WD Scorpio ML320S-AF2
Product Features
2679-771320-A00
RELEASED 4/7/11 (WD CONFIDENTIAL)
17
3.5
S.M.A.R.T. Command Transport (SCT)
The SCT Command Transport feature set provides a method for a host to send commands and data to
a device and for a device to send data and status to a host using log pages. Standard ATA commands
may be interspersed with SCT commands, but SCT commands cannot be nested. SCT commands that
do not require a subsequent data transfer operation are not interspersed with any ATA commands or
each other.
The SCT Command Transport feature set provides a method for a host to send commands and data to
a device and for a device to send data and status to a host using log pages. This capabilitility is used to
pass commands through a driver interface or a bridge where new or unknown commands may be
filtered and not passed to the drive. SCT is also used for issuing commands that require more than 8
parameter bytes. ATA8-ACS provides detailed information on the usage and capabilities of SCT. The
SCT feature set includes the following commands:
Write Same
Read/Write Long
Temperature Reporting
3.5.1
Write Same
The Write Same command allows the host to erase the media, or write a pattern repeatedly across the
media, with a minimum of data transfer from the host. The host can clear the entire media to zeros or
a specific pattern by sending this command with the pattern as a parameter—no data transfer is
necessary. Write Same can write the entire media, or just a portion of the media. The host can monitor
the progress of the Write Same by issuing SCT Status requests. This frees the host system to do other
tasks while the media is being cleared.
3.5.2
Read/Write Long
The function performed by the Long Sector Access command is based on the obsolete ATA READ
LONG/WRITE LONG capability, and has been extended beyond 28-bit addressing. The Long Sector
data format for both reads and writes is two blocks long (i.e., each block is 512 bytes long). The first
block contains the user data. The second data block contains the error correction and detection bytes.
The remainder of the second block should contain zeros. Once the SCT command has been issued and
the status response indicates that the device is ready to transfer data, log page E1h should be read or
written to transfer the data. Long Sector Access commands cause a forced unit access to occur.
3.5.3
Temperature Reporting
The SCT Temperature Reporting (SCT TR) feature allows a host system to access temperature
information in the drive. This information can been used to control fans or adjust the usage of various
system components to keep the drive within its normal operating temperature. Applications include
Enterprise, Laptop, Desktop and Consumer Electronics. SCT TR reports the maximum and minimum
sustained operating limits, warning level limits, and drive damage limits. In addition to reporting the
limits, SCT TR returns the current drive temperature (a temperature history which the host can use to
predict heating or cooling trends) and the maximum temperature acheived during the lifetime of the
drive as well as the highest temperature achieved since the power was applied to the drive. Detailed
information on this capability can be found in ATA8-ACS.
