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166 AMD Geode™ SC2200 Processor Data Book
Core Logic Module
32580B
6.2.9 Power Management Logic
The Core Logic module integrates advanced power man-
agement features including idle timers for common system
peripherals, address trap registers for programmable
address ranges for I/O or memory accesses, four program-
mable general purpose external inputs, clock throttling with
automatic speedup for the GX1 clock, software GX1 stop
clock, 0V Suspend/Resume with peripheral shadow regis-
ters, and a dedicated serial bus to/from the GX1 module
providing power management status.
The Core Logic module is ACPI (Advanced Configuration
Power Interface) compliant. An ACPI-compliant system is
one whose underlying BIOS, device drivers, chipset and
peripherals conform to revision 1.0 of the ACPI specifica-
tion. The Core Logic also supports Advanced Power Man-
agement (APM).
The SC2200 provides the following support of ACPI states:
• CPU States: C0, C1, and C3.
• Sleep States:
— SL1/SL2 - ACPI S1 equivalent.
— SL3 - ACPI S3 equivalent.
— SL4 - ACPI S4 equivalent.
— SL5 - ACPI S5 equivalent.
• General Purpose Events: Fully programmable GPE0
Event Block registers.
• Wakeup Events: Supported through GPWIO[2:0] which
are powered by standby voltage and generate SMIs.
See registers at F1BAR1+I/O Offset 0Ah and
F1BAR1+I/O Offset 12h. Also see Section 5.6 "System
Wakeup Control (SWC)" on page 123 and Table 6-5
"Wakeup Events Capability" on page 167.
SC2200 device power management is highly tuned for low
power systems. It allows the system designer to implement
a wide range of power saving modes using a wide range of
capabilities and configuration options.
SC2200 controls the following functions directly:
• The system clocks.
• Core processor power states.
• Wakeup/resume event detection, including general
purpose events.
• Power supply and power planes.
It also supports systems with an external micro controller
that is used as a power management controller.
6.2.9.1 CPU States
The SC2200 supports three CPU states: C0, C1 and C3
(the Core Logic C2 CPU state is not supported). These
states are fully compliant with the ACPI specification, revi-
sion 1.0. These states occur in the Working state only
(S0/G0). They have no meaning when the system transi-
tions into a Sleep state. For details on the various Sleep
states, see Section 6.2.9.2 "Sleep States" on page 167.
C0 Power State - On
In this state the GX1 module executes code. This state has
two sub-states: Full Speed or Throttling; selected via the
THT_EN bit (F1BAR1+I/O Offset 00h[4]).
C1 Power State - Active Idle
The SC2200 enters the C1 state, when the Halt Instruction
(HLT) is executed. It exits this state back to the C0 state
upon an NMI, an unmasked interrupt, or an SMI. The Halt
instruction stops program execution and generates a spe-
cial Halt bus cycle. (See “Usage Hints” on page 169.)
Bus masters are supported in the C1 state and the SC2200
will temporarily exit C1 to perform a bus master transaction.
C2 Power State
The SC2200 does not support the C2 power state. All rele-
vant registers and bit fields in the Core Logic are reserved.
C3 Power State
The SC2200 enters the C3 state, when the P_LVL3 register
(F1BAR1+I/O Offset 05h) is read. It exits this state back to
the C0 state (Full Speed or Throttling, depending on the
THT_EN bit) upon:
• An NMI, an unmasked interrupt, or an SMI.
• A bus master request, if enabled via the BM_RLD bit
(F1BAR1+I/O Offset 0Ch[1]).
In this state, the GX1 module is in Suspend Refresh mode
(for details, see the Power Management section of the
AMD Geode™ GX1 Processor Data Book, and Section
6.2.9.5 "Usage Hints" on page 169).
PCI arbitration should be disabled prior entering the C3
state via the ARB_DIS bit in the PM2_CNT register
(F1BAR1+I/O Offset 20h[0]) because a PCI arbitration
event could start after P_LVL3 has been read. After
wakeup ARB_DIS needs to be cleared.