Advanced Configuration and Power Interface Specification

ACPI Software Programming Model
Field
Firmware Waking
Vector
Byte
Length
Byte
Offset
Description
4 12 This field is superseded by the X_Firmware_Waking_Vector
field.
The 32-bit address field where OSPM puts its waking vector.
Before transitioning the system into a global sleeping state,
OSPM fills in this field with the physical memory address of an
OS-specific wake function. During POST, the platform firmware
first checks if the value of the X_Firmware_Waking_Vector field
is non-zero and if so transfers control to OSPM as outlined in
the X_Firmware_Waking_vector field description below. If the
X_Firmware_Waking_Vector field is zero then the platform
firmware checks the value of this field and if it is non-zero,
transfers control to the specified address.
On PCs, the wake function address is in memory below 1 MB
and the control is transferred while in real mode. OSPM’s wake
function restores the processors’ context.
For IA-PC platforms, the following example shows the
relationship between the physical address in the Firmware
Waking Vector and the real mode address the BIOS jumps to.
If, for example, the physical address is 0x12345, then the BIOS
must jump to real mode address 0x1234:0x0005. In general this
relationship is
Real-mode address =
Physical address>>4 : Physical address and 0x000F
Notice that on IA-PC platforms, A20 must be enabled when the
BIOS jumps to the real mode address derived from the physical
address stored in the Firmware Waking Vector.
Global Lock 4 16 This field contains the Global Lock used to synchronize access
to shared hardware resources between the OSPM environment
and an external controller environment (for example, the SMI
environment). This lock is owned exclusively by either OSPM or
the firmware at any one time. When ownership of the lock is
attempted, it might be busy, in which case the requesting
environment exits and waits for the signal that the lock has
been released. For example, the Global Lock can be used to
protect an embedded controller interface such that only OSPM
or the firmware will access the embedded controller interface at
any one time. See Section 5.2.10.1, “Global Lock,” for more
information on acquiring and releasing the Global Lock.
Flags 4 20 Firmware control structure flags. See Table 5-39 for a
description of this field.
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