Femto Slider; Command Transport (Sct); Write Same; Read/Write Long - Western Digital caviar blue xl500s Technical Reference Manual

XL500S
a same cylinder position for a long time, the PWL control engine initiates forced seeks so that
disk lubricant maintains an even distribution and does not become depleted. This feature
ensures reliability for applications that perform a high incidence of read/write operations at the
same physical location on the disk.
3.7

Femto Slider

These drives incorporate the femto slider form factor in which the read/write head is mounted
on the small, lightweight femto slider which allows the head to move more quickly from track to
track on the disk. WD's femto heads enhance tracking and increase shock tolerance,
producing a highly stable high-density drive platform.
3.8 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

3.8.1
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.
3.8.2
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.
3.8.3
The SCT Temperature Reporting (SCT TR) feature allows a host system to access
temperature information in the drive. The S.M.A.R.T. temperature value is reported within
±3°C of the base casting temperature. This information can been used to control fans or
adjust the usage of various system components to keep the drive within its normal operating
2679-701211-A06
Write Same
Read/Write Long
Temperature Reporting
RELEASED 10/21/10 (WD CONFIDENTIAL)
Product Features
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