Functional Description
196 Datasheet
5.16.10 SATA LED
The SATALED# output is driven whenever the BSY bit is set in any SATA port. The
SATALED# is an active-low open-drain output. When SATALED# is low, the LED should
be active. When SATALED# is high, the LED should be inactive.
5.16.11 AHCI Operation
The PCH provides hardware support for Advanced Host Controller Interface (AHCI), a
programming interface for SATA host controllers developed through a joint industry
effort. AHCI defines transactions between the SATA controller and software and enables
advanced performance and usability with SATA. Platforms supporting AHCI may take
advantage of performance features such as no master/slave designation for SATA
devices—each device is treated as a master—and hardware assisted native command
queuing. AHCI also provides usability enhancements such as Hot-Plug. AHCI requires
appropriate software support (such as, an AHCI driver) and for some features,
hardware support in the SATA device or additional platform hardware.
The PCH supports all of the mandatory features of the Serial ATA Advanced Host
Controller Interface Specification, Revision 1.2 and many optional features, such as
hardware assisted native command queuing, aggressive power management, LED
indicator support, and Hot-Plug through the use of interlock switch support (additional
platform hardware and software may be required depending upon the implementation).
Note: For reliable device removal notification while in AHCI operation without the use of
interlock switches (surprise removal), interface power management should be disabled
for the associated port. See Section 7.3.1 of the AHCI Specification for more
information.
5.16.12 SGPIO Signals
The SGPIO signals, in accordance to the SFF-8485 specification, support per-port LED
signaling. These signals are not related to SATALED#, which allows for simplified
indication of SATA command activity. The SGPIO group interfaces with an external
controller chip that fetches and serializes the data for driving across the SGPIO bus.
The output signals then control the LEDs. This feature is only valid in AHCI/RAID mode.
5.16.12.1 Mechanism
The enclosure management for SATA Controller 1 (Device 31: Function 2) involves
sending messages that control LEDs in the enclosure. The messages for this function
are stored after the normal registers in the AHCI BAR, at Offset 580h bytes for the PCH
from the beginning of the AHCI BAR as specified by the EM_LOC global register
(Section 14.4.1.6).
Software creates messages for transmission in the enclosure management message
buffer. The data in the message buffer should not be changed if CTL.TM bit is set by
software to transmit an update message. Software should only update the message
buffer when CTL.TM bit is cleared by hardware otherwise the message transmitted will
be indeterminate. Software then writes a register to cause hardware to transmit the
message or take appropriate action based on the message content. The software
should only create message types supported by the controller, which is LED messages
for the PCH. If the software creates other non LED message types (such as, SAF-TE,
SES-2), the SGPIO interface may hang and the result is indeterminate.
During reset all SGPIO pins will be in tri-state. The interface will continue to be in tri-
state after reset until the first transmission occurs when software programs the
message buffer and sets the transmit bit CTL.TM. The SATA Host controller will initiate
the transmission by driving SCLOCK and at the same time drive the SLOAD to ‘0’ prior
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