Functional Description
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 400h bytes for ICH10
from the beginning of the AHCI BAR as specified by the EM_LOC global register
(Section 14.4.1.8).
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 ICH10. If the software creates other non LED message types (e.g. SAF-TE, SES-2),
the SGPIO interface may hang and the result is indeterminate.
During reset all SGPIO pins will be in tri-state state. The interface will continue to be in
tri-state 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 to the actual bit stream transmission. The Host will drive SLOAD low for at
least 5 SCLOCK then only start the bit stream by driving the SLOAD to high. SLOAD will
be driven high for 1 SCLOCK follow by vendor specific pattern that is default to “0000”
if software has yet to program the value. A total of 18-bit stream from 6 ports (Port0,
Port1, Port2, Port3, Port4 and Port5) of 3-bit per port LED message will be transmitted
on SDATAOUT0 pin after the SLOAD is driven high for 1 SCLOCK. Only 2 ports (port4
and port5) of 6 bit total LED message follow by 12 bits of tri-state value will be
transmitted out on SDATAOUT1 pin.
All the default LED message values will be high prior to software setting them, except
the Activity LED message that is configured to be hardware driven that will be
generated based on the activity from the respective port. All the LED message values
will be driven to ‘1’ for the port that is unimplemented as indicated in the Port
Implemented register regardless of the software programmed value through the
message buffer.
There are 2 different ways of resetting ICH SGPIO interface, asynchronous reset and
synchronous reset. Asynchronous reset is caused by platform reset to cause the SGPIO
interface to be tri-state asynchronously. Synchronous reset is caused by setting the
CTL.RESET bit, clearing the GHC.AE bit or HBA reset, where Host Controller will
complete the existing full bit stream transmission then only tri-state all the SGPIO pins.
After the reset, both synchronous and asynchronous, the SGPIO pins will stay tri-
stated.
Note:
ICH Host Controller does not ensure to cause the target SGPIO device or controller to
be reset. Software is responsible to keep ICH SGPIO interface in tri-state stated for 2
second in order to cause a reset on the target of the SGPIO interface.
Datasheet
185
INTEL [ INTEL ]
