Advanced Configuration and Power Interface Specification

ACPI Hardware Specification
Device Idle
Timers
Device
Traps
Legacy Only Event Logic
ACPI/Legacy Event Logic
ACPI Only Event Logic
ACPI/Legacy Generic Control Features
ACPI/Legacy Fixed Control Features
GLBL STBY
Timer
SCI_EN
SMI Arbiter
SMI#
PWRBTN
LID
User
Interface
0
Dec
1
SCI Arbiter
SCI#
THRM
Thermal
Logic
Sleep/Wake
State machine
DOCK
STS_CHG
RI
Hardware
Events
RTC
SMI Events
SCI/SMI Events
Wake-up Events
Power Plane
Control
Generic Space
CPU Clock
Control
PM Timer
Figure 4-11 Example Event Structure for a Legacy/ACPI Compatible Event Model
This example logic illustrates the event model for a sample platform that supports both legacy and
ACPI event models. This example platform supports a number of external events that are powerrelated
(power button, LID open/close, thermal, ring indicate) or Plug and Play-related (dock, status
change). The logic represents the three different types of events:
OS Transparent Events
These events represent OEM-specific functions that have no OS support and use
software that can be operated in an OS-transparent fashion (that is, SMIs).
Interrupt Events
These events represent features supported by ACPI-compatible operating systems, but
are not supported by legacy operating systems. When a legacy OS is loaded, these
events are mapped to the transparent interrupt (SMI# in this example), and when in
ACPI mode they are mapped to an OS-visible shareable interrupt (SCI#). This logic is
represented by routing the event logic through the decoder that routes the events to the
SMI# arbiter when the SCI_EN bit is cleared, or to the SCI# arbiter when the SCI_EN
bit is set.
Hardware events
These events are used to trigger the hardware to initiate some hardware sequence such
as waking, resetting, or putting the machine to sleep unconditionally.
In this example, the legacy power management event logic is used to determine device/system
activity or idleness based on device idle timers, device traps, and the global standby timer. Legacy
power management models use the idle timers to determine when a device should be placed in a
low-power state because it is idle—that is, the device has not been accessed for the programmed
amount of time. The device traps are used to indicate when a device in a low-power state is being
accessed by OSPM. The global standby timer is used to determine when the system should be
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