
MOTOROLA
Chapter 10. Power Management
10-5
Programmable Power Modes
To return to full-power mode, one of the following conditions must occur:
Assert core_int, core_smi, or core_mcp internal signals
Decrementer exception interrupt
Hard reset or soft reset
Transition to full-power takes only a few processor cycles. core_qack can remain asserted;
however, core_qreq negates before any bus transaction begins.
10.3.1.5 Sleep Mode
Sleep mode consumes the least amount of power of the four modes, since all functional
units are disabled. To conserve the maximum amount of power, the PLL and internal
core_sysclk signals can be disabled. Due to the fully static design of the G2 core, the
internal processor state is preserved when no internal clock is present. Because the time
base and decrementer are disabled while the G2 core is in sleep mode, the time base
contents must be updated from an external time base following sleep mode, if accurate
time-of-day maintenance is required.
Before entering sleep mode, the G2 core asserts core_qreq to indicate that it is ready to
disable bus snooping. When the system has ensured that snooping is no longer necessary,
the system logic allows the G2 core to enter sleep mode by asserting core_qack for the
duration of the sleep mode period.
Sleep mode is characterized by the following features:
All functional units disabled (including bus snooping and time base)
All nonessential input receivers disabled
Internal clock regenerators disabled
PLL and core_sysclk can be disabled
To enter sleep mode, the following conditions must occur:
Set sleep bit (HID0[10] = 1), MSR[POW] is set
G2 core asserts core_qreq
System logic asserts core_qack
G2 core enters sleep mode after several processor clocks
To return to full-power mode, the following conditions must occur:
Assert core_int, core_smi, or core_mcp internal signals
Hard reset or soft reset
To return to full-power mode after PLL and core_sysclk are disabled in sleep mode, the
following conditions must occur:
Enable core_sysclk
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