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158 AMD Geode™ SC1200/SC1201 Processor Data Book
Core Logic Module
32579B
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 SC1200/SC1201 processor 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 116 and Table 6-5
"Wakeup Events Capability" on page 159.
SC1200/SC1201 processor’s 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.
SC1200/SC1201 processor 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 SC1200/SC1201 processor 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, revision 1.0. These states occur in the Work-
ing state only (S0/G0). They have no meaning when the
system transitions into a Sleep state. For details on the var-
ious Sleep states, see Section 6.2.9.2 "Sleep States" on
page 159.
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 SC1200/SC1201 processor 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 special Halt bus cycle. (See “Usage Hints”
on page 161.)
Bus masters are supported in the C1 state and the
SC1200/SC1201 processor temporarily exits C1 to perform
a bus master transaction.
C2 Power State
The SC1200/SC1201 processor does not support the C2
power state. All relevant registers and bit fields in the Core
Logic are reserved.
C3 Power State
The SC1200/SC1201 processor 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 Throt-
tling, 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 161).
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.