value, the device is about to fail or the device is nearing the end of its life. In this case, the host recommends that the user quickly backs up the data.