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During times that the SATA peripheral is in use, the SATASS supports the industry standard power
down modes (both Partial and Slumber low power modes) as provided within the SATA specification.
These modes allow for power savings by powering down part of the SERDES PHY and by providing
the ability to gate off the clocks to the link layer. The Port Power Control Module is used to enter and
exit this power down modes (that is power down mode is controlled at Port level) which may have the
normal functional clocks gated off.
NOTE: When SATA communication is in the idle state, that is, when no disk activity takes place,
the communication remains active with both the host and the device sending a logical
sync primitive and scrambled data at the speed negotiated continuously. For power
sensitive applications, the power consumed during the disk inactivity stage might be
undesirable and it might be a desired task to place the communication interface into an
electrical idle (Partial or Slumber) state until data transfer activity is needed in order to
conserve power.
16.2.10 Reset
The SATA controller reset is handled via PRCM. Please consult the PRCM document for details on
how to use the PRCM module. Other types of resets (HBA Reset, Port Reset, and Software Reset)
supported by the SATA controller are part of the AHCI specification. See the AHCI Standard
Specification 1.1 for details on HBA Reset, Port Rest, and Software Reset.
16.2.11 Interfacing to Single and Multiple Devices
The SATA controller supports dual HBA ports. This means that each HBA port can be used to interface
directly to a single SATA device or to multiple SATA Devices via a Port Multiplier. Note that on a
multiple target setup, the available bandwidth will be shared amongst all the attached devices.
Note that Port Multipliers and Power Supplies for external SATA devices, when needed, should be
furnished external to the device. No dedicated signals for controlling power and device detection are not
bonded out and usage of GPIO pins can be used to supplement this task. However, the controller
supports the capability to spin-up-attached devices independently.
16.2.11.1 Interfacing to a Single Device
If need to interface directly to a Single Device, there is no need of populating a Port Multiplier. The
software needs to ensure that the PMP field within the Command Header and the PM_PORT field of
the FIS be cleared at all times.
If the external SATA device is not Self Powered, it is the responsibility of the System Designer to
populate and furnish the right power supply needed. Consult the SATA Specification for details.
16.2.11.2 Interfacing to Multiple Devices
Interfacing to multiple devices is pretty much identical to interfacing with a single device except the
addition of a hardware Port Multiplier and initialization on software side. User software is required to
perform the additional task of detecting and configuring the PM prior to accessing the attached devices.
The user software is required to populate the Port Multiplier Port (PMP) field of the FIS in order to
select one of the fifteen devices that could be connected and accessed by the HBA. The details on this
are fully captured within the AHCI specification Version 1.1.
16.2.12 Initialization
Proper initialization of the HBA is required after power up to ensure proper operation of the SATA
controller peripheral. The initialization process starts by performing a write to one-time write only
registers (this initialization step is documented as Firmware initialization within the AHCI specification)
where the values programmed depend on the features that the applications support. Note that the
features that are enabled by the Firmware initialization are subsets of the features supported by the
SATA subsystem. This Firmware initialization is similar to what a PC BIOS does and allows the user to
enable/disable some features by using software.
SPRUGX9 – 15 April 2011
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Preliminary
© 2011, Texas Instruments Incorporated
Architecture
Serial ATA (SATA) Controller
1571
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